Serotonin Transporter Genotype (5HTTLPR) Moderates the Longitudinal Impact of Atypical Attachment on Externalizing Behavior.

OBJECTIVE To test whether genotype of the serotonin transporter-linked polymorphic region (5HTTLPR) and atypical attachment interact to predict externalizing psychopathology prospectively in a sample of children with a history of early institutional care. METHODS Caregiver report of externalizing behavior at 54 months was examined in 105 children initially reared in institutional care and enrolled in the Bucharest Early Intervention Project, a randomized controlled trial of high quality foster care. 5HTTLPR genotype, attachment status at 42 months of age (typical [secure, avoidant, or ambivalent] or atypical [disorganized-controlling, insecure-other]), and their interaction were examined as predictors of externalizing behavior at age 54 months. RESULTS 5HTTLPR genotype and atypical attachment at age 42 months interacted to predict externalizing behavior at age 54 months. Specifically, children with the s/s genotype with an atypical attachment had the highest externalizing scores. However, s/s children with a typical attachment demonstrated the lowest externalizing scores, even after controlling for intervention group status. There was no association between attachment status and externalizing behavior among children carrying at least 1 copy of the l allele. CONCLUSION These findings indicate that genetic variation in the serotonergic system moderates the association between atypical attachment status and externalizing in young children. Our findings suggest that children, as a result of genetic variability in the serotonergic system, demonstrate differential sensitivity to the attachment relationship.