Semaglutide Improves Metabolic Health in Schizophrenia Patients on Antipsychotics

This randomized, placebo-controlled trial evaluated the effects of semaglutide on metabolic outcomes in a high-risk population: overweight or obese individuals with schizophrenia and prediabetes who were receiving second-generation antipsychotics. The study enrolled 154 participants, with 77 randomized to semaglutide 1.0 mg weekly and 77 to placebo. The follow-up period was 30 weeks. The primary outcomes were insulin sensitivity, insulin resistance, and beta-cell function. Secondary outcomes included fasting glucose, body weight, fasting insulin, and C-peptide.

Results showed significant improvements in several metabolic parameters. Fasting glucose was significantly reduced with semaglutide compared to placebo, with a mean difference of -0.87 mmol/L (95% CI -1.15 to -0.59; P < 0.001). Insulin sensitivity improved significantly, with an effect size of 8.60 (95% CI 5.82 to 13.65; P = 0.001). Insulin resistance was also lowered, with an effect size of -0.69 (95% CI -1.00 to -0.20; P = 0.006). Additionally, participants experienced substantial weight loss of 9.2 kg with semaglutide (P value not reported).

Secondary outcomes showed nonsignificant trends. Fasting insulin showed a trend toward reduction (-52.3 pmol/L; P = 0.11), and C-peptide also trended lower (-182.9 pmol/L; P = 0.096). Beta-cell function showed a modest, nonsignificant increase (effect size 8.10; P = 0.19). Importantly, mediation analysis indicated that improvements in insulin sensitivity and insulin resistance were partly mediated by weight loss, with estimates of 7.82 (P = 0.01) and -0.75 (P = 0.01), respectively.

Safety and tolerability data were not reported in the available information. No adverse events, serious adverse events, or discontinuations were described. This limits the ability to assess the risk-benefit profile of semaglutide in this population.

Compared to prior studies in the general population with prediabetes or obesity, semaglutide has shown similar metabolic benefits. However, this trial is notable for focusing on individuals with schizophrenia, a group often excluded from major trials despite high rates of metabolic syndrome due to antipsychotic use. The findings align with previous evidence that GLP-1 receptor agonists can improve glycemic control and promote weight loss, but the specific context of antipsychotic-induced metabolic dysfunction adds new insight.

Methodological limitations include the lack of reported safety data, which is a significant gap. The study also did not specify the setting, funding sources, or conflicts of interest. The sample size was modest, and the follow-up of 30 weeks may be insufficient to assess long-term outcomes. Additionally, the primary outcomes were composite measures, and some secondary outcomes did not reach statistical significance, suggesting the need for larger, longer-term trials.

Clinically, these results support considering semaglutide as a potential strategy for managing metabolic dysfunction in overweight or obese patients with schizophrenia and prediabetes who are on second-generation antipsychotics. The substantial weight loss and improvements in glucose metabolism are encouraging. However, the absence of safety data and the modest sample size mean that clinicians should interpret these findings cautiously and await further confirmatory studies.

Several questions remain unanswered. Long-term efficacy and safety, effects on psychiatric symptoms, optimal dosing, and impact on cardiovascular outcomes are unknown. The role of weight loss as a mediator versus direct metabolic effects of semaglutide also requires further exploration. Future research should include comprehensive safety monitoring and longer follow-up.