Antipsychotic drugs might cause acutely occurring, serious side-effects and thus contribute to the increased physical morbidity and mortality observed in patients with severe mental health disorders. We examined this hypothesis by doing a meta-analysis of International Conference on Harmonisation-Good Clinical Practice-defined serious adverse events occurring in placebo-controlled trials of antipsychotics. For this systematic review and meta-analysis, we included randomised controlled trials (RCTs) comparing second-generation antipsychotics with placebo. We searched MEDLINE, Embase, Cochrane CENTRAL, BIOSIS, PsycINFO, PubMed, ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform for trials published in any language from database inception up until Jan 27, 2017. Trials were included without limitations in population (diagnostic category, age, sex, ethnicity), dosing regimen, blinding status, duration, or publication year. Only psychological studies lasting less than 1 day and trials done in mainland China were excluded. We contacted pharmaceutical companies, drug regulatory authorities, and study investigators for additional data. The primary outcome was the number of patients with at least one somatic serious adverse event. We estimated minimum and maximum numbers of patients with the outcome in each study group and synthesised the results with odds ratios (ORs) in a common-effects meta-analysis. This study is registered with PROSPERO, number CRD42016033930. We identified 597 RCTs, comprising 108 664 participants, that met the inclusion criteria. 314 trials (67 642 participants) with details on individual serious adverse events available constituted the main dataset for meta-analysis. 88% of these were 13 weeks (approximately 3 months) or shorter in duration (median 6 weeks, IQR 4-9). At least one somatic serious adverse event occurred in 698 (1·63%) to 862 (2·02%) of 42 600 patients on antipsychotics, and in 343 (1·37%) to 419 (1·67%) of 25 042 patients on placebo. The odds ratios (ORs) were 1·24 (95% CI 1·08-1·42) and 1·24 (1·10-1·41) based on the minimum and maximum estimate, respectively. In predefined subgroup analyses we found evidence suggesting a larger effect in older patients (>65 years; OR 1·56, 95% CI 1·22-1·98; 1·58, 1·25-1·99) as compared with adults (18-65 years; 1·09, 0·91-1·29; 1·10, 0·95-1·28); likewise in children or adolescents (<18 years) although the evidence was more uncertain (1·49, 0·81-2·75; 1·54, 0·85-2·77). Of 597 included RCTs, 30 (5%), 358 (60%), and 209 (35%) were rated at high, moderate, or low risk of bias, respectively. τ2 was zero for both analyses of the primary outcome (minimum estimate, maximum estimate). A Bayesian sensitivity analysis using external information on heterogeneity gave similar results. We found evidence that antipsychotics cause short-term somatic serious adverse events on top of somatic serious adverse events occurring independent of treatment. This effect appears to be mainly driven by results in older patients. Hence, clinicians should be aware that antipsychotics are potentially toxic, particularly when treating patients sharing risk factors with the older population. German Ministry of Education and Research.