Lifetime patterns of depressive symptoms in the community and among primary care attenders: an application of grade of membership analysis.

The objective of this study was to describe empirical and natural lifetime patterns of depressive and anxiety symptoms reported by community respondents and primary care attenders. The Grade of Membership model was used to analyze data collected from 716 subjects between 18 and 64 years of age with a lifetime diagnosis of DIS/DSM-III-R Major Depressive Episode. Symptoms of depression, mania, and anxiety (GAD, panic attack, and phobias) were processed. Six prototype categories (pure types) provided the best description of the structure of symptoms included in the analysis. Type I: bipolar depression with marked suicidal behaviour, comorbidity and early onset. Type II: non-melancholic-somatisation depression with late onset. Type III: non-melancholic, non-severe bipolar depression with male preponderance. Type IV: depression secondary to anxiety with marked female preponderance. Type V: melancholic depression with suicide ideation. Type VI: melancholic depression with panic attacks and female preponderance. The results support the heterogeneity of the longitudinal symptom pattern of depression and the existence of two time-trend types of comorbid anxiety disorders.