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June 20, 2011

Acting out after experiencing discrimination - what do genes have to do with it?

Brody, G.H., Beach, S.R.H., Chen, Y-F., Obasi, E., Philibert, R.A., Kogan, S.M., & Simons, R.L. (2011). Perceived discrimination, serotonin transporter linked polymorphic region status, and the development of conduct problems. Development and Psychopathology, 23, 617-627.

These authors were interested in changes in conduct problems during later adolescence. Conduct problems are antisocial behaviours such as aggression, destruction of property, lying and theft. These kinds of behaviours predict criminal behaviour in adult life. This study aimed to examine the contribution of young people’s experiences of discrimination in the development of conduct problems among African American adolescents. Furthermore, the study aimed to examine whether certain genetic differences among young people could make the effects of perceived discrimination on the development of conduct problems greater or lesser (i.e. whether genetic differences could reduce the likelihood that young people would develop conduct problems after they had experienced discrimination).

The genetic difference these authors investigated was the serotonin transporter gene 5-HTT.This gene differs between people who carry short or long versions of the allele 5-HTTLPR. Short versions of the allele tend to be seen in people who pay more attention to threatening things in their environment, so people with short alleles were expected to display higher levels of conduct problems in response to perceived discrimination. This genetic risk/resilience factor also seems to be more important for boys than girls.

Participants in this study were 454 African American young people living in rural Georgia, USA. These young people took part when aged 15, 16, and 17 years old. Perceived discrimination and conduct problems were self-reported by the participants, while the DNA data were collected using saliva samples.

Results supported the authors’ expectations. For boys with the short allele, levels of perceived discrimination were associated with conduct problems – when there was very little perceived discrimination this group actually had lower conduct problems than the long allele group, but when there were high levels of discrimination the short allele group showed higher levels of conduct problems. Among the long allele group the level of discrimination did not influence level of conduct problems.

The genetic variation of interest (short vs. long allele 5-HTTLPR) here seems to act as both a protective factor and risk factor – when little or no discrimination is present those with the short allele are actually better off than those with only long alleles. However, when there is high levels of discrimination present, those with the short alleles are in danger of increasing conduct problems. The authors note that others have suggested that the gene variation investigated here relates to how sensitive people are to their environment, and that while short alleles place them at risk of problems when they are in a difficult environment the sensitivity to context also means that they are more likely to take advantage of positive environments than people with only long alleles (also see Jay Belsky’s work in this regard).

Regarding the gender differences, the article suggests that the generally low levels of conduct problems among girls may account for this difference here, especially since aggression and acting out is viewed as a gender appropriate way for boys to deal with stress.

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