Longitudinal Associations between ADHD and Weight from Birth to Adolescence

ADHD is associated with lower birth weight, but also with obesity in childhood. Findings on the direction of this association are mixed. This study investigated the relationship between weight and ADHD from birth across development.

We used data from the Millennium Cohort Study (MCS), collected at seven time points between 9 months and 17 years. ADHD diagnosis status and scores on the Strength and Difficulties Questionnaire (SDQ) were used to create an ADHD group and a control group. Random intercept cross-lagged panel models were conducted in females (N=4051) and males (N=3857) to examine bidirectional associations between BMI z-scores and SDQ scores between ages three and 17. Analyses were adjusted for common risk factors for ADHD and obesity, such as sex assigned at birth, multiple births, and ADHD medication status.

Children in the ADHD group were significantly lighter at birth than the control group (t(5674)=2.65, 95% CI [0.02, 0.14] p=.008) and significantly more likely to have obesity at age five onwards (OR range 1.57-2.46, RR range 0.98-2.29). Path analyses conducted separately for males and females showed that higher ADHD symptoms in females at ages 7, 11 and 14 significantly predicted higher BMI z-score at ages 11, 14 and 17 respectively. In males, this association was only seen between age 11 and 14 (β= 0.07; 95% CI, 0.04-0.10, p < .001).

Results suggest that interventions for children with ADHD, and their parents, should begin as soon as possible, prenatally if possible. Developmental sex differences should be considered.