Based on a three-stage stackelberg dynamic game analysis, this paper constructs a product quality control strategy model for three types of distribution channels  in a three-echelon supply chain, which is composed of one manufacturer, one retailer and the final customer. This paper studies how to design a distribution channel strategy and provides a product quality control strategy. Furthermore, this paper analyzes three types of distribution channels strategy in the context of how they influence a manufacturer’s product quality decision and quality prevention strategy, a retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision. We compare the manufacturer’s product quality level, quality prevention effort level, wholesale price, direct sale price and the retailer’s quality inspection effort level, retail price in three types of distribution channels and determine the manufacturer’s and retailer’s expected profits function and the final customer’s consumer surplus. In addition, we introduce the distribution channels demand elasticity ratio to analyze the influence of determining the product quality control strategy. Most importantly, we conduct a numerical sample analysis that will prove the model’s effectiveness and indicate a specific application in practice. In recent years, with the rising of network economy and e-commerce, in addition to the traditional retail channel, more and more customers or consumers choose to purchase products from the internet channel(direct channel), which have become an important way of products sale. With the changing in customer or consumer buying behavior, more and more companies are beginning to redesign or rebuild their distribution channel structure; what’s more, the different types of distribution channels structure in supply chain how to influence the manufacturer’s product quality decision and quality prevention strategy, the retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision; above all, how to influence the manufacturer’s and retailer’s expected profits function and the final customer’s consumer surplus, and how to determine a product quality control strategy in order to eliminate “channel conflict” and “free-riding behavior”. All of these problems and difficulties have not been fully resolved, which are also important research directions for current researchers.In this paper, we will construct a distribution channel strategy model in a three echelon supply chain that is composed of one manufacturer, one retailer and a final customer based on a three-stage stackelberg dynamic game. Furthermore, we will introduce the distribution channel demand elasticity ratio and investigate how to craft a product quality control strategy in three types of distribution channels , which will eliminate the influence of “channel conflict” and “free-riding behavior”. Most important, we will determine the manufacturer’s product quality level, quality prevention effort level, wholesale price, direct sale price, and the retailer’s product quality inspection effort level and retail price, the manufacturer’s and retailer’s expected profits function, and the final customer’s consumer surplus. Then, we will conduct a numerical sample analysis that will indicate a specific application in practice.This paper is chiefly related to three streams of literature. The first stream is the research on how to design a distribution channels structure strategy, the different types of distribution channels structure and how to influence the product quality decision in a supply chain. Yunchuan Liu 2011)  establis  establiThe second stream pertains to designing a product quality contract and establishing a quality incentive mechanism in a supply chain. Peng Ma et al. 2013)  created 13  creatThe third stream of related literature concerns research on product quality risk sharing and the quality strategy of distribution channels in a supply chain. Zhu Lilong et al. (2011)  exploredIn this paper, first of all, we will introduce the distribution channel demand elasticity ratio and investigating how to construct a product quality control strategy model and channel coordination in three types of distribution channels ; what’s more, we consider the manufacturer’s product quality decision and quality prevention strategy, the retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision in a three-echelon supply chain; above all, we also establish a product quality control strategy model in three types of distribution channels to eliminate the influence of “channel conflict” and “free-riding behavior”, which will improve the manufacturer’s and retailer’s expected profits and the final customer’s consumer surplus.The remainder of our paper is organized as follows: in section 3, we describe the model and the basic assumption; in section 4, we consider the product quality strategy in the direct channel and determine the first-best contact parameters; in section 5, we investigate the product quality strategy in the retail channel and establish the manufacturer’s and retailer’s stackelberg “leader-follower” quality control model, and we compare the contract parameter differences with the direct channel. In section 6, we investigate the product quality strategy in the mixed channel that includes a retail channel and a direct channel scenario simultaneously, and in section 7 we present a numerical example analysis to verify our model results. Finally, we provide the research conclusions and direction for future research.qi is the manufacturer’s product quality level; furthermore, i ∈ {D,R,MC} denote the direct channel, the retail channel and the mixed channel respectively. The product quality cost function is k is the manufacturer’s production technology elasticity); so, we assume Ci (0) = Ci′(0) = 0, Ci′(+∞) = +∞, i.e. Ci(qi) is the convex function of increasing marginal cost. λm is the manufacturer’s product quality prevention effort level, and λm ∈ uniform distribution, i.e. a is the final customer lower limit of distribution quantity, b is the final customer upper limit of distribution quantity, and the corresponding final customer’s consumer surplus is (θqi– pi).The final customer’s quality utility is βi is the product demand price elasticity.The final customer’s product demand function will be In this paper, the manufacturer will determine the three types of distribution channels including a direct channel, a retail channel and a mixed channel. The three-stage stackelberg game is in the following order: in stage one, the manufacturer determines the product quality level in a different distribution channel and determines the product quality prevention effort level; in stage two, the manufacturer determines the wholesale price in a retail channel or the direct sale price in a direct channel; and in stage three, the retailer determines the product quality inspection effort level and the retail price.And then, the three types of distribution channels decision system is described as qD, the quality prevention effort level λm and the direct sale price pD.In the direct channel, the manufacturer sells its product to the final customer directly through an internet or online ordering system; then, the manufacturer determines the product quality level, the quality prevention effort level and the direct sale price. Therefore, the manufacturer’s expected profits’ function model is as follows.Proposition 1 In the direct channel, with the final customer’s product demand price elasticity decreases, the manufacturer’s product quality level and direct sale price will increase, and the quality prevention effort level will also increase. In this scenario, the manufacturer’s expected profits’ function is concave; i.e. an optimal product quality level exists that will to be maximum. Then, the final customer’s consumer surplus will increase with the decreasing in the demand price elasticity.Proof. Based on the stackelberg game analysis, this paper will use the backward induction method to solve the equation. Thus, using the first-order and second-order optimal condition with respect to pD in formula (1) yields the following:λm, which yields the following:pD and λmD is the manufacturer’s first-best sales price, and the quality effort level occurs with a direct channel.qD in Thereafter, we use the first-order and second-order optimal conditions with respect to Based on proposition 1, we conclude that, in the direct channel, the manufacturer’s product quality level, the direct sale price and the quality prevention effort level will increase with a decrease in the final customer’s product demand price elasticity. In addition, the manufacturer’s expected profits function is concave, and In the retail channel, the manufacturer sells product to the retailer, which will determine a product quality inspection strategy and then sell the product to the final customer. The manufacturer determines the product quality level, the quality prevention effort level and the wholesale price, and the retailer determines the quality inspection level and the retail price. Therefore, the manufacturer’s and retailer’s stackelberg “leader-follower” control model is described as follows:Proposition 2 In the retail channel, with the final customer’s product demand price elasticity decreases, the manufacturer’s