Posted by Shell on October 24, 2000, at 22:51:24
I recently came across a study of the heritability of depression. A large group (over 2,500) of identical twins were asked questions (interviewed separately) designed to discover whether they had experienced any symptoms of psychiatric disorders, including depression. The researchers used three definitions of depression – “people who had been depressed for at least two weeks at least once during their life” (24% of the men, 31% of the women), “people whose depressive episodes had hampered their ability to perform daily tasks or who had sought treatment for depression” (16% of the men, 22% of the women), and people who had had at least “six symptoms of depression in an episode that persisted for at least four weeks” (3% of the men, 9% of the women).
Based on the whether or not depression had occurred in both or only one twin of a pair, the researchers estimated the heritability of depression for males to range from 1% to 24%. For females, they estimated heritability to range from 36% to 44%. The heritability figures were similar no matter which of the three definitions were used. They concluded that the common impression that “severe” depression is more “genetic” and that “mild” depression is more “environmental” does not seem to be the case.
I have read that heritability is the proportion of variation of a trait that can be attributed to genetic factors as opposed to environmental ones. Can anyone give me a good idea of what that really means? The authors did note that, “So in men, depression was only modestly familial, which means that individual environmental factors play a larger role in the development of male depression." I would assume that the converse would then be true; in females genetic factors play a larger role.
Does this also mean that the daughters of a depressed person are more likely to inherit a tendency towards depression than are the sons? Does anyone know if there are statistics that say (for example), “If a person has one parent who has experienced depression, he/she has an X% chance of experiencing depression him/herself and if both parents have been depressed, then he/she has a Y% chance of experiencing depression”?
Any thoughts would be appreciated,
Shell
poster:Shell
thread:1590
URL: http://www.dr-bob.org/babble/social/20001011/msgs/1590.html