The Stockholm non-affective psychoses study (snaps): the importance of including out-patient data in incidence studies.
OBJECTIVE
To estimate the incidence rate of schizophrenia and non-affective psychoses from registers, to highlight the importance of including data from out-patient care, and to assess the proportion of persons treated in out-patient care only.


METHODS
Data from out-patient and in-patient psychiatric care in Stockholm and information from several national registers constitute 'The Stockholm Non-Affective Psychoses Study' (SNAPS). Incidence rates based on SNAPS data were calculated and compared to in-patient care incidence rates.


RESULTS
The incidence rate was 72/100 000 for non-affective psychoses (age group 18-44) and 28/100 000 for schizophrenia (age group 18-34) in the SNAPS. This was higher compared to in-patient based incidence rates (42 and 13/100 000 respectively). The proportion of individuals with psychosis treated in out-patient care only was 25%.


CONCLUSIONS
There are substantial differences in the incidence rates of non-affective psychoses and schizophrenia depending on the availability of data. Not including out-patient care will underestimate the incidence rates.
Jörgensen
L
L
Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden. lena.jorgensen@ki.se <lena.jorgensen@ki.se>
Ahlbom
A
A
Allebeck
P
P
Dalman
C
C
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000553:Ambulatory Care / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011618:Psychotic Disorders / Q000175:diagnosis / Q000453:epidemiology*; D012042:Registries; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology*; D015983:Selection Bias; D013548:Sweden; D014505:Urban Population / Q000706:statistics & numerical data*; D055815:Young Adult