Genetics of depression: A social science perspective

Almost all genetic research on depression, until recent work with the Virginia Twin Register, has been based on 'non-neurotic' conditions seen in-patient settings. While these have provided firm evidence for genetic effects, they are not relevant for the bulk of depressive disorders. The importance of a comparative population approach for the latter is emphasized as an adjunct to genetically sensitive designs since the latter deal only with variance arising from individual variability within a population. This means that it is possible for population differences in rates of disorder to be essentially determined by parallel differences in psychosocial factors even on the conservative assumption that a genetic liability is present in every instance of the disorder. The perspective is particularly important where, as with depression, a clinically relevant condition can show large differences in rates between populations. Behavioural genetic concepts of heritability and shared environment are discussed in the light of the possibility that the bulk of depressive conditions ('neurotic' depression) have relatively little genetic influence and that early intrafamilial experience of neglect and abuse are of aetiological importance.