Is our concept of schizophrenia influenced by Berkson's bias?
BACKGROUND
If both positive and negative dimensions of schizophrenia independently influence need for care, a higher estimate of the comorbidity between these dimensions is expected in clinical samples than would be the case if non-clinical cases were investigated (i.e. Berkson's bias). The present paper investigates whether positive and negative dimensions independently contribute to mental health care use in a general population sample.


METHODS
A prospective cohort study was conducted, in which 7076 individuals were interviewed with the Composite International Diagnostic Interview Schedule at baseline and 1 and 3 years later. Lifetime positive and negative psychotic experiences (PPE, NPE) were assessed at baseline. Mental health care use (MHC) was assessed at baseline, and prospectively 1 and 3 years later.


RESULTS
The rating of MHC was strongly associated with NPE and PPE, both retrospectively and prospectively and the effects of both variables remained strong and significant in the analyses with both variables included.


CONCLUSIONS
These results, therefore, suggest that the concept of schizophrenia, as a unitary entity with high comorbidity between positive and negative dimensions, is in part the result of Berkson's bias.
Maric
N
N
Dept. of Psychiatry & Neuropsychology, South Limburg Mental Health Research and TEACHING Network, EURON Maastricht University, 6200 MD Maastricht, The Netherlands.
Myin-Germeys
I
I
Delespaul
P
P
de Graaf
R
R
Vollebergh
W
W
Van Os
J
J
D000293:Adolescent; D000328:Adult; D015982:Bias; D015331:Cohort Studies; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008297:Male; D008605:Mental Health Services / Q000706:statistics & numerical data*; D008875:Middle Aged; D009426:Netherlands; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D011594:Psychometrics / Q000706:statistics & numerical data; D012559:Schizophrenia / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology*; D012565:Schizophrenic Psychology