Identification of attention-deficit/hyperactivity disorder pedigrees and substance use disorder pedigrees through an ADHD proband sample

Substance use disorder (SUD) pedigrees identified through an attention deficit/hyperactivity disorder (ADHD) proband may be helpful in teasing apart the genetic risks for both ADHD and SUD (ie, alcohol or drug use). Pedigrees segregating for both SUD and ADHD may represent a subset of both of these common disorders that share a related genetic basis. We determined the number of SUD and ADHD pedigrees in a sample of 175 ADHD probands. We found 52 ADHD pedigrees, indicating that at least 29.7% were familial cases. We also found 50 SUD pedigrees; 13 families contained both an alcohol and a drug pedigree, 35 families were alcohol-only pedigrees, and two families were drug-only pedigrees. The incidence of drug-only pedigrees is significantly higher (P<0.01) in families with familial ADHD. This was also true for families with both drug and alcohol pedigrees (P<0.01). The total number of SUD pedigrees and the families with alcohol-alone pedigrees were not significantly different in ADHD pedigrees compared with nonfamilial ADHD families.