product quality level and wholesale price will increase, and the retailer’s product retail price will also increase. In comparison with the direct channel scenario, the product quality level and the retail price will be much higher.Proof. In this paper, we still use the backward induction method to solve the model. Thus, we use the first-order optimal condition with respect to pR and λr in formula (16), which yields the following:w, and we obtain thatλm, which yields the following:βD = εβR, where ε is the demand elasticity ratio in a different distribution channel condition and ε >1. The demand price elasticity for the direct channel will be greater than for the retail channel; i.e., the final customers are more sensitive to price in the direct channel. Samar K.M (2008) earlier had proved that ηm = ηr.We compare Eqs Based on proposition 2, we conclude that the manufacturer’s product quality level in the retail channel will be much higher than that in the direct channel scenario; the retailer’s retail price will be greater than the wholesale price, which will be also much higher than the manufacturer’s sales price in the direct channel scenario.Corollary 2.1ε > 2).Proof. We compare the manufacturer’s quality prevention effort level and the retailer’s quality inspection effort level in the retail channel with that in the direct channel; then, we determine thatBased on corollary 2.1, we can infer that the manufacturer’s quality prevention effort level in the retail channel will be greater than the retailer’s quality inspection effort level, which will also be greater than the manufacturer’s quality prevention effort level in the direct channel.Corollary 2.2Proof. We substitute formula (25), (26) and (27) into Eqs Based on corollary 2.2, we conclude that the manufacturer’s expected profits in the retail channel will be greater than that in the direct channel scenario.Corollary 2.3.R*CS  > D*CS .Proof. The final customer’s consumer surplus in the retail channel will be described as followsBased on corollary 2.3, we conclude that the final customer’s consumer surplus in the retail channel will be greater than that in the direct channel.T is the transfer payment.In the mixed channel, the manufacturer may sell a product to the final customer directly through an online ordering system or sell wholesale to the retailer who will continue to sell the product to the final customer. Thereafter, the manufacturer will determine a transfer payment to the retailer to eliminate the channel conflict. Therefore, the manufacturer determines the product quality level, the quality prevention effort level, the wholesale price and the direct sale price, and the retailer determines the quality inspection level and the retail price. The manufacturer and the retailer’s stackelberg “leader-follower” control model can be described as follows:Proposition 3 In the mixed channel, in comparison with a direct channel and a retail channel scenario, the manufacturer’s product quality level will be greater than which in the direct channel and less than which in the retail channel, i.e. Proof. We still use the backward induction method to solve the model. Thus, we use the first-order optimal condition with respect to Rp and rλ in formula (32), which yields the following:w and Dp in formula (37) and obtain thatBased on proposition 3, we conclude that, in the mixed channel, the manufacturer’s product quality level will be greater than which in the direct channel and less than which in the retail channel. In addition, the wholesale price will decrease, the manufacturer’s direct sale price will increase and the retailer’s retail price will decrease.Corollary 3.1Proof. We compare the manufacturer’s quality prevention effort level and the retailer’s quality inspection effort level in the mixed channel with which in the direct channel and the retail channel scenario and obtain the following:Based on corollary 3.1, we conclude that, in the mixed channel, the manufacturer’s quality prevention effort level will be greater than that in the retail channel and the direct channel, and the retailer’s quality inspection effort level will be greater than that in the retail channel, which will effectively eliminate the “free-riding behavior.Corollary 3.2Proof. We substitute formula (42), (43) and (44) into Eqs Based on corollary 3.2, we infer that, in the mixed channel, the manufacturer’s expected profits will be less than that in the retail channel but will be greater than the profits in the direct channel; additionally, the retailer’s expected profits will be greater than that in the retail channel.Corollary 3.3Proof. The final customer’s consumer surplus in a mixed channel will be described as followsWe find that Based on corollary 3.3, we can infer that, in the mixed channel, the final customer’s consumer surplus will be greater than that in the retail channel and the direct channel.k = 2, ηm = ηr = 1, α = 60, θ ~ U, T = 120, ε = {2.5, 3.0}, βR ~ . We use numerical computing by Matlab 7.0 and obtain the results, as shown in Tables In this paper, we assume a manufacturer that sells computer components through a retailer (retail channel) or internet online system (direct channel) or through a mixed channel to the final customer. The parameters are described as follows: Based on Based on Based on Tables In this paper, we construct a product quality control model of three types of distribution channel  in a three-echelon supply chain, which is comprised by one manufacturer, one retailer and the final customer, and then we discuss how to design a distribution channel strategy and craft a quality control strategy. Furthermore, our paper analyzes three types of distribution channel strategies regarding how to influence the manufacturer’s product quality decision and quality prevention strategy, the retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision. We compare the product quality level in three types of distribution channels and solve the manufacturer’s and retailer’s expected profits functions and the final customer’s consumer surplus. In addition, we introduce the distribution channel demand elasticity ratio to analyze the influence of determining the product quality control strategy.Our paper demonstrates that, in the direct channel, the manufacturer’s product quality level, the quality prevention effort level and the direct sale price will increase, and the customer’s consumer surplus will also increase with the decreasing in the products demand price elasticity. In addition, in the retail channel which is compared with the direct channel scenario, the manufacturer’s product quality level, the wholesale price, the quality prevention effort level and expected profits will increase, and the retailer’s retail price, the quality inspection effort level and the customer’s consumer surplus will be much higher. In the mixed channel, the manufacturer will determine the transfer payment to eliminate channel conflict, the manufacturer’s quality prevention effort level and the retailer’s quality inspection effort level will increase, which will effectively eliminate the “free-riding behavior”. In addition, the manufacturer’s expected profits will be higher than that in the direct channel and less than that in the retail channel. The retailer’s expected profits and the final consumer surplus will also increase, and our conclusions will be a strong complement to the research field. Most importantly, we conduct a numerical sample analysis that demonstrates the model’s effectiveness and the conclusions’ correctness and will also indicate a specific application in practice.In further research, we will assume that the manufacturer’s quality prevention effort level and the retailer’s quality inspection effort level have incomplete information regarding how to craft a product quality control strategy in three types of distribution channels; then, we will also attempt to construct a multi-stage, repeat and asymmetry information dynamic game model and analyze the distribution channel strategy regarding how to influence the manufacturer’s and retailer’s expected profits function, the final customer’s consumer surplus and social welfare. 8 Jan 2020PONE-D-19-20228Supply Chain Product Quality Control Strategy in Three Types of Distribution ChannelsPLOS ONEDear Authors,Thank you for submitting your manuscript to PLOS ONE. 