Age at onset of affective disorders in Italian and Swedish patients.

Variability of age at onset in affective disorder is a complex event where several variables play a role, resulting in a detectable observed distribution which can be viewed as related to the structural mechanism of the disease. To confirm previous results on factors affecting the distribution of onset in affective disorders, we studied its distribution pattern in two different populations, Italian and Swedish, with an analytic approach that does not require specifications of any a priori hypothesis. The findings in this study, however, tend to confirm the biological nature of the age of onset phenomenon and to exclude cultural determinants. On the other hand, it does not exclude that other factors, not considered in this study, may be operating. This result is very important under the hypothesis of a genetic ethiopathogenesis of affective disorders, and some of its implications are discussed.