The Biology of Late-Life Depression

Current evidence suggests that depression is clearly not a single entity but a syndrome characterized by a broad spectrum of symptom type and severity, and chronicity of illness. Depression is one of the most frequent psychiatric disorders in the geriatric population, though figures of prevalence have ranged from 5 to 44% depending on the method of identification (Blazer & Williams, 1980). Interestingly, data from the ECA study revealed that the lifetime prevalence of depression was four times lower in persons aged 65 years or older than in individuals aged 25 to 44 at the time of the ECA (Myers, Weissman, Tischer, et al., 1984). However, Berkman et al. (1986) obtained data to support the view that the presence of significant depressive symptoms, but not major depression, are more frequent among the elderly. In that study only 1–2% of the subjects fulfilled DSM III criteria for major depression but more than 10% had depressive symptoms. It is unclear at the present time whether those depressive symptoms are largely due to psychosocial factors, biological factors, or a combination of the two. Several investigators have suggested that depression in late life is a distinct entity from depression in early life. Genetic predisposition seems to play only a modest role in the aethiopathogenesis of geriatric depression when compared with a younger age group (Hopkinson, 1964; Mendlewicz, 1976).