Objective: Patient expectancies are hypothesized to contribute to the efficacy and side effects of psychiatric treatments, but little research has investigated this hypothesis in the context of psychopharmacological therapies for anxiety. We prospectively investigated whether expectancies predicted efficacy and adverse events in oral therapy for Generalized Anxiety Disorder (GAD), controlling for confounding patient characteristics correlating with outcomes.
Methods: Expectancies regarding treatment efficacy and side effects were assessed at baseline of an eight week open-label phase of a trial of chamomile for Generalized Anxiety Disorder (GAD). The primary outcome was patient-reported GAD-7 scores, with clinical response and treatment-emergent side-effects as secondary outcomes. Expectancies were used to predict symptomatic and side-effect outcomes.
Results: Very few baseline patient characteristics predicted either type of expectancy. Controlling for a patient's predicted recovery based on their baseline characteristics, higher efficacy expectancies at baseline predicted greater change on the GAD-7 (adjusted β = -0.19, p = 0.011). Efficacy expectancies also predicted a higher likelihood of attaining clinical response (adjusted odds ratio = 1.69, p = 0.002). Patients with higher side effect expectancies reported more side effects (adjusted log expected count = 0.26, p = 0.038). Efficacy expectancies were unrelated to side effect reports (log expected count = -0.05, p = 0.680), and side effect expectancies were unrelated to treatment efficacy (β = 0.08, p = 0.306).
Conclusions: Patients entering chamomile treatment for GAD with more favorable self-generated expectancies for the treatment experience greater improvement and fewer adverse events. Aligning patient expectancies with treatment selections may optimize outcomes.
Registration: Trial Number NCT01072344 at ClinicalTrials.gov.
Keywords: Anxiety; Efficacy; Expectancy; Nocebo; Placebo.
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