The lifetime prevalence of mental disorders: estimation, uses and limitations

The age-specific lifetime prevalence rate of a disease is the proportion of persons surviving to a given age who have experienced the disease at any time during their lives. This measure of morbidity has been used to report findings in many of the epidemiological surveys of mental disorders of the last 30 years. This paper presents a life-table method for estimating age-specific lifetime prevalence rates from incidence and mortality data. The method is applied to Monroe County, New York, case register data on the incidence of schizophrenia. Using this method, we estimate that at least 3% of the White population surviving to age 55 have experienced an episode of schizophrenia at some time during their lives. The difficulties of producing valid estimates of lifetime prevalence and the difficulties in interpreting differences reported in such rates make this morbidity measure of secondary importance to incidence and point-prevalence data.