A nationwide cohort study from Griffith University reports that people with bipolar disorder had significantly lower rates of psychiatric hospitalization during periods when they were taking semaglutide. The paper has been published in Acta Psychiatrica Scandinavica.

Semaglutide is sold as Ozempic and Wegovy and belongs to the glucagon-like peptide-1 receptor agonist class, drugs that are already established treatments for type 2 diabetes and obesity. Their possible effects on bipolar disorder, the researchers note, have remained unclear until now.

Key results

The team, led by Professor Mark Taylor of Griffith's School of Medicine and Dentistry, analyzed Swedish national data covering nearly 15,000 people with bipolar disorder prescribed GLP-1 medications across a 15-year period, 2009 to 2024. Semaglutide use was associated with a 21 percent lower risk of psychiatric hospitalization compared with periods when the same people were not taking GLP-1 medicines.

That within-person design is the part worth noticing. Comparing patients to themselves on and off treatment sidesteps a chunk of the confounding that makes observational psychiatry data so easy to dismiss.

Not the whole drug class

The same pattern did not appear for every GLP-1 medication. Liraglutide and dulaglutide were not associated with a reduced risk of psychiatric hospitalization, which the authors say indicates any potential mental health benefit may not extend across the entire class.

That split is more interesting than a uniform class effect would have been. A finding that applies to one molecule and not its neighbors is harder to explain away as a general artifact of people who take weight-loss drugs being healthier.

The proposed mechanism

Diabetes, obesity and bipolar disorder frequently occur together and may share some underlying biological mechanisms. The researchers suggest GLP-1 signaling could help protect the brain by reducing inflammation, cellular stress and other biological processes associated with bipolar disorder, effects that could potentially contribute to greater mood stability and a lower risk of relapse.

About one in 200 people worldwide, roughly 37 million, live with bipolar disorder according to the latest World Health Organization estimates. A 21 percent signal in a population that size is worth chasing.

Limitations

This is registry data, not a trial, and the reported result is an association rather than a demonstrated effect. The proposed brain mechanism is a hypothesis the study design cannot test.

Where the evidence goes next

Taylor said he hopes the findings will now be examined in a randomized controlled trial, which would provide stronger evidence about whether semaglutide itself can improve psychiatric outcomes in bipolar disorder. Until that trial runs, what exists is a large, well-structured signal and an open question about why one GLP-1 and not the others.