Psychiatric Times 
July 2005
Vol. XXII
Issue 8
In an attempt to reframe the long-standing debate over the either-or impact of genetics versus environment on emotional makeup, a panel titled "Genes-Environment Interactions: Developmental and Psychotherapeutic Implications" convened at the American Psychoanalytic Association's Winter 2005 Meeting in New York City.
Glen O. Gabbard, M.D., Brown Foundation chair of psychoanalysis and professor of psychiatry at the Baylor College of Medicine in Houston, presented data on the gene-environment interaction in antisocial and borderline personality disorders, showing that DNA is both inherited and environmentally modifiable. Gabbard told Psychiatric Times that there is today, in the field of psychiatry, a simplistic thinking that wants everything reduced to the genome.
"Most people do not like complexity, so there's a seductiveness about genetic reductionism," he said. "But genes alone do not determine personality, and we have good data now showing that it is a matter of genes interacting with the environment in the expression of those genes, and the environment making actual changes in that expression."
At the meeting, Gabbard described a long-term, follow-up study of 1,037 children in Dunedin, New Zealand--a birth cohort assessed every two years up to age 26 (Caspi et al., 2002). Measures included degree of maltreatment, monoamine oxidase A (MAOA) gene activity and antisocial behavior. Results showed that males with low MAOA activity who were maltreated in childhood had elevated antisocial scores, whereas males with high MAOA activity did not have the elevated scores even when they had experienced maltreatment. Overall, 85% of the males with both the low MAOA activity genotype and severe maltreatment became antisocial.
"The authors concluded that a functional polymorphism in the MAOA gene moderates the impact of childhood maltreatment on development of antisocial behavior. The point here, against reductionism, is that neither the low-activity gene alone nor the environmental maltreatment alone is enough to create antisocial behavior," explained Gabbard.
Those findings were replicated in a study of 514 male twins (ages 8 to 17), which showed that low MAOA activity increased risk for conduct disorder only in the presence of an adverse childhood environment (Foley et al., 2004). "Once again, the combination had to be present," Gabbard said.