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If eligible, we will contact you to opt in or out.We look forward to receiving your revised manuscript.Kind regards,Dejan Dragan, PhDAcademic EditorPLOS ONEAdditional Editor Comments (if provided):Editor's initial comments to the paper:Supply Chain Product Quality Control Strategy in Three Types of Distribution ChannelsThe paper deploys a three-stage Stackelberg dynamic game analysis and constructs a product quality control strategy model for three types of distribution channels  in a three-echelon supply chain, which is composed of one manufacturer, one retailer and the final customer. Furthermore, the paper studies how to design a distribution channel strategy and provides a product quality control strategy. Here, three types of distribution channels strategy in the context of how they influence a manufacturer’s product quality decision and prevention strategy, a retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision, are analyzed. The subject of this research is up-to-date and fundamentally interesting for scholars from the field of SCM and OR.The paper, in general, roughly satisfies all rigor requirements that are demanded from Plos One. The red clue remains more or less consistent all over the paper, while the derivations of equations seem to be adequate.However, the editor has detected some major issues based on his own perception, the review of the additional reviewer, and the Plos One criteria for the papers, which should be corrected prior to the further publishing process.Comments of the AE:1. It is not clear enough emphasized what the main contribution of the paper is, i.e., what has been done new, if compared with the work of the other researchers. Here, the borderline should be clearly highlighted, while the main contributions  should be more explicitly given in the introduction and other places, where necessary.2. Figure 1 should be improved in the sense of informative content meaning that the reader immediately understands the main point without even looking at the corresponding text.Comments regarding the Plos One criteria for the papers:http://journals.plos.org/plosone/s/submission-guidelines#loc-methods-software-databases-and-tools. 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Is the manuscript presented in an intelligible fashion and written in standard English?PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.Reviewer #1: No**********5. Review Comments to the AuthorPlease use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. Reviewer #1: 1. The language of the article should be more concise and accurate.2. It is better to complement the differences between this study and the existing research literature.3. The conclusions of the study for the the objectives mentioned in the abstract as ‘This paper studies how to design a distribution channel strategy and provides a product quality control strategy’ are not very clear.4. In this article, we can not see how consumer utility and consumer behavior affect product market demand.5. In Mixed Channel, how does the product demand between the two channels affect each other?**********what does this mean?). If published, this will include your full peer review and any attached files.6. PLOS authors have the option to publish the peer review history of their article  digital diagnostic tool, AttachmentEditor - initial review.docxSubmitted filename: Click here for additional data file.AttachmentReviewer 1 Comments.pdfSubmitted filename: Click here for additional data file. 2 Feb 2020Responses to Editors and ReviewersDear Professor Dejan Dragan and Reviewers,Thank you very much for your suggestions and critical comments about our paper submitted to PLOS ONE (Manuscript ID: PONE-D-19-20228). The revised title is “Supply Chain Product Quality Control Strategy in Three Types of Distribution Channels”.We are also thankful to the reviewers for their critical reading and valuable comments on the manuscript. Those comments were very helpful for providing direction for our further studies. We have tried our best to revise our manuscript according to the comments. Attached, please find the revised version, which we would like to resubmit for your kind consideration. The main revised parts are marked in blue in the paper. The following is a detailed explanation how we have complied with the editor’s and reviewers’ suggestions.Responds to the editor’s comments:Comment #1:The paper deploys a three-stage Stackelberg dynamic game analysis and constructs a product quality control strategy model for three types of distribution channels  in a three-echelon supply chain, which is composed of one manufacturer, one retailer and the final customer. Furthermore, the paper studies how to design a distribution channel strategy and provides a product quality control strategy. Here, three types of distribution channels strategy in the context of how they influence a manufacturer’s product quality decision and prevention strategy, a retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision, are analyzed. The subject of this research is up-to-date and fundamentally interesting for scholars from the field of SCM and OR.The paper, in general, roughly satisfies all rigor requirements that are demanded from Plos One. The red clue remains more or less consistent all over the paper, while the derivations of equations seem to be adequate.Response: Thank you very much for the highly praises and the valuable suggestions. Our paper constructs a product quality control strategy model for three types of distribution channels  in a three-echelon supply chain which use a three-stage stackelberg dynamic game analysis, and then, analyzes three types of distribution channels strategy in the context of how they influence a manufacturer’s product quality decision and quality prevention strategy, a retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision. Most importantly, we conduct a numerical sample analysis that will prove the model’s effectiveness and indicate a specific application in practice.Comment #2: It is not clear enough emphasized what the main contribution of the paper is, i.e., what has been done new, if compared with the work of the other researchers. Here, the borderline should be clearly highlighted, while the main contributions  should be more explicitly given in the introduction and other places, where necessary.Response: Thank you very much for the valuable suggestions. We rewrite and emphasize the paper’s main contributions in every paragraph in “2 Related Literature”, just like: (1) Our paper differs from the existing literature by introducing the distribution channel demand elasticity ratio and investigating how to construct a product quality control strategy model and channel coordination in three types of distribution channels  by providing a new perspective. (2) Our model contributes to the product quality control strategy research by constructing a distribution channel model in a three-echelon supply chain which is composed of one manufacturer, one retailer and the final customer based on a three-stage stackelberg dynamic game. Then, the model considers the manufacturer’s product quality decision and quality prevention strategy, the retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision. (3) we also establish a product quality control strategy model in three types of distribution channels to eliminate the influence of “channel conflict” and “free-riding behavior”, which will improve the manufacturer’s and retailer’s expected profits and the final customer’s consumer surplus.Comment #3: Figure 1 should be improved in the sense of informative content meaning that the reader immediately understands the main point without even looking at the corresponding text.Response: Thank you very much for the valuable suggestions. We redraw the Figure 1 Three types of distribution channels decision system which improve in the sense of informative content meaning that the reader immediately understands the main point of our paper.Figure 1 Three types of distribution channels decision systemResponds to the reviewer’s comments:Comment #1:The language of the article should be more concise and accurate.Response: Thank you very much for the valuable suggestions. We made necessary revisions and language editing in the manuscript according to your suggestions, and the English has also been edited by Wiley English Language Editing Services.Comment #2:It is better to complement the differences between this study and the existing research literature.Response: Thank you very much for the valuable suggestions. We rewrite and emphasize the paper’s main contributions in every paragraph in “2 Related Literature”, just like: (1) Our paper differs from the existing literature by introducing the distribution channel demand elasticity ratio and investigating how to construct a product quality control strategy model and channel coordination in three types of distribution channels  by providing a new perspective. (2) Our model contributes to the product quality control strategy research by constructing a distribution channel model in a three-echelon supply chain which is composed of one manufacturer, one retailer and the final customer based on a three-stage stackelberg dynamic game. Then, the model considers the manufacturer’s product quality decision and quality prevention strategy, the retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision. (3) we also establish a product quality control strategy model in three types of distribution channels to eliminate the influence of “channel conflict” and “free-riding behavior”, which will improve the manufacturer’s and retailer’s expected profits and the final customer’s consumer surplus.Comment #3: The conclusions of the study for the objectives mentioned in the abstract as ‘This paper studies how to design a distribution channel strategy and provides a product quality control strategy’ are not very clear.Response: Thank you very much for the valuable suggestions. With the changing in customer or consumer buying behavior, more and more companies are beginning to redesign or rebuild their distribution channel structure, Such