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INFLUENCE OF STUDY DESIGN ON TREATMENT RESPONSE IN ANXIETY DISORDER CLINICAL TRIALS
Author(s) -
Rutherford Bret R,
Bailey Veronika S.,
Schneier Franklin R.,
Pott Emily,
Brown Patrick J.,
Roose Steven P.
Publication year - 2015
Publication title -
depression and anxiety
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.634
H-Index - 129
eISSN - 1520-6394
pISSN - 1091-4269
DOI - 10.1002/da.22433
Subject(s) - placebo , panic disorder , generalized anxiety disorder , medicine , clinical trial , anxiety , expectancy theory , psychiatry , anxiety disorder , social anxiety , reuptake inhibitor , psychology , antidepressant , social psychology , alternative medicine , pathology
Objective The influence of study design variables and publication year on response to medication and placebo was investigated in clinical trials for social anxiety disorder (SAD), generalized anxiety disorder (GAD), and panic disorder (PD). Method Hierarchical linear modeling determined whether publication year, treatment assignment (medication vs. placebo), study type (placebo‐controlled or active comparator), study duration, and the number of study visits affected the mean change associated with medication and placebo. Results In the 66 trials examined, the change associated with both medication and placebo increased over time ( t = 4.23, df = 39, P < .001), but average drug–placebo differences decreased over time ( t = −2.04, df = 46, P = .047). More severe baseline illness was associated with greater drug–placebo differences for serotonin norepinephrine reuptake inhibitors (SNRIs, t = 3.46, df = 106, P = .001) and selective serotonin reuptake inhibitors (SSRI, t = 10.37, df = 106, P < .001). Improvement with medication was significantly greater in active‐comparator studies compared to placebo‐controlled trials ( t = 3.41, df = 39, P = .002). A greater number of study visits was associated with greater symptom improvement in PD trials relative to SAD ( t = 2.83, df = 39, P = .008) and GAD ( t = 2.16, df = 39, P = .037). Conclusions Placebo response is substantial in SAD, GAD, and PD trials, and its rise over time has been associated with diminished drug–placebo differences. Study design features that influence treatment response in anxiety disorder trials include patient expectancy, frequency of follow‐up visits, and baseline illness severity.