This article reports the initial results of a prospective study on the prevalence of psychiatric disorders in the Dutch population aged 18-64. The objectives and the design of the study are described elsewhere in this issue. A total of 7076 people were interviewed in person in 1996. The presence of the following disorders was determined by means of the CIDI: mood disorders, anxiety disorders, eating disorders, schizophrenia and other non-affective psychoses, and substance use disorders. Psychiatric disorders were found to be quite common. Some 41.2% of the adult population under 65 had experienced at least one DSM-III-R disorder in their lifetime, among them 23.3% within the preceding year. No gender differences were found in overall morbidity. Depression, anxiety, and alcohol abuse and dependence were most prevalent, and there was a high degree of comorbidity between them. The prevalence rate encountered for schizophrenia was lower (0.4% lifetime) than generally presumed. A comparison with findings from other countries is made. Relevant determinants of psychiatric morbidity were analysed.

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This article discusses the effects of sociodemographics and the presence of psychiatric disorders diagnosed in the 12 months before the first interview by using the Diagnostic and Statistical Manual of Mental Disorders: DSM-III-R, third edition, revised, on three types of attrition (failure to locate, refusal to participate, morbidity/mortality) in the second wave (1997-1998) of the Netherlands Mental Health Survey and Incidence Study, a longitudinal, general population survey of psychopathology among 7,076 subjects aged 18-64 years. Compared with those reinterviewed successfully, persons not located at the 1-year follow-up (n = 219) were more often younger, poorly educated, urban, not cohabiting with a steady partner, and born outside the Netherlands. Refusers (n = 923) had a lower educational level. Morbidity/mortality (n = 72) was associated with higher age, lower educational level, not being employed, and somatic disorders. After adjustment for sociodemographics, none of the disorders was positively associated with refusal. Failure to locate was linked to agoraphobia, alcohol abuse, and the categories of mood, substance use, and eating disorders. Morbidity/mortality was linked to dysthymia, agoraphobia, simple phobia, obsessive-compulsive disorder, and the category of anxiety disorders. Overall attrition was only slightly higher among respondents with one or more disorders (odds ratio = 1.20, 95% confidence interval: 1.04, 1.38). Thus, psychopathology has only weak-to-moderate effects on attrition and is mainly related to failure to locate and morbidity/mortality but not to refusal.

The article describes the objectives and design of a prospective study of the prevalence, incidence and course of psychiatric disorders in a representative sample of non-institutionalized Dutch adults. A total of 7146 men and women aged 18-64, contacted through a multistage sample of municipalities and households, were interviewed at home in 1996. The primary diagnostic instrument was the CIDI, which determines the lifetime occurrence of DSM-III-R disorders. The disorders included were: mood disorders, anxiety disorders, eating disorders, schizophrenia and other non-affective psychotic disorders, and dependence and abuse of psychoactive substances. Follow-up measurements in the same sample were scheduled at 12 and 36 months. The net response to the first measurement was 69.7%. Poststratification weightings were applied for gender, age, marital status and degree of urbanization. Limitations and advantages of the study design are discussed. Findings are reported elsewhere in this issue.

Mental health care providers should be aware that the extent and the type of disability may vary with the different types of disorders and among different groups within the population. Since recovery from functional limitations may not be complete or may take more time than the remission of the psychiatric symptomatology, non-psychiatric follow-up care is needed. The high number of lost work days is relevant from an economic perspective. There is a need for illness-specific disability assessment instruments.