Reliability and relationship of various ages of onset criteria for major affective disorder.

This paper presents data on six different clinical definitions (indices) of age of onset for major affective disorders. The inter-rater reliability for each index and the relationships among these indices are discussed. Age of onset for impairment with affective symptoms was found to be a reliable and useful index of early onset. It discriminated between unipolar depressed subjects and both bipolar I and bipolar II subjects.