Preschool development, temperament and genetic liability as early markers of childhood ADHD: A cohort study

BACKGROUND: ADHD is associated with multiple adverse outcomes and early identification is important. The present study sets out to identify early markers and developmental characteristics during the first 30 months of life that are associated with ADHD 6 years later. METHODS: 9201 participants from the prospective Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort were included. Outcome measures were parent‐rated ADHD symptom scores (Strengths and Difficulties Questionnaire, SDQ) and ADHD diagnosis (Development and Wellbeing Assessment, DAWBA) at age 7. Seventeen putative markers were identified from previous literature and included: pre‐ and peri‐natal risk factors, genetic liability (ADHD polygenic risk scores, PRS), early development, temperament scores and regulatory problems. Associations were examined using regression analysis. RESULTS: Univariable regression analysis showed that multiple early life factors were associated with future ADHD outcomes, even after controlling for sex and socio‐economic status. In a multivariable linear regression model; temperament activity scores (B = 0.107, CI = 0.083–0.132), vocabulary delay (B = 0.605, CI = 0.211–0.988), fine motor delay (B = 0.693, CI = 0.360–1.025) and ADHD PRS (B = 0.184, CI = 0.074–0.294) were associated with future symptoms (R (2) = 10.7%). In a multivariable logistic regression model, ADHD PRS (OR = 1.39, CI = 1.10–1.77) and temperament activity scores (OR = 1.09, CI = 1.04–1.16) showed association with ADHD diagnosis. CONCLUSION: As well as male sex and lower socio‐economic status, high temperament activity levels and motor and speech delays in the first 30 months of life, are associated with childhood ADHD. Intriguingly, given that genetic risk scores are known to explain little of the variance of ADHD outcomes, we found that ADHD PRS added useful predictive information. Future research needs to test whether predictive models incorporating aspects of early development and genetic risk scores are useful for predicting ADHD in clinical practice.