Depressed mood states and their inter-relationship with clinical depression.

A study was conducted to contrast depressed mood states in those positive and negative for lifetime depressive syndromes. A non-clinical cohort of 156 subjects was assessed on four occasions over 15 years, with 35% having had a major depression and 22% a minor depression at the most recent assessment. At 5-yearly reviews, estimates were obtained of episode frequency, duration and symptom patterns during depressed mood states. Such characteristics were then contrasted across the three groups of those who had experienced major depression, those who had suffered minor depression and lifetime non-cases. Depressive states were affirmed by at least 96% of subjects at each assessment, with the mean number of episodes per assessment year ranging from 8.6 to 21.2. Those who had experienced a lifetime episode of major depression differed from the two contrast groups (i.e. those with minor depression: non-cases) in having more episodes and more features during episodes. By contrast, there was a gradient across the three groups for two other examined features, with those having major depression being more likely than those with minor depression, who in turn were more likely than the non-cases to have longer episodes and a greater number of symptoms. The greater frequency, severity and duration of depressed mood states in those who met lifetime criteria for a major depressive episode suggest that their threshold to onset and persistence of a variety of depressive experiences is lowered, so supporting a general vulnerability hypothesis.