The association between birth weight, ponderal index, psychotropic medication, and type 2 diabetes in individuals with severe mental illness

Background: Impaired fetal growth may increase vulnerability towards metabolic disturbances associated with some medications. We examined whether birth weight and ponderal index modify the association between psychotropic medication and type 2 diabetes among young adults with severe psychiatric diagnosis. Methods: A total of 36,957 individuals born in Denmark between 1973 and 1983 with a diagnosis of schizophrenia, bipolar disorder, or depression were followed from first diagnosis until 2018. Cox proportional hazard models were applied to analyse risk of type 2 diabetes with use of psychotropic medications and interactions between psychotropic medication and birth weight and ponderal index, respectively. Results: During follow-up, 1575 (4.2%) individuals received a diagnosis of type 2 diabetes. Use of antipsychotic, mood stabilizing and antidepressant medications were associated with higher hazard ratios (HRs) of type 2 diabetes (HRantipsychotics 1.68 [95%CI 1.49-1.90]; HRmood (stabilizing medication) 1.41 [95%CI 1.25-1.59]; HRantide-pressants 2.00 [95%CI 1.68-2.37]), as were a birth weight below 2500 g (HR 1.13 [95%CI 1.01-1.28]), and high ponderal index (HR 1.26 [95%CI 1.11-1.43]). The highest rates of type 2 diabetes for each psychotropic medication category were found in medication users with low birth weight or high ponderal index. However, neither birth weight nor ponderal index significantly modified the association between psychotropic medication and diabetes risk. Conclusion: Psychotropic medication use, birth weight, and ponderal index were risk factors for type 2 diabetes in patients with severe mental illness, but neither birth weight nor ponderal index modified the association between psychotropic medication and type 2 diabetes.