Associations of Body Weight and Waist Circumference with Psychopathology, Substance Use, and Well-Being in an Adult Transdiagnostic Sample

Background: Prior studies have established inconsistent associations between body weight and mental health. However, most work has relied on body mass index (BMI) and examination of a single mental health variable. The present study examined associations of BMI and waist circumference with multiple mental health variables in a transdiagnostic psychiatric sample. Methods: Nursing staff measured waist circumference and calculated the BMI of 742 adults (54.6% female, 45.4% male) presenting for psychiatric treatment. Participants completed the Patient Health Questionnaire (PHQ-9), Generalized Anxiety Disorder Scale (GAD-7), Behavior and Symptom Identification Scale (BASIS-24), and Mental Health Continuum-Short Form (MHC-SF) as part of standard clinical monitoring. Suicide risk was assessed using the clinician-administered Mini International Neuropsychiatric Interview (M.I.N.I.). For curve fit estimation regression models, we entered BMI and waist circumference as independent variables separately; we entered seven dependent variables separately: 1) depression, 2) anxiety, 3) substance use, 4) self-harm, 5) interpersonal functioning, 6) well-being, and 7) suicide risk. Results: Increased BMI was associated with decreased well-being and increased depression. Increased waist circumference was associated with worse interpersonal functioning. Non-linear (quadratic) associations were observed between weight and depression, substance use, self-harm, and suicide. Limitations: Most of the sample was White and only 2.6% was in the underweight category, limiting broad applicability of findings. Cross-sectional design precludes causal attributions. Conclusions: Given associations between well-being, depression, interpersonal functioning, substance use, self-harm, and suicide with weight, findings may be used to inform mental health treatment, particularly by tailoring interventions to high-risk weight categories (underweight, obese) in psychiatric populations.