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The risk of substance-induced psychosis converting to schizophrenia varies with substance used and patient age

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Question: What is the risk of substance-induced psychosis (SIP) converting into schizophrenia spectrum disorder?

Population: All 18 478 individuals (81% men, mean age 43.7 years) in Finland with a first hospital admission for SIP between 1987 and 2003. Individuals were identified using the Finnish Hospital Discharge Register, and were followed until first occurrence of a schizophrenia spectrum disorder, death or the end of December 2003, whichever occurred first.

Setting: Finland; January 1987–December 2003.

Prognostic factors: A discharge diagnosis of SIP between 1987 and 2003 (based on DSM-III-R codes prior to 1995 and ICD-10 codes thereafter). The substance associated with the SIP admission was recorded where available and adjusted for in analyses. Additional factors considered as covariates were age, sex and duration of initial hospitalisation for SIP.

Outcomes: Conversion to a discharge diagnosis of a schizophrenia spectrum disorder during follow-up to December 2003 (DSM-III-R codes for diagnoses prior to 1995 and ICD-10 codes thereafter). Conversion rate was calculated by dividing the number of cases by the …

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  • Sources of funding: The Finnish Psychiatric Association, the Finnish Society of Addiction Medicine and the Academy of Finland.


  • Competing interests None.