Methods: First, a longitudinal population cohort design was used to assess the association between childhood ADHD (age 7 years) and recurrent depression in young-adulthood (age 18-25 years) in N=8310 individuals in the Avon Longitudinal Study of Parents and Children (ALSPAC). Second, 2-sample Mendelian randomization (MR) analyses examined relationships between genetic liability for ADHD and depression utilising published Genome Wide Association Study (GWAS) data.
Results: Childhood ADHD was associated with an increased risk of recurrent depression in young-adulthood (OR=1.35, 95% CI=1.05-1.73). MR analyses suggested a casual effect of ADHD genetic liability on major depression (OR=1.21, 95% CI=1.12-1.31). MR findings using a broader definition of depression differed, showing a weak influence on depression (OR=1.07, 95% CI=1.02-1.13).
Conclusions: Our findings suggest that ADHD increases risk of depression later in life and are consistent with a causal effect of ADHD genetic liability on subsequent major depression. However, findings were different for more broadly defined depression.
- Mendelian randomization