PRODROMES AND PRECURSORS - EPIDEMIOLOGIC DATA FOR PRIMARY PREVENTION OF DISORDERS WITH SLOW ONSET

Objective: The concepts of prodrome and precursor are used to show how epidemiologic data on age at onset can be used in timing preventive i nterventions and selecting target populations. Method: Data concerning onset of DSM-III major depression and panic disorder were taken from the Epidemiologic Catchment Area Program. Cumulative distributions of ages at onset of diagnosis and onset of precursors are presented and t he concept of attributable risk is introduced. Attributable risk is th e maximum proportion of cases that would be Prevented if art intervent ion were 100% effective in eliminating a specific precursor. Results: Illustrative results for depression and panic are presented. Precursor s vary in the degree to which they predict onset of the full disorder; 2 or more weeks of sad mood in the year before full-blown depression is a better predictor (relative odds, 7.0) than weight loss or gain (r elative odds, 3.0). The formula for population attributable risk was a pplied to the precursor relative risks and prevalences to estimate the potential success of interventions for specific precursors in prevent ing the disorder. The precursor attributable risks indicate that sleep problems would identify 47% of the new cases of major depression occu rring in the following year, and the question ''Are you a nervous pers on?'' would identify 60% of persons with onset of panic disorder in th e following year. Conclusions: This conceptual framework links the ear ly natural history of disorders with the search for syndromes. Knowled ge of precursor prevalence and attributable risk, combined with other host characteristics and environmental risk factors, can be used in sc reening and prevention.