Evidence for the independent familial transmission of attention deficit hyperactivity disorder and learning disabilities: results from a family genetic study

OBJECTIVE: The purpose of the study was to clarify the relationship between attention deficit hyperactivity disorder and learning disabilities. METHOD: The authors assessed learning disabilities in a sample of 140 children with attention deficit hyperactivity disorder and in 120 normal comparison children. They also assessed a sample of the probands' 822 first-degree relatives. RESULTS: The risk for learning disabilities was highest among relatives of probands with both attention deficit hyperactivity disorder and learning disabilities. The two disorders did not cosegregate in families. There was nonrandom mating between spouses with attention deficit hyperactivity disorder and learning disabilities. CONCLUSIONS: The two disorders are transmitted independently in families, and their co-occurrence may be due to nonrandom mating. Attention deficit hyperactivity disorder is likely to be etiologically independent from learning disabilities.