Age of onset in affective disorder: its correlation with hereditary and psychosocial factors

Affective disorders probably have a multifactorial aetiology, both biological and psychosocial factors may be of importance at onset as well as at relapses. The aim of the study was to investigate how the age of onset of bipolar and unipolar disorder relates to family history of affective disorder, early parental separation and life events. A second purpose of this study was to analyze the importance of life events preceding the first and subsequent episodes of affective disorder.

The case records of 282 patients (161 females/121 males; mean age 56) were investigated. They all had a DSM-IV based diagnosis of either bipolar I/II (67%) or unipolar (33%) disorder. Variables, such as family history, early parental loss and life events according to Paykel life events scale, were examined.

We found a significantly lower age of onset in bipolar patients with a family history of affective disorder (28.9 vs. 33.9 years). Bipolar patients with preceding life events had a higher age of onset (33.1 vs. 28.3 years). Moreover, bipolar patients with heredity, had less life events at onset. For the bipolar, as well as the unipolar group, life stressors more frequently preceded the first episode of affective disorder than the subsequent episodes.

The major limitation of this study is the retrospective approach, with e.g. difficulties to decide whether a life event plays a role in aetiology of affective disorder or is its consequence.

Bipolar patients with high constitutional vulnerability have an earlier age of onset and need less stress factors to become ill. Better knowledge about the stress- and the vulnerability-factors in affective disorder might contribute to development of individually tailored therapeutic strategies in future.