Semaglutide Reverses Antipsychotic-Induced Metabolic Harm in Schizophrenia Patients

People with schizophrenia spectrum disorders face a dramatically shortened lifespan, driven in large part by cardiometabolic disease. Second-generation antipsychotics (SGAs) like clozapine and olanzapine — among the most effective psychiatric medications — are notorious for causing rapid weight gain, insulin resistance, prediabetes, and frank type 2 diabetes. Early intervention before metabolic damage becomes entrenched is a largely unexplored therapeutic opportunity.

This multicenter, double-blind, placebo-controlled randomized clinical trial enrolled 73 participants aged 18–65 from three clinical sites in Denmark between September 2021 and August 2024. Eligibility required a schizophrenia spectrum diagnosis, clozapine or olanzapine initiation within the prior 5 years, and early-stage glycemic dysregulation (HbA1c 5.4–7.4%) without current antidiabetic treatment. Participants received once-weekly subcutaneous semaglutide 1 mg or matching placebo for 26 weeks as an adjunct to their existing SGA therapy. The prespecified primary outcome was change in HbA1c from baseline to week 26, analyzed by intention-to-treat. Mean age was 35 years, 65% were female, and mean BMI was 36.1 — reflecting the significant baseline metabolic burden typical of this population.

Semaglutide produced a statistically significant and clinically meaningful reduction in HbA1c compared with placebo (mean difference −0.25%; 95% CI −0.33 to −0.16; P < .001). Strikingly, 43% of participants in the semaglutide group achieved HbA1c levels below 5.4% (considered low risk) versus only 3% in the placebo group. Beyond glycemia, semaglutide drove substantial reductions in body weight (−9.2 kg; 95% CI −13.3 to −5.1; P < .001), waist circumference (−7.0 cm; 95% CI −10.6 to −3.3; P < .001), and fat mass (−6.1 kg; 95% CI −10.2 to −1.9; P = .006). No significant differences were observed in lipid profiles, liver function tests, or blood pressure between groups.

Critically for a psychiatric population, psychiatric symptom severity did not differ between arms, and psychiatric adverse events were similar across groups. Gastrointestinal side effects — the hallmark tolerability concern for GLP-1 receptor agonists — were common in the semaglutide group but described as mild and transient, consistent with the known profile of the drug class. Trial completion was 78% (57 of 73 participants), a reasonable retention rate given the complexity of this patient population.

These results carry broad implications. They demonstrate that early GLP-1 receptor agonist intervention — before metabolic dysregulation progresses to established type 2 diabetes — can substantially reverse antipsychotic-associated glycemic and weight abnormalities without compromising psychiatric stability. Given that cardiovascular disease is the leading cause of premature death in schizophrenia, and that SGA-associated metabolic effects compound underlying genetic and lifestyle risks, semaglutide could serve as a disease-modifying cardiometabolic intervention in this population. The study adds to a growing body of evidence supporting GLP-1 RAs in psychiatric contexts and calls for longer-term trials examining hard cardiovascular endpoints.