Self-disparagement as feature and forerunner of depression: findings from the Stirling County Study.

Sleep disturbance has attracted considerable attention as an early indicator of depression. However, three epidemiologic investigations have shown psychological symptoms, such as self-disparagement, to be stronger predictors. This report examines the depressive symptoms commonly assessed in modern epidemiologic surveys and estimates the generalizability of this information using data from the Stirling County Study, a long-term epidemiologic investigation of psychiatric disorders. The Diagnostic Interview Schedule (DIS) was used to gather information about depression, defined as major depressive episode (MDE) and/or dysthymic disorder (DysD). A sample of 1,396 adults representing Stirling County in 1992 served to assess the prevalence of the different types of depressive symptoms and to investigate the associations between symptoms and lifetime diagnoses of MDE/DysD. A cohort of 489 follow-up subjects who were interviewed twice in the early part of the 1990s was used to examine the associations between baseline symptoms and subsequent incidence of MDE/DysD. Both "symptom groups" (such as appetite or psychomotor disturbances) and "individual symptoms" (such as weight gain or restlessness) were investigated. About one third of the representative sample had experienced the diagnostically required symptoms of "sadness" or "loss of pleasure," but many lacked sufficient other symptomatology to be diagnosed as depressed. Several of the symptom groups bore a different relationship to diagnosis than did the individual symptoms. Among the latter, "feeling worthless" and "having trouble concentrating" exhibited the strongest associations to diagnosis in the representative sample. The symptoms of "wanting to die" and "feeling worthless" were the most predictive of future depression in the twice-interviewed cohort. Thus, this study supports evidence from other epidemiologic studies that psychological symptoms are important in the prodromal phase of depression. Sleep disturbance, especially insomnia, cannot be ignored since it is a prominent manifestation of depression but it appears not to have as high specificity as some of the other symptoms. An exclusive focus on the symptom groups, as used to count symptoms according to diagnostic criteria, may obscure useful information about associations between individual symptoms and diagnosis. Feelings of personal inadequacy deserve particular attention in the population at large because they are strongly associated with lifetime diagnoses and forecast the incidence of depression when people are followed over time.