Semaglutide Helps Schizophrenia Patients Lose Weight Without Side Effects

A study led by researchers from the University of Queensland has shown that semaglutide, the active component in weight-loss medications such as Ozempic and Wegovy, is effective in promoting weight loss in people with schizophrenia without negatively impacting psychotic symptoms.

Addressing weight gain from antipsychotics

Professor Dan Siskind, a psychiatrist and lead researcher, explained that the 36-week trial demonstrated the efficacy of semaglutide in people with schizophrenia, a population often affected by weight gain as a side effect of antipsychotic medications. He noted that some patients discontinue treatments like clozapine due to these weight-related side effects, making this finding particularly significant for clinical treatment strategies.

“People with schizophrenia have a 16-year life expectancy gap compared to the general population which is driven largely by obesity-related illnesses. The study participants on semaglutide lost almost 14 per cent of their bodyweight across the trial, compared to those taking a placebo."

Professor Dan Siskind.

A first-of-its-kind study

This study was investigator-led, meaning it was conducted independently, without involvement from any pharmaceutical companies. Professor Siskind emphasized the importance of this aspect, noting that prior to this research, there was uncertainty about whether semaglutide could interact with other medications or affect mental health.

“We were able to show that semaglutide didn’t affect psychotic symptoms or levels of anti-psychotic medications, indicating that it doesn’t worsen their psychosis. We found no increased risk or drug interactions. The lean mass/fat mass ratio also improved in the semaglutide group, suggesting more fat was lost than non-fatty tissues such as muscle.’’

Professor Dan Siskind.

Advocacy for wider access to semaglutide

Although semaglutide is available in Australia for other conditions, it is not yet listed on the Pharmaceutical Benefits Scheme (PBS) for weight loss. Professor Siskind called for its inclusion, stating that many people with schizophrenia struggle to afford the treatment without PBS support.

"People with schizophrenia urgently need access to effective treatments for obesity, such as semaglutide,’’ Siskind said. “We would be strongly advocating for access to PBS listing for semaglutide for this population."

Reference: Siskind D, Baker A, Arnautovska U, et al. Efficacy and safety of semaglutide versus placebo for people with schizophrenia on clozapine with obesity (COaST): a phase 2, multi-centre, participant and investigator- blinded, randomised controlled trial in Australia. Lancet Psychiatry. 2025;12(7):493-503. doi: 10.1016/S2215-0366(25)00129-4

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