Background: During these last years, many structured and standardized diagnostic interviews have been developed in order to identify psychiatric disorders in a standardized way. These tools enable a systematic investigation of these disorders according to international classifications. Their main drawback is to be long. To assess the care of depression, we used a shorter and more simple tool: the Mini International Neuropsychiatric Interview (MINI) to identify depressive subjects.
Method: The study was conducted in the Gazel cohort from the French National Electricity and Gas Company. A stratified sample of 2394 civil servants selected in order to over-represent depressive subjects was asked to answer to the MINI interview through a phone interview. An epidemiological and statistical analysis was performed to test the MINI internal validity: prevalence of depressive disorders using different threshold of diagnosis (number of symptoms required to identify someone as depressive), frequency of different symptoms, variability between investigators and potential biases.
Results: Respondents to the phone interview (1108 civil servants) had more often presented depression markers for the last 5 years. Prevalence of depressive episodes changed little when we varied the threshold of diagnosis and did not stress any threshold problem. The variability between investigators was important, but the estimation of prevalence remained stable when we excluded extreme rates of prevalence. The choice of a classification system affected the prevalence estimation. Using the Diagnostic and Statistical Manual of Mental Disorders (DSM IV) from the American Psychiatric Association, the prevalence of depressive episodes was lower and closer to the estimations shown in the literature than using the International Classification of Disease (ICD 10). Moreover, the stratification assigned very unbalanced weights to the stratification strata. By excluding depressive episodes observed in the stratum "control" (no depression "marker" from 1989 to 1994 in the database), the prevalence was very lower, whatever the classification was. Finally, factors which appeared linked to care of depression with the ICD definition remained the same when the DSM diagnosis definition was used, and relative risks were quite similar.
Conclusion: The MINI appears to be a short and simple tool, suited to the epidemiological studies. This analysis does not highlight any failure in the internal consistency of the MINI. The remaining question is what the MINI really measures, particularly comparing to a psychiatrist's diagnosis.