as HP, Nike, Lenovo, in addition to focus on the traditional retail channel, have also opened up an internet channel(direct channel); Dell, MI has been focused on internet channel in the past, and now also began selling products in traditional retail channel; and Apple, Haier sell their products in the traditional retail channel and internet channel in the same time, which used a mixed channel structure. In our paper, we will construct a distribution channel strategy model in a three echelon supply chain that is composed of one manufacturer, one retailer and a final customer based on a three-stage stackelberg dynamic game. Furthermore, we will introduce the distribution channel demand elasticity ratio and investigate how to craft a product quality control strategy in three types of distribution channels , Most important, we will determine the manufacturer’s product quality level, quality prevention effort level, wholesale price, direct sale price, and the retailer’s product quality inspection effort level and retail price, the manufacturer’s and retailer’s expected profits function, and the final customer’s consumer surplus.Comment #4: In this article, we can not see how consumer utility and consumer behavior affect product market demand.Response: Thank you very much for the valuable suggestions. In “3 The Model and Assumption”, we describe that the final customer’s quality utility is, and denotes the type of final customer, is the manufacturer’s product quality level; furthermore, denote the direct channel, the retail channel and the mixed channel respectively; then, we assume ～ uniform distribution, and the corresponding final customer’s consumer surplus is. Therefore, in direct channel, we can describe the final customer’s consumer surplus as = = (14)In retail channel, we can describe the final customer’s consumer surplus as = = (30)In mixed channel, we can describe the final customer’s consumer surplus as = + = (52)Comment #5: In Mixed Channel, how does the product demand between the two channels affect each other?Response: Thank you very much for the valuable suggestions. In our paper, we describe the mixed channel that the manufacturer sells their products in the traditional retail channel by the retailer, in the same time, the manufacturer sells their products to the final customer in direct channel (internet channel). The final customer’s product demand function will be ; denotes the market maximum demand, and is the product demand price elasticity. Therefore, In mixed channel, the manufacturer and the retailer’s stackelberg “leader-follower” control model can be described as follows:  = + - - (31) s.t.  = (32)The product demand in retail channel as The product demand in direct channel as  is the manufacturer’s product quality level in mixed channel, is the product demand price elasticity in retail channel, is the product demand price elasticity in direct channel, is the manufacturer’s wholesale price, is the retailer’s retail price, is the direct sale price in a direct channel, the manufacturer’s product quality cost function in direct channel is .We have tried our best to improve the manuscript and made some substantial changes and necessary deletions according to the editors’ and reviewers’ comments. We earnestly appreciate the editors’ and reviewers’ professional work and hope that the corrections will make our manuscript suitable for publication in PLOS ONE. We are looking forward to receiving comments from reviewers in the future.Once again, thank you very much for your valuable comments and suggestions.Best wishes.Yours sincerely,Lilong Zhu (Correspondence)zhulilong2008@126.comE-mail: Tel: + 86 13853193366, Fax: + 86 531 8618 2769School of Management, Shandong University, Ji’nan Shandong, 250100, ChinaCollege of Business, Shandong Normal University, Ji’nan 250014, Shandong, ChinaAttachmentResponse to Reviewers.docSubmitted filename: Click here for additional data file. 16 Mar 2020PONE-D-19-20228R1Supply Chain Product Quality Control Strategy in Three Types of Distribution ChannelsPLOS ONEDear Authors,Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.==============================Please see below==============================https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.We would appreciate receiving your revised manuscript by 29.3.2020. When you are ready to submit your revision, log on to If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocolsTo enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. 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If eligible, we will contact you to opt in or out.We look forward to receiving your revised manuscript.Kind regards,Dejan Dragan, PhDAcademic EditorPLOS ONE[Note: HTML markup is below. Please do not edit.]Reviewers' comments:Reviewer's Responses to QuestionsComments to the Author1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.Reviewer #2: (No Response)Reviewer #3: All comments have been addressed**********2. Is the manuscript technically sound, and do the data support the conclusions?The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. 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It is a very nice thing that the new literature review part is added. But it seems to be to be too detailed. It will be better that the author just mentioned 2~3 related papers and on top of that, provide their own contributions. Moreover, those contributions should be more precise, instead of "..by providing a newperspective.", the author need to be more specific about what exactly the new perspective is.2. The model and assumption need to be more concise and concrete. For example, when the author mentioned the customer type follow a U, it needs more clarify about the value means and the types they are referring to. It will be better if the author check the model and assumption part one more time and provide additional explanation if necessary**********what does this mean?). If published, this will include your full peer review and any attached files.7. PLOS authors have the option to publish the peer review history of their article  digital diagnostic tool,  25 Mar 2020Responses to Editors and ReviewersDear Professor Dejan Dragan and Reviewers,Thank you very much for your suggestions and valuable comments about our paper submitted to PLOS ONE (Manuscript ID: PONE-D-19-20228R1). The manuscript’s title is “Supply Chain Product Quality Control Strategy in Three Types of Distribution Channels”.We are also thankful to the reviewers for their critical reading and valuable comments on the manuscript. Those comments were very helpful for providing direction for our further studies. We have tried our best to revise our manuscript according to the comments. Attached, please find the revised version, which we would like to resubmit for your kind consideration. The main revised parts are marked in red in the paper. The following is a detailed explanation how we have complied with the editor’s and reviewers’ suggestions.Responds to the editor’s comments:Comment:Please include the following items when submitting your revised manuscript:• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.• A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.Response: Thank you very much for the highly praises and the valuable suggestions for this manuscript. According to the editor’s and reviewers’ suggestions, we have completed all the revision which each point raised by the academic editor and reviewers, the file is labeled 'Response to Reviewers'. We have completed a marked-up copy of our manuscript that highlights changes made to the original version, the file is labeled 'Revised Manuscript with Track Changes'. We also have completed an unmarked version of our revised paper without tracked changes, the file is labeled 'Manuscript'.Comment #2: Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.Response: Yes, I would like to make the peer review history publicly available.Responds to the reviewer’s comments:Comment #1:If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.Reviewer #2: (No Response)Reviewer #3: All comments have been addressedResponse: Thank you very much for the valuable suggestions. We have addressed and completed all the revised comments in the new 'Manuscript'.Comment #2:Is the manuscript technically sound, and do the data support the conclusions?The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.Reviewer #2: YesReviewer #3: YesResponse: Thank you very much for the valuable suggestions. In this manuscript, all the data support the conclusions.Comment #3:Has the statistical analysis been performed appropriately and rigorously?Reviewer #2: YesReviewer #3: YesResponse: Thank you very much for the valuable suggestions.Comment #4:Have the authors made all data underlying the findings in their manuscript fully available?Reviewer #2: YesReviewer #3: YesResponse: Thank you very much for the valuable suggestions.Comment #5:Is the manuscript presented in an intelligible fashion and written in standard English?Reviewer #2: YesReviewer #3: YesResponse: Thank you very much for the valuable suggestions. We made necessary revisions and language editing in the manuscript according to your suggestions, and the English has also been edited by Wiley English Language Editing Services.Comment #6:Review Comments to the Author.Reviewer #2: Really, the paper has been greatly improved as all comments provided by all other reviewers in the first round.Reviewer #3: 1. It is a very nice thing that the new literature review part is added. But it seems to be to be too detailed. It will be better that the author just mentioned 2~3 related papers and on top of that, provide their own contributions. Moreover, those contributions should be more precise, instead of ". by providing a new perspective, the author need to be more specific about what exactly the new perspective is.2. The model and assumption need to be more concise and concrete. For example, when the author mentioned the customer type follow a U, it needs more clarify about the value means and the types they are referring to. It will be better if the author check the model and assumption part one more time and provide additional explanation if necessary.Response to Reviewer #2: Thank you very much for the valuable suggestions. We have revised and completed all comments provided by the editor and reviewers in the first round.Response to Reviewer #3: Thank you very much for the valuable suggestions.1. We have revised the literature review part, which is chiefly related to three streams of literature, it seems not to be too detailed, which is mentioned the related papers and on top of that, provide their own contributions. Moreover, those contributions should be more precise as line 150-160.In this paper, first of all, we will introduce the distribution channel demand elasticity ratio and investigating how to construct a product quality control strategy model and channel coordination in three types of distribution channels ; what’s more, we consider the manufacturer’s product quality decision and quality prevention strategy, the retailer’s product pricing decision and quality inspection strategy, and the final customer’s product demand decision in a three-echelon supply chain; above all, we also establish a product quality control strategy model in three types of distribution channels to eliminate the influence of “channel conflict” and “free-riding behavior”, which will improve the manufacturer’s and retailer’s expected profits and the final customer’s consumer surplus.2. We have revised model and assumption more concise and concrete in line 174-l96. For example, The final customer’s quality utility is , and denotes the type of final customer; then, we assume Ɵ~U uniform distribution, i.e. a is the final customer lower limit of distribution quantity, b is the final customer upper limit of distribution quantity, and the corresponding final customer’s consumer surplus is .We have checked the model and assumption part one more time, and then, provided additional explanation more clearly and accurately.We have tried our best to improve the manuscript and made some substantial changes and necessary deletions according to the editors’ and reviewers’ comments. We earnestly appreciate the editors’ and reviewers’ professional work and hope that the corrections will make our manuscript suitable for publication in PLOS ONE. We are looking forward to receiving comments from reviewers in the future.Once again, thank you very much for your valuable comments and suggestions.Best wishes.Sincerely yours,Lilong ZhuAttachmentResponse to Reviewers.docSubmitted filename: Click here for additional data file. 31 Mar 2020Supply Chain Product Quality Control Strategy in Three Types of Distribution ChannelsPONE-D-19-20228R2Dear authors,We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication.https://www.editorialmanager.com/pone/, click the "Update My Information" link at the top of the page, and update your user information. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.Shortly after the formal acceptance letter is sent, an invoice for payment will follow. To ensure an efficient production and billing process, please log into Editorial Manager at onepress@plos.org.If your institution or institutions have a press office, please notify them about your upcoming paper to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, you must inform our press team as soon as possible and no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact With kind regards,Dejan Dragan, PhDAcademic EditorPLOS ONEAdditional Editor Comments :The improvements have been noticeable so that the paper deserves to be published in the Plos One.Reviewers' comments: 6 Apr 2020PONE-D-19-20228R2 Supply Chain Product Quality Control Strategy in Three Types of Distribution Channels Dear Dr. Zhu:I am pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. onepress@plos.org.If your institution or institutions have a press office, please notify them about your upcoming paper at this point, to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact plosone@plos.org. For any other questions or concerns, please email Thank you for submitting your work to PLOS ONE.With kind regards,PLOS ONE Editorial Office Staffon behalf ofDr. Dejan Dragan Academic EditorPLOS ONE


It is a very old conjecture that emotion governs human choice. Early philosophers like Epicurus  and ArisBritish thinkers of the 18th and 19th century were among the most important exponents of psychological hedonism. In a well-known dictum, Bentham , p. 1 leFamously affirming that human rationality or reason could never on its own control behavior, Hume  was equaIn the second half of the 20th century, psychologists and neuroscientists tended  to stayDamasio  argued cThough demonstrating that choice can be controlled by emotions, Damasio  held thaFurthermore, says Damasio , p. 177:These aspects of Damasio's hypothesis are worth discussing, since the SMH, though controversial, has been so influential—and the man behind the hypothesis has not changed his mind. A recent paper (Verweij and Damasio, If we are to believe its originator, the SMH is unable to explain important aspects of the process behind human choice. What Damasio says about the SMH's limitations leaves open the possibility that another neurobiological mechanism will explain how reasoning determines choice. With regard to “sublime achievements,” this may not be the case, however. As we saw, some such deeds may result from the rejection of biological and cultural causation Damasio, , p. 177.Darwin's thinking, for example, has been called sublime (e.g., Vucinich, There is also something in the reasoning process that can make a choice impervious to the effect of emotions, if we are to believe Damasio . He doesDamasio  does claThe present author admires Damasio for his important work in many fields (e.g., Damasio and Maurer, Says Hume , p. 414,No author can answer every query a reader might have, and it is not incumbent upon Damasio to catalog all things that may affect a choice. Yet few questions in psychology have greater fundamental importance than those regarding how we choose. It may be reasonable, then, to ask why emotion can bias choice but not, in Damasio's view, determine it.some room for such freedom.” It may appear from these assertions that Damasio wants to avoid challenging the doctrine of free will. If that is the intention, Damasio should state clearly that in certain situations, a choice is exempt from causality—and ideally, he should explain when this is the case, and why.Furthermore, Verweij and Damasio , p. 3 apAlternatively, Damasio may believe that when, “on the basis of reasoning” (Verweij and Damasio, Damasio , and toA goal is a state we want to reach. Not surprisingly, all generally accepted definitions of “problem” (e.g., Mayer, a problem is an emotional state—it is a state of wanting. Reaching or not reaching a goal state are also typically described as events that elicit emotion [see Overskeid (Robinson et al.  use “wanverskeid ].Reasoning is a way of solving problems. But reason, says Hume , is the Damasio , on the Some people oversell their insights. But might this be a story of underselling? Can the SMH explain more than its originator will admit?GO confirmed being the sole contributor of this work and approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


