Background
Attention-deficit/hyperactivity disorder (ADHD) symptoms and emotional problems frequently co-occur. Longitudinal data provide opportunities to understand how and why they co-develop.
Methods
Data were drawn from the Twins Early Development Study, which included 27,890 participants. Emotional problems and ADHD symptoms were parent-reported using the Strengths and Difficulties Questionnaire and Conners’ Parent Rating scales. We modeled the co-development of ADHD symptoms and emotional problems from ages 4 to 21 using joint trajectory analysis. The predictors included polygenic scores (PGSs) for multiple psychiatric symptoms, maternal depression, family chaos, and socioeconomic status (SES). The outcomes included SES, lifetime psychiatric diagnoses, undergraduate diploma attainment, and entry into parenthood at age 26.
Results
A four-class joint trajectory model was selected as best fitting and included: ‘Low ADHD, Low emotional problems’, ‘High-decreasing ADHD, Low emotional problems’, ‘Mid-decreasing ADHD, Increasing emotional problems’, and ‘Increasing ADHD, Increasing emotional problems’. The consistently low-symptom group reported lower ADHD and had lower externalizing PGSs, lower maternal depression, higher SES, and less home chaos at baseline, and higher educational attainment and fewer lifetime depression/anxiety diagnoses at 26 than groups with higher symptom levels. Those with high ADHD symptoms in childhood or increasing ADHD symptoms from childhood to adulthood had the lowest educational attainment and SES in adulthood.
Conclusions
Groups characterized by increasing ADHD symptoms also tended to show increases in emotional problems, whereas increases in emotional problems did not necessarily coincide with increases in ADHD symptoms. The trajectories had distinct early-life predictors and adult outcomes, highlighting potential intervention targets.