DRD4 related to infant attention and information processing: a developmental link to ADHD?

The dopamine D4 receptor (DRD4) exon III polymorphism has generated interest because of its association with attention deficit hyperactivity disorder (ADHD), with an increased frequency of the seven-repeat allele being reported in children with ADHD. Deficits in sustained attention and information processing characterize ADHD, and individual differences in these functions are apparent from infancy. We found that in a structured play situation and on an information-processing task, 1-year-old infants with the 7-DRD4 allele showed less sustained attention and novelty preference than do infants without the 7-DRD4 allele. There was also a significant interaction between DRD4 and the serotonin transporter promoter (5-HTTLPR) gene on a measure of sustained attention. Our results provide evidence for a possible developmental link between DRD4 and ADHD via early sustained attention and information processing. It also points to the importance of considering the influence of more than one gene in studies of behavior.