Co-development of ADHD symptoms and emotional problems from childhood to adulthood: predictors and developmental outcomes

Objective: Attention-deficit/hyperactivity disorder (ADHD) symptoms and emotional problems frequently co-occur and the magnitude of co-occurrence is known to increase across development. Longitudinal cohort data provides opportunities to understand how and why ADHD symptoms co-develop. Method: Data were drawn from the Twins Early Development Study, which included 13945 twin pairs. Emotional problems and ADHD symptoms were parent-reported using the Strengths and Difficulties Questionnaire and Conners’ Parent Rating scales. We modelled the co-development of ADHD symptoms and emotional problems from ages 4 to 21 using joint trajectory analysis.Results: The four-class joint trajectory model of ADHD symptoms and emotional problems provided the best fit to the data. This included patterns such as both traits remaining consistently low, both traits steadily increasing, and one trait being high while the other remained low. ADHD and externalizing problems polygenic scores, as well as maternal depression, socioeconomic status and home chaos were significant predictors of the joint trajectory of ADHD and emotional problems. The group with consistently low symptoms reported higher educational attainment, fewer emotional problems, and fewer ADHD symptoms at age 26 than the other groups. Individuals with high initial ADHD symptoms in childhood or increasing symptoms from childhood to adulthood reported lowest educational attainment and socioeconomic status in adulthood among all the groups.Conclusion: Our findings suggest that the co-occurrence of ADHD symptoms and emotional problems can follow various developmental trajectories, and these trajectories have distinct early-life predictors and adult outcomes. We discuss these differences with a view to informing intervention targets.