Heritability
of major depression Is higher in women than in men
Newswise — Virginia
Commonwealth University researchers have found that genes
contribute more strongly to the risk of depression in women
than in men, and that there may be some genetic factors that
are operating uniquely in one sex and not in the other.
In the January issue of
the American Journal of Psychiatry, researchers
reported that heritability of depression is higher in women
– approximately 42 percent -- than in men, where it is
approximately 29 percent.
“Our work, together with
colleagues at the Karolinska Institute in Sweden, represents
the largest epidemiological study of depression in twins
done to date. In addition, it broadly replicates what has
been shown by our earlier work using the Virginia Twin
Registry. In particular, we have shown that depression is a
moderately heritable disorder, suggesting that genetic
factors are important, but by no means overwhelming,” said
Kenneth S. Kendler, M.D., a professor of psychiatry and
human genetics in VCU’s School of Medicine and lead author
on the study.
The research team employed
twin study models to evaluate lifetime major depression of
approximately 42,000 twins, including 15,000 complete pairs
from the Swedish National Twin Registry.
According to Kendler, the
sex-effects are of two kinds – quantitative and qualitative.
He said that quantitative sex-effects examine whether
heritability is different in males compared with females,
and if the overall importance of genetic factors differs
between the sexes; whereas qualitative sex-effects examine
whether the same genes are playing a role in males and
females.
For example, Kendler said
there may be genes that alter the risk for depression in a
woman’s response to cyclic sex hormones, particularly in the
postpartum period. Such genes would impact a woman’s risk
for major depression, but would not be active in men because
men lack the relevant hormonal milieu.
The Virginia Twin Registry
is now part of the VCU Mid-Atlantic Twin Registry (MATR),
which contains a population-based record of twins from
Virginia, North Carolina and South Carolina.
This work was supported in
part by grants from the National Institutes of Health
(MH-49492), the Swedish Scientific Council and the Swedish
Department of Higher Education.
Kendler collaborated with
Charles O. Gardener, Ph.D., from VCU; and Margaret Gatz,
Ph.D., and Nancy L. Pedersen, Ph.D., who are affiliated with
the University of Southern California and the Karolinska
Institute in Stockholm, Sweden.