Attention-Deficit/Hyperactivity Disorder Traits in Childhood and Physical Health in Midlife.

Importance: Although attention-deficit/hyperactivity disorder (ADHD) has been associated with various health risks, most research has focused on children and young adults, leaving long-term physical health outcomes of ADHD traits underexplored. Objective: To investigate the association between childhood ADHD traits and physical health outcomes in midlife and the role health risk factors play in this association. Design, Setting, and Participants: This cohort study included data from the nationally representative, population-based 1970 British Cohort Study. The cohort included people born in England, Scotland, and Wales during the same week in 1970, with follow-up data collected over 46 years. Participants were excluded from the analysis if missing data on 1 or more key variables (sex, ADHD traits, social class, and ethnicity) assessed. The data analysis was performed between February and July 2025. Exposure: Attention-deficit/hyperactivity disorder traits at age 10 years as assessed using a validated measure derived from childhood behavior questionnaires. Main Outcomes and Measures: Outcomes were self-reported health conditions, multimorbidity (2 or more co-occurring physical health conditions), and physical health-related disability by age 46 years. Cox proportional hazards models were used to test whether ADHD traits at age 10 years were associated with hazards of multimorbidity up to age 46 years. Health risk factors, including smoking, alcohol use, psychological distress, higher body mass index, and lower educational attainment from age 26 to 46 years, were examined using path models. Results: A total of 10 930 participants were included in the main analyses (all aged 46 years; 51.0% women). Higher childhood ADHD traits were associated with more physical health conditions (b = 0.10; 95% CI, 0.07-0.13), increased odds of physical multimorbidity (odds ratio, 1.14, 95% CI, 1.08-1.19), and greater physical health-related disability (b = 3.17; 95% CI, 2.27-4.07) by age 46 years. There were no sex interactions for physical health conditions and multimorbidity. However, the association between ADHD traits and physical health-related disability showed a larger effect size in women (b = 4.07; 95% CI, 2.67-5.48) than in men (b = 2.37; 95% CI, 1.24-3.51). Participants who had a high likelihood of meeting ADHD criteria in childhood (5.5%) had an estimated probability of 42.1% (95% CI, 38.2%-46.1%) of physical multimorbidity by age 46 years compared with 37.5% (95% CI, 36.6%-38.4%) for those without high ADHD traits. Indirect associations were observed through smoking, psychological distress, and body mass index. Conclusions and Relevance: This cohort study found that high ADHD traits in childhood were associated with poorer physical health outcomes in midlife, with health risk factors explaining part of this association. Addressing modifiable risk factors may help mitigate long-term health disparities in people with ADHD. Intervention is needed across the life course to support the health and well-being of people with ADHD.