Systematic Review and Meta-Analysis of the Placebo Effect in Panic Disorder: Implications for Research and Clinical Practice Publisher Pubmed



Ahmadzadasl M^{1, 2} ; Davoudi F³ ; Mohamadi S⁴ ; Hadi F⁴ ; Nejadghaderi SA⁵ ; Mirbehbahani SH⁵ ; Jabbarinejad R⁶ ; Saneh S⁴ ; Arshadi M⁷ ; Naserbakht M⁴ ; Sinyor M^{1, 2} ; Kabir A⁸ ; Shamshiri A⁹ Show Affiliations
Source: Australian and New Zealand Journal of Psychiatry Published:2022

Abstract

Objective: This review aimed to measure the degree of placebo response in panic disorder. Data Sources: We searched major databases up to 31 January 2021, for randomized pharmacotherapy trials published in English. Study Selection: A total of 43 studies met inclusion criteria to be in the analysis (with 174 separate outcome measurements). Data Extraction: Changes in outcome measures from baseline in the placebo group were used to estimate modified Cohen’s d effect size. Results: A total of 43 trials (2392 subjects, 174 outcomes using 27 rating scales) were included in the meta-analysis. Overall placebo effect size was 0.57 (95% confidence interval = [0.50, 0.64]), heterogeneity (I2: 96.3%). Higher placebo effect size was observed among clinician-rated scales compared to patient reports (0.75 vs 0.35) and among general symptom and anxiety scales compared to panic symptoms and depression scales (0.92 and 0.64 vs 0.56 and 0.54, respectively). There was an upward trend in effect size over the publication period (r = 0.02, p = 0.002) that was only significant among clinician-rated scales (r = 0.02, p = 0.011). There was no significant publication bias, Egger’s test (p = 0.08). Conclusion: We observed a substantial placebo effect size in panic disorder. This effect was more prominent for some aspects of panic disorder psychopathology than for others and was correlated with the source of the assessment and publication year. This finding has implications both for research design, to address the heterogeneity and diversity in placebo responses, and for clinical practice to ensure optimal quality of care. Systematic review registration number: PROSPERO, CRD42019125979. © The Royal Australian and New Zealand College of Psychiatrists 2022.