Heritability of major depression similar in twin, full/half-full siblings
Monozygotic and dizygotic twin pairs and full/half-siblings reared together and apart show similar heritability of major depression, according to a recent study. In addition, heritability is greater in women than in men, with the two sexes sharing most but not all genetic risk factors.
The heritability of major depression in men and women was estimated at 0.41 (95 percent CI, 0.21–0.49) and 0.49 (0.31–0.56) in the twin design, respectively. In the independent full/half-sibling design, estimates were 0.36 (0.31–0.38) and 0.51 (0.51–0.53), respectively. The best estimate of the association in genetic effects across sexes was 0.89 (0.87–0.91).
Evidence of modest shared environmental effects (0.02–0.05) was also seen in the findings. Of the eight indices of genetic risk examined, seven predicted the risk for major depression in relatives, with stronger effects in those more closely related. The strongest indices were as follows: early age at onset, recurrence, comorbid anxiety disorder and measures of clinical severity.
“In affected individuals, genetic risk for major depression could be meaningfully assessed from commonly available clinical indices,” the investigators said.
In this study, all treated cases of major depression in Sweden recorded in inpatients, specialist and primary care registries were examined. The aetiologic role of genetic and environmental factors from monozygotic and dizygotic twin pairs and full/half-siblings reared together and apart (n=1,718,863 pairs) was estimated using OpenMx. Finally, the investigators examined eight indices of genetic risk in 875,010 proband-relative pairs.