Among Multiple Mental Health Symptoms, Only Attention Deficit/Hyperactivity Problems Predict Poorer BMI Outcomes in Family-Based Behavioural Treatment for Youth With Severe Obesity.

Large variability exists in outcome following Family-based treatment (FBT) for severe obesity in youth. In the present study, we aimed to expand our understanding of how mental health impacts FBT outcomes. In total, 90 participants (58.9% girls) 5.9-18.6 years (mean ± SD: 13.2 ± 3.1) were enrolled in a 17-session FBT-programme. Baseline mean percentage above the IOTF threshold for overweight (%IOTF25) was 146 ± 13, and Body Mass Index standard deviation score (BMIz) was 3.02 ± 0.52. Mental health predictors were assessed using the Self-Perception Profile for Children and the Child Behaviour Checklist. A multivariate multilevel Bayesian linear mixed-effects model with repeated measures was utilized to estimate the effects of mental health predictors on BMI outcomes. Average change in BMI during FBT was -3.80 (%IOTF25) and -0.08 (BMIz) units. Higher scores of Attention Deficit/Hyperactivity (ADH) Problems were associated with a smaller reduction in BMI (0.31 units for %IOTF25 (p = 0.02), 0.01 units for BMIz (p = 0.03) for each one-unit T-score increase on the ADH problem scale). Self-Worth, Emotional Dysregulation, Internalizing- and Externalizing problems were not associated with differences in BMI outcomes. Identifying children with higher ADH problems and incorporating additional family support strategies within FBT should be a focus for further treatment development.