Incest: what do we really know about it?

The literature on incest is reviewed. Current knowledge rests on a very insecure scientific basis and has been mainly derived from small, highly selected clinical series. Recently, some important epidemiological studies of general populations have been reported, but the results of prevalence are inconsistent. Overall, however, it appears that incest, when defined in terms of sexual intercourse, occurs in less than 1% of the population, but other forms of intrafamilial sexual activity may affect 10% of females before they are 16 years of age. Some children are more at risk than others. Because information has generally been derived from court or treatment samples, we are unclear about the long-term effects of incest experiences but, overall, the impression is that incest has markedly adverse effects, especially if it is accompanied by violence and threats and is directed, as it usually is, at the young pre-pubescent child.