Exploring the bidirectional associations of ADHD symptomatology, nutritional status, and body composition in childhood: evidence from a Brazilian Birth Cohort Study.

Background: Attention deficit hyperactivity disorder (ADHD) has been linked to excessive weight; however, the underlying mechanisms of this association are not well understood. To date, the bidirectional associations between ADHD and nutritional status in childhood have been explored in a limited number of studies, with particularly few of those incorporating body composition data. This study aims to evaluate the associations of ADHD symptoms, nutritional status, and body composition in childhood. Methods: We analyzed data from 3940 children from the 2015 Pelotas (Brazil) Birth Cohort at 4 and 6-7 years of age. Linear regression was performed to evaluate the association between ADHD symptoms and nutritional status (weight, height, and body mass index [BMI]) at ages 4 and 6-7, as well as body composition, specifically fat mass (FF) and fat-free mass (FFM) at ages 6-7. Moreover, a cross-lagged panel model (CLPM) analysis between ADHD symptoms and BMI was performed to explore the bidirectional associations. Results: ADHD symptoms were associated with increased height (β 0.01, 95%CI 0.001, 0.026) and FFM (β 0.02, 95%CI 0.008 - 0.035) at age 4, and increased BMI (β0.02, 95%IC 0.002, 0.038), weight (β0. 02, 95%CI 0.005, 0.039), height (β 0.01, 95%CI 0.000, 0.024), and FFM (β 0.02, 95%CI 0.012, 0.040) at ages 6-7. Although the effects observed in the CLPM suggest a bidirectional relationship between ADHD symptoms and BMI, the association did not reach statistical significance. Conclusion: Children with higher ADHD symptoms showed increased growth in weight, height, and BMI. The observed increase in weight and BMI was attributed to greater FFM in these children.