IMPORTANCE Compulsory admissions, defined as admissions against the will of the patient (according to local judicial procedures), have a strong effect on psychiatric patients. In several Western countries, the rate of such admissions is tending to rise. Its reduction is urgently needed. OBJECTIVE To establish which interventions effectively reduce compulsory admissions in adult psychiatric patients in outpatient settings. DATA SOURCES A systematic computerized literature search was performed using EMBASE, MEDLINE, Web of Science, PsycINFO, CINAHL, PubMed (not yet indexed for MEDLINE), Cochrane Central, and Google Scholar. Every database was searched from its inception until April 30, 2015. STUDY SELECTION Randomized clinical trials (RCTs) that studied any kind of intervention designed to reduce compulsory admission rates in adult psychiatric patients (age range, 18-65 years) in outpatient settings were eligible. Eligibility was independently assessed by 2 of us. DATA EXTRACTION AND SYNTHESIS Two of us independently extracted relevant data. The Cochrane Collaboration's tool was used for assessing risk of bias. Overall risk reduction (random-effects estimate) was calculated in the following 4 subgroups of interventions: advance statements, community treatment orders, compliance enhancement, and integrated treatment. MAIN OUTCOMES AND MEASURES Relative risk (RR) was calculated on the basis of the number of patients who had been compulsorily admitted. RESULTS Our meta-analyses included 13 RCTs comprising 2970 psychiatric patients. The meta-analysis of the RCTs on advance statements showed a significant 23%(RR, 0.77; 95% CI, 0.60-0.98; I-2 = 2.2%) (n = 1102) risk reduction in compulsory admissions. In contrast, the RCTs on community treatment orders (RR, 0.95; 95% CI, 0.81-1.10; I-2 = 0.0%) (n = 742), compliance enhancement (RR, 0.52; 95% CI, 0.11-2.37; I-2 = 55.7%) (n = 250), and integrated treatment (RR, 0.71; 95% CI, 0.49-1.02; I-2 = 49.0%) (n = 876) showed no significant risk reduction in compulsory admissions. CONCLUSIONS AND RELEVANCE The meta-analysis of the RCTs on advance statements showed a statistically significant and clinically relevant 23% reduction in compulsory admissions in adult psychiatric patients, whereas the meta-analyses of the RCTs on community treatment orders, compliance enhancement, and integrated treatment showed no evidence of such a reduction. To date, only 13 RCTs have used compulsory admissions as their primary or secondary outcome measure. This demonstrates the need for more research in this field.