Temperament and character profiles and the dopamine D4 receptor gene in ADHD.

OBJECTIVE This study was designed to investigate the link among attention deficit hyperactivity disorder (ADHD) in adults, novelty-seeking temperament, and the 48-base pair (bp) dopamine D4 receptor (DRD4) gene variant. METHOD This study drew from a larger molecular genetic study of ADHD in which the ascertainment criterion was having an affected sibling pair with ADHD. Parents (N=171) from 96 families provided data. Of the 171 parents, 56 (33%) had a lifetime history of ADHD, with 28 (50%) continuing to meet DSM-IV criteria (i.e., "persistent" ADHD). Latent variable modeling was used to test whether the DRD4 gene variant or Temperament and Character Inventory factors could predict ADHD. RESULTS Using latent variable modeling, the authors were able to confirm the first-order factor structure of the Temperament and Character Inventory. Furthermore, novelty seeking predicted ADHD lifetime diagnosis (R(2)=26%), while the DRD4 gene variant independently predicted ADHD (R(2)=5%) but not novelty seeking. CONCLUSIONS In this unique sample of parents from multiply affected ADHD families, novelty seeking and the 48-bp DRD4 variant were associated with a lifetime history of ADHD. However, the association between novelty seeking and ADHD does not appear to be due to variation in the 48-bp DRD4 variant.