Sex Differences in the Association Between Attention-Deficit Hyperactivity Disorder and Physical Diseases in Childhood and Adolescence Using Nationwide Birth Cohorts

OBJECTIVE: To examine the effect of attention-deficit hyperactivity disorder (ADHD) on sex differences in the hazard risk of a physical disease (PD) in childhood and adolescence, per ICD-10 criteria. METHOD: The Danish population born from 1984 to 1995, comprising over 800,000 individuals, was studied for the 13 different ICD-10 PD categories with ADHD as a time-dependent exposure in time-to-event settings. Time from birth to first episode PD, emigration, death, or 31st December 2017, whichever occurred first, was analyzed by use of piecewise Cox models. RESULTS: Individuals with an ADHD diagnosis had higher or similar hazard risk than undiagnosed individuals throughout follow-up. Across all PD categories, baring malignant neoplasms, ADHD-diagnosed individuals had a higher hazard risk from teen age. In the general population, females had higher hazard risk of most PDs from teen age or early adolescence, while males had higher hazard risk in early childhood. Dispersed modification occurred in the hazard difference between sex post-ADHD diagnosis. For eye and adnexa diseases in childhood, males had about a 15% added hazard that of females in the general population, while females had twice the hazard of males among those diagnosed with ADHD. In the general population of young adulthood, females faced a hazard risk of endocrine, nutritional, and metabolic diseases nine times higher than that of males, with an ADHD diagnosis reducing this ratio by half. CONCLUSION: The time-dependent ADHD diagnosis alters sex differences in the vulnerability to certain PD categories at various ages, while ADHD considerably increases vulnerability to all PDs except malignant neoplasms.