Family genetics study questions the role of genetic nurture in ADHD

A substantial study of family genetics indicates that by mid-childhood, a child's ADHD traits are mainly determined by their own genetics, rather than their parents' indirect genetic influence. The research, published in Behavior Genetics, challenges the notion of "genetic nurture" in ADHD. Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition characterized by inattention, hyperactivity, and impulsivity, and it is highly heritable according to numerous twin studies.

The study, led by Daniel L. Wechsler at King’s College London, aimed to separate direct genetic effects from indirect environmental effects caused by parents' genes. The research utilized data from the Norwegian Mother, Father and Child Cohort Study, which included genetic data from mother, father, and child trios and survey data on parental ratings of specific behaviors in their children.

Using a statistical method called trio genome-wide complex trait analysis, the researchers examined a million genetic variations across all three family members. They found at age five, maternal indirect genetic effects accounted for nearly 5% of the variation in children's ADHD traits, while the child's direct genetic effects accounted for less than 2%.

However, when more stringent models were applied, the results were inconclusive, suggesting neither direct nor indirect genetic effects were present at this age due to large margins of error.

At age eight, the analysis showed a clearer pattern, with the child's direct genetics playing a role in their ADHD traits, accounting for about 8% of the variation, while no evidence was found for indirect genetic effects from either parent. This suggests that a child's own DNA is the primary driver of ADHD traits by mid-childhood, challenging the concept of parental genetic nurture in ADHD.