TOPLINE:

Among 317,761 patients with type 2 diabetes (T2D) in Scotland, those with a severe mental illness (SMI) were prescribed metformin and insulin sooner after diabetes diagnosis than those without an SMI.

METHODOLOGY:

• Researchers in Scotland conducted a retrospective cohort study to determine whether prescribing glucose-lowering medications to patients with T2D differed by SMI status.
• They analysed data of 317,761 patients (mean age, 60.8 years; 43.6% women) diagnosed with T2D between January 2004 and March 2022, of whom 14,600 had a preexisting SMI.
• A preexisting SMI included schizophrenia, bipolar disorder, or major depressive disorder.
• Outcomes included time from diagnosis of T2D to first metformin and first insulin prescription.
• The median follow-up duration was 1.6 years for patients prescribed metformin and 7.6 years for those prescribed insulin.

TAKEAWAY:

• Patients with an SMI were prescribed metformin and insulin sooner than those without an SMI; at 2 years post−T2D diagnosis, 55.7% of patients with an SMI vs 49.7% of those without an SMI had received metformin, and at 10 years, rates of insulin prescription were 13.3% vs 9.1%.
• Rates of metformin prescription were 9% higher (hazard ratio [HR], 1.09; 95% CI, 1.07-1.11) and those of insulin prescription were 24% higher (HR, 1.24; 95% CI, 1.18-1.31) among patients with an SMI than among those without, after adjusting for age, sex, area-level deprivation, smoking status, year of T2D diagnosis, baseline A1c levels, and estimated glomerular filtration rate.
• Patients with bipolar disorder or major depressive disorder vs those without an SMI had a slightly higher rate of metformin initiation (13% vs 7%) and a substantially higher insulin rate (43% vs 22%); the rate of metformin initiation did not differ between patients with schizophrenia and those without an SMI, but the rate of insulin initiation was lower in the former.

IN PRACTICE:

"Improved integrated mental-physical health care for people with SMI is urgently needed to ensure that health care providers, including primary care physicians and community mental health teams effectively support people with SMI diagnosed with diabetes to achieve optimal self-management, to minimise transition to insulin prescribing and reduce both acute and chronic diabetes complications," the authors wrote. 

SOURCE:

The study was led by Jilly Adams, MPH, Usher Institute, The University of Edinburgh, Edinburgh, Scotland. It was published online on November 14, 2025, in Diabetes, Obesity and Metabolism.

LIMITATIONS:

SMI status was ascertained solely through hospital admission records, so individuals who were never hospitalised may have been missed, potentially attenuating the observed associations. Also, this approach identified predominantly severe cases, limiting generalisability to all adults with SMI. Residual confounding may have persisted, and the study's observational design precluded establishing causal inferences.

DISCLOSURES:

The Scottish Diabetes Research Network received funding from NHS Research Scotland. Two authors were supported by The University of Edinburgh Hub for Metabolic Psychiatry. The authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.