Case definition and case identification in psychiatric epidemiology: review and assessment

Psychiatric epidemiology has advanced considerably since early studies of hospital populations. The direction of this advance has been away from the study of populations of hospital psychiatric patients towards the study of psychiatric disorder in general practice and the community as a whole. Just as the populations under study have different defining characteristics, so have the individuals who comprise them. Psychosis becomes less and less common at greater distances from the hospital patient, and in the community the epidemiologist is faced with large numbers of respondents who present with fewer, minor and non-specific symptoms. In this review, we present evidence to indicate that concepts of case definition and case identification are insufficiently advanced so far, and are still rooted in ideas derived from hospital psychiatry. Foremost among these is an exclusive preoccupation with diagnosis and symptoms. We suggest that this may be inadequate for the study of non-psychotic disturbance in the community, and discuss other models of case definition, encompassing personality and social functioning as well as psychiatric symptomatology.