Major depression prevalence is very high, but the syndrome is a poor proxy for community populations' clinical treatment needs.

OBJECTIVES: Some basic questions about the epidemiology of major depression (MD) remain open to debate and interpretation. Prevalence is a case in point. There have been claims that prevalence has been both over- and underestimated. This review is an attempt to reconcile this apparent contradiction.
METHOD: A literature search was carried out using MEDLINE. Articles were screened for relevance in 2 stages and bibliographies were examined to identify additional relevant publications.
RESULTS: The claim that prevalence has been overestimated appears to hinge on a concern that current diagnostic criteria fail to adequately differentiate between pathological and nonpathological mood disturbances. These arguments pertain to the validity of diagnostic criteria rather than to the prevalence of the syndrome that the criteria define. Conversely, the claim that prevalence has been underestimated is based on studies providing evidence of recall bias. If DSM-IV criteria are accepted as a diagnostic definition, MD prevalence is considerably higher than usually cited figures. However, the same literature indicates that the spectrum of severity is much broader than is usually acknowledged. The DSM-IV criteria appear to be a poor proxy for treatment need in community populations.
CONCLUSIONS: Increasing evidence suggests that MD is very common but also that DSM-IV and ICD-10 definitions capture such a broad spectrum of morbidity that they should not be regarded as de facto indicators of need, at least not in community populations.