Childhood maltreatment in patients with mental illness as a risk factor for obesity

• Exposure to childhood maltreatment (CM) is a relevant risk factor for obesity in individuals with mental illness. • The link between CM and body-mass-index follows a type and time-sensitive pattern of exposure. • Sensitive periods heighten vulnerability to adult obesity in mental illness, potentially guiding mechanistic research. • Findings aid identification of mentally ill individuals with obesity for tailored adversity-informed treatment. Mental illness increases risk for obesity which is often attributed to medications. We assessed the impact of childhood maltreatment on body-mass-index (BMI) and obesity in N = 261 adult psychiatric inpatients and N = 81 controls. There was an increased risk for obesity in psychiatric inpatients compared to controls. Conditioned random forest regression revealed parental abuse at ages 4–5 and peer-related violence at 7–13 as crucial factors in BMI elevation among individuals with mental illness, while type of psychiatric diagnoses, and use of psychotropics were not. Recognizing this link may aid in understanding the mechanisms and the development of strategies to mitigate the risk.