Family-based association test of the 5HTTLPR and aggressive behavior in a general population sample of children

Background. A promoter polymorphism in the serotonin transporter (5HTTLPR) has functional effects on an important/physiologic process involved in serotonin (5HT) signaling. Despite the fact that variation in the 5HT system has long been implicated in the etiology of aggressive behaviours, only a few association-based studies with mixed results have been reported. Methods: We conducted family-based tests of association in a sample of 366 families from which 1187 genotypes of the 5HTTLPR were generated using polymerase chain reaction. Ratings of aggressive behavior were obtained from parents and teachers longitudinally using the Child Behavior Checklist (CBCL) and Teacher Report Form (TRF), instruments widely used in behavioral and psychiatric genetics. Results: Within-family tests suggest an association between the s-allele of the 5HTTLPR and higher aggressive behavior in iniddle childhood. The strongest association was at age 9 and for an aggregate measure of teacher-rated aggressive behavior Conclusions: This is the first report of an association analysis of the 5HTTLPR in a general population, sample of school-age children. The results provide some support for the hypothesis that the functional effects of the 5HTTLPR s-allete are associated with higher levels of aggressive behavior in middle childhood.