A Genetic Study of Affective Disorder

It is well known that when affective illness has its onset in later life a family history of this illness is significantly less common than in cases where the onset is early. Thus, Kay (1959) compared cases in this respect before and after 60 years of age; the morbidity risk was 10–12·7 per cent for relatives of the early onset group and only 3·5–5·7 per cent in relatives of those falling ill for the first time after 60. Similarly, Hopkinson (1964), taking the age of 50 to divide his probands, found a significantly lower risk for affective illness in relatives of the older-onset probands.