If a person experiences both loneliness and mental ill health, it may have severe effects on a person’s wellbeing and functioning. This study explored the ways in which loneliness may be entangled with mental ill health and the factors that contribute to the development of such entanglements.The study participants were women from the Northern Finland Birth Cohort 1986 study, who, in 2001–2002, responded to the survey about being very lonely at the age of 15–16. Women (n = 17) were interviewed again at age 27–28 with semi-structured interviews. Data was analysed with thematic analysis.Loneliness and mental ill health formed four types of entanglements: Entanglement 1 (E1): “Loneliness periodically evoked depressive feelings”; E2: “Loneliness and depressive feelings formed an ongoing spiral”; E3: “Loneliness and diagnosed depression/serious emotional disturbance formed periodic spirals;” and E4: “Serious emotional disturbance/mental illness and loneliness formed an ongoing, difficult spiral.” Social adversities like unsafe family environment, lack of close friends, and school violence contributed to the development of Entanglements 1–3. In Entanglement 4, serious mental health disorder caused loneliness.Loneliness was centrally linked to mental health issues in the present study and should be taken into consideration when providing mental health prevention and treatment. Humans are social beings. As such, positive, reciprocal, and meaningful social relationships are at the core of our well-being. They have a positive influence on our mental and physical health  and/or quality  gender(ed) norms and heteronormativity seemed to intensify experiences of loneliness and a sense of not belonging among young people in Northern Finland . We utilized the NFBC1986 data in our earlier large mixed-methods research project on loneliness Rönkä, , and thevery lonely. In 2013, when they were 27–28 years old young adults, home addresses of those 222 persons were tracked, and an invitation letter was sent to them to participate in an interview for an earlier study project by the authors of the present article. As a few addresses were unknown, the invitation letter was eventually sent to 214 cohort members (144 women and 70 men). Forty responded through a web-link included in the letter or via the first author’s work email. Due to scheduling issues, one interviewee withdrew from the study, and 39 interviews were conducted  by the first author of the present article, in the fall of 2013. The interviewees lived throughout Finland, and they chose the interview setting in their hometowns. Out of 39 interviews, 20 took place in the interviewee’s home, and 14 were conducted in public places, such as a library or a coffee house. Three were done over the phone and two via Skype. All interviews were recorded with professional recording device. The interviews were transcribed verbatim by the first author, resulting in 655 A4 pages of transcriptions. The length of the interviews ranged from 24–93 minutes, and the mean interview length was 57 minutes.The study participants both in our earlier research project and in the present study are among those NFBC1986 members who responded to an adolescent questionnaire sent to them when they were 15–16 years old (2001–2002). Altogether, 9,215 cohort members received the questionnaire. It included a one-item self-report on loneliness (“I feel lonely”), with three response alternatives: “being very lonely,” “being sometimes/somewhat lonely,” and “not being lonely at all” during the preceding six months. In total, 7,014  adolescents responded to the loneliness question in 2001–2002, and among those, 222  responded that they were The Regional Ethics Committee of the Northern Ostrobothnia Hospital District reviewed and approved the NFBC1986 study. When adolescents and parents filled in the questionnaires, written informed consent was obtained from them in 2001–2002. Those adolescents and/or their parents, who refused the usage of their data (or their child´s data), were excluded. Separate ethical approval was requested for conducting the qualitative interview data collection among the cohort members. The Regional Ethics Committee of the Northern Ostrobothnia Hospital District approved the qualitative study in 2013. described matters related to mental ill health, ranging from depressive moods to diagnosed depression, or to a different type of serious mental emotional disturbance or illness. Over one third of the women had diagnoses of depression or different kinds of serious mental illnesses.After this coding, the chronological aspects between loneliness and mental ill health were investigated. A chronological description based on the individual stories of these women from childhood to the time of the interview—their young adulthood, was written to a separate word file. Then, a description was conducted from the perspective of loneliness experience with the aim to determine the start of the experience of loneliness and whether it was alleviated or had ended. Following this, the role  of depression or mental ill health was manually “linked and added” to this chronological description. With multiple readings of the interview transcripts it was looked, when depression or other type of mental ill health was first mentioned, when a possible diagnosis was received, its status at the time of the interview, what kind of depression it was, its intensity, and, at a more latent level, the meaning for the participants , loneliness and mental ill health experiences seemed to be entangled in different ways. Among the remaining four women, the two did not seem to be entangled in any clear way, even with the presence of both loneliness and mental ill health experiences.After crafting the stories, specific loneliness–mental ill health entanglements were “revealed” and then examined more carefully. It was noted, that 8 out of 21 women what kind of descriptions of entanglements of loneliness and depression were forming. It was explored whether the stories presented any common features, similarities, or differences among the women and the stories were grouped/thematized accordingly. The criteria for grouping were the severity, continuity, and timing of loneliness and mental ill health, background factors of the women, buffering factors, and ways of alleviating the negative experiences. Based on this, four different loneliness–mental ill-health entanglements were constructed from the data.The final round of analysis and interpretation was conducted with the transcripts of the remaining seventeen women, who themselves expressed, or from whom it was interpreted, that loneliness and depression and mental ill health were entangled. Then it was asked, The analysis focused on 17 women, whose experiences of loneliness were entangled with different type of mental ill health and mental health problems. Among these women, loneliness and depression fluctuated and recurred over the period between adolescence and young, or emerging adulthood (ages 14–28) instead of being at stable, chronic level at all times, yet some of the women’s experiences had alleviated by the time of the interview. For a majority of the women, especially those who had serious mental illness, their experiences of both loneliness and mental ill health were ongoing.four types of entanglements were identified from the data: 1) “Loneliness periodically evoked depressive feelings (three women); 2) “Loneliness and depressive feelings formed an ongoing spiral” (two women); 3) “Loneliness and diagnosed depression/serious emotional disturbance formed periodic spirals” (four women); and the stories of most of the women (eight) belonged to entanglement 4) “Serious emotional disturbance/serious mental illness and loneliness formed an ongoing, difficult spiral.”Based on the analysis of the stories of 17 women, Figure 2.Loneliness periodically evoking depressive feelingsEntanglement 1, where loneliness periodically evoked depressive feelings. Professional help was not sought for these feelings, and things seemed to resolve on their own . This type of depression that loneliness evoked was not “medical.” As a quote from Kirsia continuum, ranging from not-so-severe loneliness to a depressive mood:The stories of three of the women were grouped under Loneliness is sadness. That describes loneliness best. Depressed mood, even hopelessness, is related to it; it feels hopeless, this will never end, this is always going to be like this, there is no way out … But then it is no longer only loneliness, it is also, or more like, depression, not medical depression, but other, like low, depressive mood. (Kirsi)an explicit consequence of loneliness.Loneliness felt depressive; it hurt. It is difficult to describe. It was tough, as I had no one to talk to. I believe that is the reason why I had quite heavy depression eventually. (Tiina)The quote below shows how Tiina’s loneliness evoked depressive feelings and how depression was perceived as Based on our analysis, loneliness was caused mainly by the experienced difficulties in social relationships. There were periods of insecurity in their friendships, leading to the fear of being left out of social circles. These women had relocated many times in their lives, which made it more difficult to maintain friendships and further influencing loneliness. Also, Tiina, who considered non-medical depression a consequence of her loneliness in the quote above, experienced long-term bullying. She contemplated that bullying led to non-diagnosed social phobia, then to loneliness, and, finally, to non-diagnosed depression. She described that she was not good at maintaining contact with other people, which influenced her loneliness.However, the depression and loneliness remained at a “manageable level.” Likely buffers against more serious depression or a depression diagnosis seemed to be rather good relationships with their parent(s), and despite problems with their friends, they had close, meaningful friends who they could talk to and confine in about their problems.Entanglement 2, loneliness and depressive feelings formed an ongoing spiral. Then, loneliness was described as a constant undertone in one’s life, always recurring and re-surfacing; but it did not turn into an over-encompassing experience for them. The root of their loneliness could be traced to their childhood and an unsafe family environment; they grew up in families marred by alcoholism, which