IMPORTANCEThe placebo effect in depression clinical trials is a substantial factor associated with failure to establish efficacy of novel and repurposed treatments. However, the magnitude of the placebo effect and whether it differs across treatment modalities in treatment-resistant depression (TRD) is unclear.OBJECTIVE To examine the magnitude of the placebo effect in patients with TRD across different treatment modalities and its possible moderators. DATA SOURCESSearches were conducted on MEDLINE, Web of Science, and PsychInfo from inception to June 21, 2021. STUDY SELECTION Randomized clinical trials (RCTs) were included if they recruited patients with TRD and randomized them to a placebo or sham arm and a pharmacotherapy, brain stimulation, or psychotherapy arm. DATA EXTRACTION AND SYNTHESIS Independent reviewers used standard forms for data extraction and quality assessment. Random-effects analyses and standard pairwise meta-analyses were performed. MAIN OUTCOMES AND MEASURES The primary outcome was the Hedges g value for the reported depression scales. Secondary outcomes included moderators assessed via meta-regression and response and remission rates. Heterogeneity was assessed with the I 2 test, and publication bias was evaluated using the Egger test and a funnel plot. Cochrane Risk of Bias Tool was used to estimate risks. RESULTS Fifty RCTs were included involving various types of placebo or sham interventions with a total of 3228 participants (mean [SD] age, 45.8 [6.0] years; 1769 [54.8%] female). The pooledplacebo effect size for all modalities was large (g = 1.05; 95% CI, 0.91-1.1); the placebo effect size in RCTs of specific treatment modalities did not significantly differ. Similarly, response and remission rates associated with placebo were comparable across modalities. Heterogeneity was large. Three variables were associated with a larger placebo effect size: open-label prospective treatment before double-blind placebo randomization (β = 0.35; 95% CI, 0.11 to 0.59; P = .004), later year of publication (β = 0.03; 95% CI, 0.003 to 0.05; P = .03), and industry-sponsored trials (β = 0.34; 95% CI, 0.09 to 0.58; P = .007). The number of failed interventions was associated with the probability a smaller placebo effect size (β = −0.12; 95% CI, −0.23 to −0.01, P = .03). The Egger test result was not significant for small studies' effects. (continued) Key Points Question What is the placebo effect magnitude in different treatment modalities used for management of patients with treatment-resistant depression? Findings In this systematic review and meta-analysis of 3228 patients with treatment-resistant depression in 50 randomized clinical trials, the placebo effect size was large and consistent across treatment modalities. Response and remission rates associated with placebo effect were comparable across modalities.Meaning The findings of this study suggest a placebo effect size benchmark may be used to interpret the findings of past and future clinical trials.

Key Points Question Is repetitive transcranial magnetic stimulation associated with changes in subgenual cingulate cortex (SGC) activity in patients with major depressive disorder (MDD)? Findings This diagnostic study, which compared 30 patients with MDD and 30 healthy controls, found that using transcranial magnetic stimulation combined with electroencephalography, SGC activity in patients with MDD was significantly higher compared with healthy controls. After active repetitive transcranial magnetic stimulation, SGC hyperactivity in patients with MDD was attenuated toward the levels of healthy controls. Meaning These SGC-localized findings support SGC hyperactivity as a central construct in the pathophysiology of MDD, which future work might develop into a clinically significant biological target.

Background Mood disorders, i.e. major depressive disorder (MDD) and bipolar disorders, are leading sources of disability worldwide. Currently available treatments do not yield remission in approximately a third of patients with a mood disorder. This is in part because these treatments do not target a specific core pathology underlying these heterogeneous disorders. In recent years, abnormal inflammatory processes have been identified as putative pathophysiological mechanisms and treatment targets in mood disorders, particularly among individuals with treatment-resistant conditions. Aims In this selective review, we aimed to summarise recent advances in the field of immunopsychiatry, including emerging pathophysiological models and findings from treatment ttrials of immunomodulatory agents for both MDD and bipolar disorders. Method We performed a literature review by searching Medline for clinical trials of immunomodulating agents as monotherapy or adjunctive treatments in MDD and bipolar disorders. Included studies are randomised controlled trials (RCTs), cluster RCTs or cross-over trials of immunomodulating agents that had an active comparator or a placebo-arm. Results Current evidence shows an association between inflammation and mood symptoms. However, there is conflicting evidence on whether this link is causal. Conclusions Future studies should focus on identifying specific neurobiological underpinnings for the putative causal association between an activated inflammatory response and mood disorders. Results of these studies are needed before further treatment trials of immunomodulatory agents can be justified.