Higher
heritability of depression in women than in
men
The
heritability of major depression has been
estimated to be in the range of 35%-40%.
However, the impact of sex on the transmission
of major depression remained uncertain because
its detection requires large samples. A recent
powerful study designed to detect sex effects on
major depression found differences in the
genetic risk factors for major depression in men
and women. This large study of lifetime major
depression in twins also sought to determine the
stability of estimates of the heritability of
major depression across historical cohorts.
Data collection was performed with a
computer-assisted telephone interview, using the
simplified Composite International Diagnostic
Interview Short Form (CIDI-SF) to assess
lifetime prevalence of major depression, and the
analyses were based on 42,161 twins, including
15,493 complete pairs. The statistical analysis
used the software package Mx to evaluate twin
models.
The heritability of liability to major
depression was greater in women (42%) than in
men (29%) and the genetic risk factors for major
depression were correlated, but not identical,
between the sexes. No differences in the role of
genetic and environmental risk factors in the
etiology of lifetime major depression were found
in three cohorts, which together spanned the
years from 1900 to 1958.
The results of the heritability of major
depression were similar to those of previous
studies. They also showed the existence of genes
that have different impacts on the risk for
major depression in men and women. Genes might
alter the risk for depression in women in
response to the variable hormonal environment of
the menstrual cycle and pregnancy, but not in
men because they do not have the hormonal
fluctuations that occur in women. Research on
genetic vulnerability to depression should be
done separately in women and men. Kendler
KS, Gatz M, Gardner CO, Pedersen NL. A Swedish
national twin study of lifetime major
depression. Am J Psychiatry 2006,
163:109-114.