This study shows that in the Netherlands mental disorders are prevalent. In about a decade, no clear change in mental health status was found.

The psychiatric epidemiological population study NEMESIS-2 (Netherlands Mental Health Survey and Incidence Study-2) replicates and expands the first Netherlands Mental Health Survey and Incidence Study (NEMESIS-1) conducted from 1996 to 1999. The main objectives of the new study are to provide up-to-date figures on the prevalence, incidence, course and consequences of mental disorders, and to study trends in mental disorders and service use, with the use of a new sample. New topics not included in NEMESIS-1 were added, e.g. impulse-control disorders, and genetic correlates of mental disorders through gathering DNA from saliva samples. This paper gives an overview of the design of NEMESIS-2, especially of its recently completed first wave. NEMESIS-2 is a prospective study among Dutch-speaking subjects aged 18-64 years from the general Dutch population. Its baseline wave included 6646 subjects. Three waves are planned with three year-intervals between the waves. A multistage, stratified random sampling procedure was applied. The baseline wave of NEMESIS-2 was performed between November 2007 and July 2009. Face-to-face interviews were administered with the Composite International Diagnostic Interview (CIDI) 3.0. The response rate was 65.1%, and 76.4% of the respondents donated saliva. The sample was reasonably nationally representative, but younger subjects were somewhat underrepresented. In conclusion, we were able to build a comprehensive dataset of good quality, permitting several topics to be studied in the future.

No abstract

The extended psychosis phenotype, or the expression of nonclinical positive psychotic experiences, is already prevalent in adolescence and has a dose-response risk relationship with later psychotic disorder. In 2 large adolescent general population samples (n = 5422 and n = 2230), prevalence and structure of the extended psychosis phenotype was investigated. Positive psychotic experiences, broadly defined, were reported by the majority of adolescents. Exploratory analysis with Structural Equation Modelling (Exploratory Factor Analysis followed by Confirmatory Factor Analysis [CFA]) in sample 1 suggested that psychotic experiences were best represented by 5 underlying dimensions; CFA in sample 2 provided a replication of this model. Dimensions were labeled Hallucinations, Delusions, Paranoia, Grandiosity, and Paranormal beliefs. Prevalences differed strongly, Hallucinations having the lowest and Paranoia having the highest rates. Girls reported more experiences on all dimensions, except Grandiosity, and from age 12 to 16 years rates increased. Hallucinations, Delusions, and Paranoia, but not Grandiosity and Paranormal beliefs, were associated with distress and general measures of psychopathology. Thus, only some of the dimensions of the extended psychosis phenotype in young people may represent a continuum with more severe psychopathology and predict later psychiatric disorder.

The associations between cannabis use and the first incidence of depression and bipolar disorder, which remained significant after adjustment for strong confounders, warrant research into the underlying mechanisms.