Vol. 12, No. 4, 2006 Page 6
In 2002, researchers reported that abused children have far less risk of "going wrong" in adulthood if they possess a high-activity variant of a particular gene. A new study by the same authors supports and extends this finding.
In their initial paper (see related article, Crime Times, 2002, Vol. 8, No. 4, Page 1), Avshalom Caspi and colleagues reported that males with a high-activity variant of a gene affecting levels of the enzyme monoamine oxidase A (MAOA) rarely developed antisocial behavior, even if severely abused as children. In contrast, 85% of severely abused males with a low-activity variant of the gene developed some form of antisocial behavior. Terrie Moffitt, a coauthor of the paper, concluded, "The combination of the low-activity MAOA genotype and maltreatment predicts antisocial behaviors as well as high cholesterol predicts heart disease."
In the new study, the same research team (this time headed by Julia Kim-Cohen) evaluated 975 seven-year-old boys. They report, "Among children who were exposed to physical maltreatment, boys with the low- activity MAOA allele had mental health problem scores that were half a standard deviation higher than boys with the high-activity allele." The low-activity gene appears to increase maltreated children's risk for ADHD- related symptoms as well for as a broader range of problems that, the researchers say, "together signal the beginning of a maladaptive trajectory toward the development of antisocial behavior." Because this study involved young children rather than adults, the researchers say it indicates that low MAOA activity can influence responses to stressful events early in life.
"Eventually," they say, "such evidence can inform not only what treatments might help prevent psychopathology in physically maltreated children but also when such intervention might be most successful."
Interestingly, non-abused children with the high-activity variant of the MAOA gene had slightly elevated levels of overall mental health problems, antisocial behavior, and attention deficits or hyperactivity compared to non-abused boys with the low-activity gene variant—a finding consistent with several other studies. This suggests that high MAOA activity affects behavior in varying ways, depending on environmental factors.
Noting that attempts to replicate their initial findings have had mixed results, the researchers next performed a meta-analysis— that is, an examination of combined data from several related studies. This method can detect trends that are not obvious in individual studies. "Pooling estimates from five studies," they say, "we found that the association between early familial adversity and mental health was significantly stronger in the low-activity MAOA vs. the high-activity MAOA groups."
MAOA is an enzyme that metabolizes the neurotransmitters serotonin, dopamine, and norepinephrine. Because these chemicals are involved in multiple brain functions involving reactions to stress, the researchers say that MAOA function "is likely to be one of myriad factors involved in the development of biological sensitivity to stress and the social context."
"MAOA, maltreatment, and gene-environment interaction predicting children's mental health: new evidence and a meta-analysis," J. Kim-Cohen, A. Caspi, A. Taylor, B. Williams, R. Newcombe, I. W. Craig and T.E. Moffitt, Molecular Psychiatry, Vol. 11, 2006, 903-13. Address: J. Kim-Cohen, Department of Psychology, Yale University, P.O. Box 208205, New Haven, CT 06520, julia.kim-cohen@yale.edu.