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TWO-PRONGED STUDY AGAIN LINKS GENE TO ABUSED CHILDREN'S RISK OF BECOMING ANTISOCIAL ADULTS
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."
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"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.
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