Lifetime risk of depression.

Over the past decade, major epidemiological studies have been conducted to determine the prevalence of depressive syndromes, primarily major depression or dysthymia. The highest prevalences occur in younger cohorts (18-29 years); considerably lower prevalences are found in older individuals (45 years and above), with the lowest in those aged 65 and older. Several studies have confirmed an increase in the cumulative lifetime estimates of major depression in successively younger birth cohorts during this century. At the same time, questions have been raised about the low prevalence of depression in the elderly, including the role of confounding factors (e.g. differential morbidity and response-biased memory). Standardised diagnostic assessment procedures may be insufficiently adapted for use in the elderly. It has also been recognised that a substantial number of elderly individuals suffer from clinically relevant symptoms of depression but do not meet the criteria for major depression. Future research will be required to elucidate fully the apparently changing rates of depression.