View Full Version : Genetics of Adult ADHD

09-15-09, 05:48 PM
The role of genetic factors in adult ADHD
Press conference at the 22nd Congress of the European College of Neuropsychopharmacology, Sept. 15, 2009, Istanbul, TurkeyConverging evidence from multiple family and twin studies suggests that ADHD aetiology has a robust genetic component. Heritability estimates range from 60% (Biederman & Faraone, 2005). Heritability and genetic load of the adult form of ADHD appears even higher than that in children: whereas a sibling of a child with ADHD has a 3-fold increased risk for ADHD compared to control children, this risk-increase is 17-fold for a sibling of an adult ADHD patient (Faraone et al., 2000).Meta-analysis of genetic data in IMpACT has, so far, focused mainly on established ADHD genes from studies in children. The gene encoding the dopamine transporter (DAT1), a regulator of signalling through the neurotransmitter dopamine in the brain, has been studied multiple times. Though results have been inconsistent for single genetic variants, a combination of genetic variations at two positions of the gene seems to increase ADHD risk in children. However, in a recent study of 1440 patients and 1769 controls in IMpACT a different combination of variants at the same two positions was found to increase the risk for the persistent, adult form of ADHD. This shows that age is an important factor to be taken into account in genetic association studies in ADHD, and might explain some of the discrepancies between the results of earlier studies (Cormand, Franke et al., presented at the ECNP Congress 2009).

There are a number of interesting things in this press release, but the main thing that struck me was the discussion of research seemingly indicating that the genetic causes of childhood and adult ADHD may be distinct. My understanding of genetics is extremely limited, so I'm not sure what the implications of the specific findings are, and would be interested in hearing from others with a better grasp of such things.