The European journal of general practice vol:10 issue:4 pages:162-5, 168
BACKGROUND: Large and undeclared differences exist between incidence and prevalence rates of depression in general practice based morbidity registries, and in registries based on questionnaires of questionnaire-based interviews. We tried to identify possible explanations for these differences. METHOD: Literature-based discussions were held among a multidisciplinary group of clinicians and researchers. FINDINGS: Selection bias and imperfections in the diagnostic capabilities of each of the systems may play a role, but they are insufficient explanations for the differences that were identified. Questionnaires provide factual information on a patient's situation. Frequently no information is available on the intensity or consistency of the symptoms and on the personal growth or coping strategies that were developed by the patient. GPs may register depressive complaints as part of other psychological problems to which the depression is related. Their diagnostic strategy is part of a process to identify those who can benefit from specific interventions. In general practice, depression is a diagnosis that tends to emerge progressively. Depression can be considered as a way of coping with events. DSM-based questionnaires provide information that is more related to a latent characteristic of a personality, rather than a temporal, inappropriate expression of this characteristic, as identified in a clinical diagnosis. INTERPRETATION: Conceptual differences and different objectives when diagnosing, more than selection bias or diagnostic imperfections, tend to be responsible for the identified differences in occurrence rates of depression.