Transdiagnostic effects of combined sleep-circadian interventions on depressive symptoms and sleep outcomes in adults with mental disorders: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVE: Sleep disturbance and circadian rhythm dysregulation are common in mental disorders and may contribute to depressive symptoms and functional impairment. This systematic review and meta-analysis assessed the impact of non-pharmacological interventions targeting sleep and circadian rhythms on depressive symptoms and sleep-related outcomes in adults experiencing mental disorders. METHODS: A comprehensive search was conducted across several databases, including PubMed, Embase, Web of Science, the Cochrane Library, CNKI, VIP, and Wanfang, covering the period from their inception until April 12, 2026. Eligible studies were randomized controlled trials (RCTs) of adults with clinically diagnosed mental disorders receiving combined sleep-circadian interventions. The included populations covered depressive disorders, bipolar disorder, severe mental illness, attention-deficit/hyperactivity disorder, and mixed psychiatric samples. Risk of bias was assessed using the Cochrane RoB 2 tool, and evidence certainty was rated using the GRADE approach. Meta-analyses were carried out with the aid of Review Manager version 5.4. Depending on the context, standardized mean differences (SMDs), mean differences (MDs), or risk ratios (RRs) along with 95% confidence intervals (CIs) were computed. RESULTS: Eleven RCTs were included. Sleep-circadian interventions were associated with reduced depressive symptom severity (SMD = -0.51, 95% CI: -0.72 to -0.30) and higher treatment response (RR = 1.68, 95% CI: 1.25 to 2.27). Remission also favored the intervention groups, but this estimate was based on only two trials (RR = 2.06, 95% CI: 1.09 to 3.90). Improvements were observed in insomnia severity (MD = -5.23, 95% CI: -6.41 to -4.04), sleep disturbance or sleep quality (SMD = -0.92, 95% CI: -1.19 to -0.65), sleep-related impairment (MD = -7.91, 95% CI: -9.89 to -5.93), and functional impairment (MD = -4.78, 95% CI: -6.42 to -3.15). Evidence certainty ranged from very low to moderate, and several outcomes were supported by few trials. CONCLUSION: Sleep-circadian interventions may improve depressive symptoms, selected sleep outcomes, and functioning in adults with mental disorders. Given the heterogeneity of diagnoses and interventions, these findings should be viewed as promising transdiagnostic evidence. Larger trials with longer follow-up are needed. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO, identifier CRD420261412965.