greatly affected their lives. Having an unsafe family environment seemed to contribute negatively to their self-esteem. They described being quiet, shy, and insecure and tended to blame loneliness on themselves. Their parent(s)’ alcoholism caused feelings of shame, and even though they had some close friends, they were not able to share with friends their difficulties relating to family life. Thus, in this entanglement, loneliness was caused by an accumulation of difficulties in family life, which in turn evoked strong depressive feelings. These feelings made it difficult to be sociable and approach others, causing further isolation. A continuous spiral—where loneliness reinforced depressive feelings, and depressive feelings reinforced loneliness—was formed. A quote by Tytti exemplifies this spiral:Tytti:Well, in upper secondary school, absolutely, I was lonely. That was then linked to depression and all that. (—) In loneliness, I was really sad and … mmm … little bit like, empty feeling … mmm, I try to get back to that feeling. I knew it would have been easier if I had someone. I felt like something was missing, something was lacking.In Tytti:Yes, they were rather strong. I was not sociable at all, and that it felt bad, but I had no energy or capability of doing anything about it.ARR: You had depressive feelings at that time?Eventually, professional help was sought for depression, but the help from the counsellor or therapist was not seen as useful by these women. Also, they did not receive a diagnosis of depression. At the time of the interview, their loneliness and depression surfaced occasionally.The third loneliness and mental ill health entanglement was more intense than Entanglements 1 and 2. These women received a diagnosis and professional help for their depression or other serious emotional illness or disturbance they described having.It felt like even though I had those couple of close friends, I felt I should have had more. I must have more. Because I knew other people had such big social circles. I guess I did not know back then what kind of person I really was. (Minna)Minna experienced two “separate” loneliness–depression entanglements. First, she experienced a phase of severe loneliness in adolescence, which she linked to depression. She first described how her loneliness–depression entanglement had something to do with puberty. There did not seem to be any other reason why she suddenly isolated herself, was not sociable, and was not able to be with or talk to others. However, in the quote below, she describes her feelings during adolescence, when she compared her social situation with that of others and felt inadequacy vis-à-vis her social circles.This reveals implications about social norms related to friendships and the emergence of loneliness: the kinds of social relations one was supposed to have, and if one cannot have these relationships, then loneliness could emerge or intensify. It seemed that during adolescence, the norm for a girl was to have a couple of close best friends. The latter entanglement was “triggered” several years later and linked to major life changes and losses. She started to isolate herself and soon received a depression diagnosis and started medication. She described her depression and loneliness as now under control, but she is scared that the depression will recur. She is also experiencing strong uncertainties about her future. She also ruminated on whether she should start a family, as she was approaching her 30s, which seemed to be the normative age for Finnish women to think about their future from the perspective of a family.Entanglement 3 were more intense than Minna’s, but they contained some similarities regarding the loneliness–mental ill health entanglement; these two alternated and formed a spiral, which was now resolved. During their school years, these women had very few or no friends; they were very harshly bullied, and one woman also bullied others. School violence made them isolate themselves, and they experienced severe loneliness. Some women described how they turned more inwards in order to protect themselves and cope with everyday difficulties. For instance, they “shut down” in the context of school; they put their headphones on, put hoodies low on their head, and tried to be as invisible as possible. They did not speak or respond to peers. This type of “armour” made them indifferent to the bullying conducted by others. Still, it did not reduce the bullying, and their loneliness and mental ill-being continued. Also, they behaved and dressed differently from their peers and did not follow the normative femininities in their contexts, which was the main reason they were targeted. Furthermore, substance abuse was common among these women, which started at a very young age. Finally, these women described having poor or mentally and physically abusive relationships with their (step)parents. One women later experienced domestic violence. The women felt that they were unable to share their family-related difficulties with anyone else, which intensified their loneliness. All these accumulated adversities formed a negative spiral that was later linked to a variety of mental health issues and, thus, were likely “triggers” for different diagnoses.The other women’s stories in However, at the time of the interview, these women revealed that they were no longer lonely and that their mental health issues were under control. Contributory factors and buffers against continuing mental health issues included escaping from abusive relationships, getting therapy, undergoing treatment for substance abuse, and finding a partner and starting a family. Relocation also played a strong role in these stories; relocating with a fresh start contributed positively to their current well-being.Entanglement 4. The severe mental health problems that they experienced seemed to influence their social life and contributed or caused their loneliness. The illnesses they described were Asperger’s syndrome, autism, attention deficit disorder (ADD), ADHD, generalized anxiety disorder, severe depression, borderline personality disorder (BPD), and schizophrenia. Also, one woman had anorexia in her adolescence. Among these women, mental health problems were ongoing, and co-morbidity was common. At the time of the interview, the women were also in treatment.Most of the women in this study belonged to The women who had an ADHD diagnosis experienced difficulties in their social relationships from early on. They were having difficulties in understanding and acting upon social and behavioural norms in the school context. They were also harshly bullied at school and had no close friends. One woman with these issues described that she acted out violently in school when others were “pushing her buttons,” when they irritated and bullied her. This caused many difficulties for her, and she had to change schools several times over the years. With this type of behaviour, she did not follow the rules and behavioural norms in the context of school, especially those assigned for girls. Also, outside school, some of the women were behaving delinquently, and had substance abuse problems. Furthermore, a couple of women in this Entanglement described being a part of different types of sub-cultures. They had dyed their hair, underwent piercings, later tattoos, and dressed up differently from others. They stood out from the typical adolescent in Northern Finland and did not follow the typical femininities assigned to girls in their contexts. Similar to the previous entanglement, they were targets of school violence, which intensified their loneliness and mental health issues.It would be nice to be able to have a sense of belongingness with so-called neurotypical people, but our worlds are so different. It is difficult … a sense of non-belongingness has characterized my whole life. I just feel like I do not belong to this world at all, that I am so different, and somehow, I feel like others cannot understand me and I cannot understand others … It feels like I am from a different planet, that I do not belong on this planet. This world is made for a different kind of people. And sort of, how to describe this: The others are like roses, and I am like a thistle. (Jaana)Jaana was only recently diagnosed with ADD and Asperger’s syndrome, even though these symptoms had affected much her over the course of her life, causing constant difficulties in multiple ways. In the quote below, she explains how she feels about not being “neurotypical,” the word she uses for those without ADD and Asperger’s syndrome. Not belonging has characterized her whole life, and she feels different from others. All this is intertwined with experiencing loneliness.More seriously, mental health issues entangled with loneliness were linked with suicidal behaviour. One woman was diagnosed with BPD disorder. Loneliness and a sense of not belonging, the latter being a symptom of BPD, has been a constant recurrence in her life. Some years ago, she tried to commit suicide twice.Entanglement 4 were the main contributors to loneliness and not so much other way around. Also, contrary to the women in Entanglements 2 and 3, these women had parents who supported them and were trying their best to help their