GLP-1 Drugs Help People With Schizophrenia and Bipolar Disorder Lose Weight Without Extra Side Effects | Research

The takeaway

GLP-1 drugs reduced weight by 6 kg and HbA1c by 0.31% in people with severe mental illness, with no increase in dropout rates compared to placebo.

-6.17 kg
Average weight loss with GLP-1 drugs versus placebo in people with severe mental illness across 10 randomized trials

What the researchers found

Across 10 randomized controlled trials with 665 participants, GLP-1 receptor agonists significantly reduced body weight by 6.17 kg (95% CI: -9.10 to -3.25) and HbA1c by 0.31% (95% CI: -0.40 to -0.22) compared to placebo in individuals with severe mental illness (schizophrenia, schizophrenia-spectrum disorders, bipolar disorder).

Critically, dropout rates were no different between GLP-1 RA and placebo groups — both all-cause (RR 0.98) and adverse-effect dropouts (RR 0.99) — indicating acceptable tolerability in this vulnerable population.

Why it matters

People with severe mental illness have dramatically higher rates of obesity and diabetes, largely due to antipsychotic medications that cause significant weight gain. They also die 15–20 years earlier than the general population, primarily from cardiovascular disease. GLP-1 drugs could be transformative for this underserved population — but their safety alongside psychiatric medications needed specific evidence, which this meta-analysis provides.

The numbers in context

10 RCTs · n=665 · Weight loss: -6.17 kg · HbA1c: -0.31% · Dropout RR 0.98 (no difference) · Exenatide, liraglutide, semaglutide studied · I²=91.8% for weight

How the study worked

Systematic review and meta-analysis of randomized controlled trials found in PubMed, Embase, Cochrane Library, Google Scholar, and ClinicalTrials.gov (searched December 2025). Included 10 RCTs of exenatide, liraglutide, or semaglutide in participants with schizophrenia, schizophrenia-spectrum disorders, or bipolar disorder with cardiometabolic risk. Random-effects models estimated mean differences and risk ratios.

Who was studied

665 adults with severe mental illness (schizophrenia, schizophrenia-spectrum disorders, bipolar disorder) and cardiometabolic risk from 10 RCTs

What this study cannot tell us

High heterogeneity for weight outcomes (I²=91.8%) suggests significant variation across trials. Small total sample size (665 participants) limits precision. Evidence certainty was graded as low for efficacy/tolerability and moderate for acceptability. The trials used different GLP-1 RAs at different doses, limiting direct comparisons. Tirzepatide was not included.

How to read the evidence

This is a systematic review and meta-analysis of 10 RCTs — a high-level evidence synthesis. However, the total sample is small (665), heterogeneity is high for the primary weight outcome, and the authors rated evidence certainty as low to moderate using GRADE criteria.

When this study was published

Published in 2026 with a search through December 2025, this is the most current meta-analysis of GLP-1 drugs in severe mental illness, capturing recent semaglutide trials in this population.

The bigger picture

Antipsychotic-induced weight gain is one of the most significant side effects in psychiatry, contributing to the 15-20 year life expectancy gap for people with severe mental illness. GLP-1 drugs represent the most promising pharmacological approach to reversing this weight gain. This meta-analysis provides the evidence psychiatrists need to prescribe these medications with greater confidence.

Questions still open

Do GLP-1 drugs interact with antipsychotic medications in ways that affect psychiatric symptom control?
Would higher-dose or newer GLP-1 drugs (semaglutide 2.4 mg, tirzepatide) produce even greater weight loss in this population?
Could GLP-1 drugs reduce the cardiovascular mortality gap between people with and without severe mental illness?

Common questions

Can people on antipsychotic medications take GLP-1 drugs safely?

This meta-analysis of 10 clinical trials found that GLP-1 drugs were well-tolerated in people with schizophrenia and bipolar disorder. Dropout rates were identical to placebo, suggesting no additional side effect burden when combined with psychiatric medications. However, individual monitoring remains important.

How much weight can people with severe mental illness expect to lose on GLP-1 drugs?

Across the pooled trials, participants lost an average of about 6 kg (13 lbs) more than placebo. This is clinically meaningful and could significantly improve metabolic health, though the range varied considerably between studies. Results may be greater with newer, higher-dose GLP-1 formulations.

Read the original research

Glucagon-Like Peptide-1 Receptor Agonists in Individuals With Severe Mental Illness: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

International journal of psychiatry in medicine, 912174261422822

View on PubMed ↗Publisher’s paper ↗

Citation

Srisurapanont, Manit; Suttajit, Sirijit; Likhitsathian, Surinporn; Suradom, Chawisa; Maneeton, Benchalak. (2026). Glucagon-Like Peptide-1 Receptor Agonists in Individuals With Severe Mental Illness: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. International journal of psychiatry in medicine, 912174261422822. https://doi.org/10.1177/00912174261422822