Placebo Responses in Genetically Determined XXXX : A Meta-Analysis.

@entity1 @entity717 @entity303 @entity922
BACKGROUND: Genetically determined @entity717 ( @entity717 ) is an intractable condition that involves severe impairment of mental abilities such as learning, reasoning and predicting the future. As of today, little is known about the placebo response in @entity1 with @entity717 . OBJECTIVE: To determine if placebo response exists in @entity1 with genetically determined @entity717 . DATA SOURCES AND STUDY SELECTION: We searched Medline/PubMed, EMBASE, CENTRAL and PsycINFO to find all placebo-controlled double-blind @entity922 ( @entity922 ) in @entity1 with genetically determined @entity717 , published up to April 2013, focusing on core @entity717 symptoms. DATA EXTRACTION AND SYNTHESIS: Two investigators extracted outcome data independently. MAIN OUTCOMES AND MEASURES: Bias-corrected standardized mean difference (Hedge's g) was computed for each outcome measure, using the Comprehensive Meta-Analysis software. A priori defined @entity1 sub-groups were analyzed using a mixed-effect model. The relationship between pre-defined continuous variable moderators (age, IQ, year of publication and trial duration) and effect size was analyzed using meta-regression. RESULTS: Twenty-two placebo-controlled double-blind @entity922 met the inclusion criteria (n = 721, mean age = 17.1 years, 62% @entity1 , mean trial duration = 35 weeks). There was a significant overall placebo response from pre- to post-treatment in @entity1 with @entity717 (g = 0.468, p = 0.002), both for "subjective outcomes" (a third- @entity1 's evaluation of the @entity1 ) (g = 0.563, p = 0.022) and "objective outcomes" (direct evaluation of the @entity1 's abilities) (g = 0.434, p = 0.036). Individuals with higher IQ had higher response to placebo (p = 0.02) and no placebo response was observed in @entity717 @entity1 with comorbid @entity303 . A significant effect of age (p = 0.02) was found, indicating higher placebo responses in treatment of younger @entity1 . CONCLUSIONS AND RELEVANCE: Results suggest that @entity1 with genetically determined @entity717 improve in the placebo arm of @entity922 . Several mechanisms may contribute to placebo effects in @entity717 , including expectancy, implicit learning and "placebo-by-proxy" induced by clinicians/family members. As the condition is refractory, there is little risk that improvements are explained by spontaneous remission. While new avenues for treatment of genetically determined @entity717 are emerging, our results demonstrate how contextual factors can affect clinical outcomes and emphasize the importance of being vigilant on the role of placebos when testing novel treatments in @entity717 .
