Factors associated with overweight and obesity in schizophrenia, schizoaffective and bipolar disorders

• We examine predictors of elevated BMI across diagnoses in psychotic disorders.
• Affective components of illness were significantly associated with elevated BMI.
• Major depressive episode and suicide attempts predicted BMI≥25.
• Patients with schizoaffective disorder had a greater risk for obesity.

Evidence suggests abnormal bioenergetic status throughout the body in psychotic disorders. The present study examined predictors of elevated body mass index (BMI) across diagnostic categories of schizophrenia, schizoaffective and bipolar disorders. In a cross-sectional study, we studied demographic and clinical risk factors for overweight and obesity in a well-characterized sample of 262 inpatients and outpatients with schizophrenia (n=59), schizoaffective disorder (n=81) and bipolar I disorder (n=122). Across the three diagnostic categories, the prevalence of overweight (29.4%) and obesity (33.2%) combined was 62.6% (164/262). Logistic regression analyses, adjusted for age, sex and ethnicity, showed that schizoaffective disorder, lifetime major depressive episode, presence of prior suicide attempt, and more than 5 lifetime hospitalizations were significantly associated with BMI≥25. Patients with schizophrenia had significantly lower risk for overweight and obesity. Overall, we found that affective components of illness were associated with elevated BMI in our cross-diagnostic sample. Our results show that patients with schizoaffective disorder have a greater risk for obesity. Identifying predictors of elevated BMI in patients with psychotic and mood disorders will help prevent obesity and related cardiovascular and cerebral complications. Future studies are needed to elucidate the mechanistic nature of the relationship between obesity and psychiatric illness.