The Dopamine D4 Receptor Gene and Moderation of the Association Between Externalizing Behavior and IQ

Department of Psychology, and Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.
Archives of General Psychiatry (Impact Factor: 14.48). 12/2006; 63(12):1410-6. DOI: 10.1001/archpsyc.63.12.1410
Source: OAI


Dopaminergic neurotransmission is implicated in externalizing behavior problems, such as aggression and hyperactivity. Externalizing behavior is known to be negatively associated with cognitive ability. Activation of dopamine D4 receptors appears to inhibit the functioning of the prefrontal cortex, a brain region implicated in cognitive ability. The 7-repeat allele of the dopamine D4 receptor gene produces less efficient receptors, relative to other alleles, and this may alter the effects of dopamine on cognitive function.
To examine the influence of a polymorphism in the third exon of the dopamine D4 receptor gene on the association between externalizing behavior and IQ.
In 1 community sample and 2 clinical samples, the presence or absence of the 7-repeat allele was examined as a moderator of the association between externalizing behavior and IQ; the strength of this effect across samples was estimated meta-analytically.
Eighty-seven boys from a longitudinal community study, 48 boys referred clinically for aggression, and 42 adult males diagnosed with attention-deficit/hyperactivity disorder.
IQ scores and observer ratings of externalizing behavior were taken from existing data sets.
Among individuals lacking the 7-repeat allele, externalizing behavior was negatively correlated with IQ (mean r = -0.43; P<.001). Among individuals having at least 1 copy of the 7-repeat allele, externalizing behavior and IQ were uncorrelated (mean r = 0.02; P = .45). The difference between these correlations was significant (z = -2.99; P<.01).
Allelic variation of the dopamine D4 receptor gene appears to be a genetic factor moderating the association between externalizing behavior and cognitive ability. This finding may help to elucidate the adaptive value of the 7-repeat allele.

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    • "Swanson et al. (2000), for example, conducted a study on children with ADHD and found that carriers of the 7r allele were at reduced risk for cognitive abnormalities (while still showing behavioral symptoms) compared to carriers of the 4r homozygous variant. Similarly, DeYoung et al. (2006) showed that cognitive ability was associated with externalizing behavior only for individuals who did not carry the 7r allele. Carriers of one or two copies of the 7r allele did not show this association. "
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