Lancet Psychiatry. 2025 Dec;12(12):893-905. doi: 10.1016/S2215-0366(25)00273-1.
ABSTRACT
BACKGROUND: Second-generation antipsychotics are widely used to treat patients with bipolar spectrum disorders and effectively manage mood symptoms but can often cause substantial weight gain and other metabolic alterations that elevate long-term risks of cardiovascular disease and premature mortality. Metformin has been shown to be safe and efficacious for ameliorating weight gain but has not been evaluated in typical clinical settings or for more than 6 months in this population and is not widely used as standard of care. Therefore, we conducted a pragmatic clinical trial to assess the effect of metformin treatment in young people treated with second-generation antipsychotics who had a bipolar spectrum disorder along with overweight or obesity.
METHODS: In this multi-site, open-label, pragmatic parallel group study, we enrolled overweight or obese youth aged 8-19 years, previously or currently diagnosed with a bipolar spectrum disorder, and treated with or starting a second-generation antipsychotic. Participants were recruited and followed at 64 clinical sites (community-based mental health centres or academic health centres) in the USA. Sites were eligible for participation if they projected an enrolment rate of at least three patients per month and a minimum total number of 90 patients. Participants were randomly assigned (1:1) to the healthy eating and physical activity (LIFE) or the metformin plus LIFE (MET plus LIFE) interventions, within eight strata defined by baseline BMI percentile (overweight [85th to <95th] vs obese [≥95th]); second-generation antipsychotic-naive (starting vs continuing a second-generation antipsychotic at baseline); and sex assigned at birth, and using block randomisation (blocks of six). The co-primary outcomes were change in age-normalised and sex-normalised BMI Z-score at 6 months and 24 months in the intention-to-treat population. People with lived experience with bipolar disorders were involved in the design, conduct, and reporting of this trial. The Patient-Centered Outcomes Research Institute identification was PCS-1406-19276 and the study was registered at ClinicalTrials.gov, NCT02515773, and is completed.
FINDINGS: Between Nov 5, 2015, and Feb 10, 2022, 1633 individuals provided consent for study inclusion, 68 were excluded (26 withdrew before baseline assessments and 42 did not pass screening assessments), and 1565 were randomly assigned (777 assigned to the MET plus LIFE group and 788 assigned to the LIFE group). Data were available from 1252 participants at month 6 (565 in the MET plus LIFE group and 687 in the LIFE group), and 1299 participants at month 24 (579 in the MET plus LIFE group and 720 in the LIFE group). 829 (53%) participants were male and 736 (47%) were female. The mean age of participants was 13·9 years (SD 2·9). 1023 (65%) were White or Caucasian and 290 (19%) were Black or African American. After 6 months and 24 months, assignment to the MET plus LIFE group resulted in greater change in BMI Z-score compared with LIFE alone (month 6: standardised effect size, 0·26 [95% CI 0·15-0·37], p<0·0001; month 24, standardised effect size=0·11 [0·00-0·22]; p=0·047). Among participants taking metformin, 12 attempted suicide once and one attempted suicide twice; among participants not taking metformin, 25 attempted suicide once and three attempted suicide twice. There were no significant differences in proportions of patients with any suicidality during randomised treatment, as assessed using the Patient Health Questionnaire-9 item 9 (MET plus LIFE: 42 [8%] of 519; LIFE: 57 [9%] of 655). Gastrointestinal adverse events were 2-4 times more common in the MET plus LIFE group.
INTERPRETATION: Although its effect on weight is modest, we conclude that for most patients, the benefits of metformin outweigh the risks. The findings from this trial suggest that clinicians should consider prescribing metformin for young people with bipolar spectrum disorder and related mood disorders who are overweight or obese and are treated with second-generation antipsychotics.
FUNDING: Patient-Centered Outcomes Research Institute.
PMID:41233082 | DOI:10.1016/S2215-0366(25)00273-1