children with these difficulties. This has likely been very important for their lives, like the case of the woman with BPD, who described how she could always count on her parents in the most difficult phases of her illness. However, despite the efforts of their parents, their issues continued.Based on our interpretation, the severe mental health difficulties in how these two negative experiences were entangled with each other over time and show how both difficult experiences may alleviate, at least momentarily. According to the findings, the co-existence of loneliness with different types of mental ill health was strikingly common. As many as 66% of the interviewees talked about their mental health issues. Additionally, more than one-third had a mental health diagnosis. These numbers among lonely women were much higher than, for instance, the prevalence (5.6%) of diagnosed depression disorders in the general adult population in Finland . It was very difficult for those women with severe mental difficulties or neuropsychiatric problems to approach others or to form and maintain social relationships. In general, they had difficulty following social codes and social norms and tired easily in social situations. They did not follow the “social games” that other peers “performed” at school. This contributed to feelings of non-belongingness, a lack of and need for close and meaningful friends, and experienced loneliness.Contrary to common assumptions, earlier studies on ASD have also shown how young people with ASD are oftentimes aware of their problems with social integration Attwood,  and repoAlso, associations between loneliness and ADHD/ADD have been explored in recent studies. Studies have documented that children and adolescents with these symptoms and diagnoses were more likely to experience difficulties in their peer relationships and have few or no friends Hoza, . In the Besides mental ill health, unsafe family environments characterized by substance abuse, physical and emotional violence, or otherwise difficult relationships with parents, was alarmingly common among the lonely women in this study, and seemed to contribute significantly to loneliness–mental ill health Entanglements 2 and 3. The psychodynamic theory of loneliness, influenced by Freud’s general psychotherapeutic approach, posits that loneliness originates from problems and distortions in early emotional bonds with early attachment figures. Problems with these relationships contribute to inadequate interaction skills and further problems that manifest as difficulties in creating friendships, thus causing loneliness. Earlier studies on mental ill health have also indicated that depression in adolescence may be strongly linked to dysfunctional family relationships and that depressed youth commonly report lower levels of family cohesion and closeness, lower levels of support, more conflicts, more parental control, and poorer communication  norms, normativities and related acts, as well as repetition and citation based “doing of gender” as influencing the social realm of women Butler, , 2015 anNegative social factors were common triggers for loneliness–mental ill health entanglements, but positive social factors were, in turn, important buffers against further difficulties among some of the women. Our findings indicate that in Entanglements 1 and 3, the women had some friends to talk to about their lives and problems. Indications of this were found in previous research conducted among both bullied and lonely youth; having at least one friend may be an important buffer against further emotional or psychological problems , and who volunteered at age 27–28 to the interview to discuss about the topic further. The data on these women offered very interesting and important possibilities to explore the entanglements, specifically between loneliness and mental ill health, even though they did not represent a typical group of young, or emerging adults from Northern Finland, or the entirety of lonely young adults. Some of the interviewees also expressed their willingness to help other people—researchers and other young people alike—by participating in the interview. Many of them were also familiar with talking about their problems to psychologists, therapists, or healthcare professionals. This is not necessarily a limitation. Time had passed from the difficult times in their lives, and they now had room to contemplate and discuss their experience in the interview in a very informative way.Another limitation is that only one interview with each participant was conducted. Multiple interviews could have yielded a more nuanced picture of loneliness. We were expecting to conduct about 20 interviews, but more cohort participant volunteered than expected, and as many as 39 interviewees were finally conducted. As the interviewees lived across the country, with limited resources, only a one-time interview was feasible. However, the participants openly discussed their sensitive experiences in the interviews, and a trusting atmosphere was deemed to have been formed in the interview situations, which can be considered as an important strength of the present study.Unsafe conditions in the childhood home; experienced violence during one’s life, influenced by gender(ed) norms and normativities; and a lack of meaningful social interactions  wThe study underlines how the accumulation of different difficulties may contribute to many socioemotional and mental health problems in a person’s life. The four types of entanglements revealed may be tested in future studies in order to explore whether similar types of entanglements can be found among young people in other contexts and countries and whether these four types help in better understanding and explaining the relationship between loneliness and mental ill health. Furthermore, future studies regarding loneliness and mental health should focus on the gendered aspects of both experiences. For instance, not many studies have focused especially on boys’ or men’s loneliness or depression experiences. Also non-binary gender categories should be included in the research of loneliness and mental ill health, in order to observe the experiences of young people who do not identify themselves within these categories. Furthermore, the methods used for exploring these issues could be more varied and creative, utilizing other data production methods besides interviews.Implications for future policy and practiceThe findings of the present study have relevance for social, health, and family policies and practices. According to the findings, social problems and loneliness, both in peer contexts as as problems within families, are pivotal to mental health issues. Even children can experience social and mental health problems. When a child or adolescent experiences loneliness for lengthy periods, for instance, longer than a couple of months, it is prudent to explore the issues behind their loneliness and try to alleviate the experience before it exacerbates.Adequate government funding of health and social services is important in order to offer possibilities for receiving timely support and mental health treatment. Maternity and child health clinics are also important services regarding early prevention, and professionals working there should be aware of issues related to loneliness and mental health and be able to identify families at risk and offer them low-threshold supportfrom early on. Also, parents and other adults in the lives children and adolescents, such as teachers, should be aware of loneliness and its likely effects. These issues should be discussed in teacher–parent meetings as well as in parental events in early education and comprehensive school.The present study emphasizes that having different types of severe mental ill health, ASD, or neuropsychiatric issues may be a strong risk factor in developing loneliness. Close attention should be paid to the social realm of young people with these difficulties. These youth may still have a strong need for and sense of belonging , and it is important to find ways to support their social relationships and them possibilities for finding meaningful reciprocal social relationships in different contexts, such as at home and school.Furthermore, tackling school violence is of utmost importance in reducing the loneliness experience, the further negative accumulation of difficulties, and the formation of loneliness–mental ill health entanglements. Whole-school approaches have proven most effective in tackling school violence, but they seem to be most effective in primary school environments  contributed to the development of loneliness, school violence, and mental health issues. It is important to deconstruct these detrimental and limiting norms, allow children and adolescents to live up to their full potential, and offer young people possibilities to be themselves. Educational policies and schools should more strongly and comprehensively advocate multidimensional equality within school contexts and offer teachers and parents practical tools for discussing and promoting these issues with pupils in their everyday school life. For instance, arts-based interventions could be useful in promoting empathy and further enhance social and mental well-being