Treated incidence and baseline characteristics of substance induced psychosis in a Norwegian catchment area.

BACKGROUND: Substance misuse is a well-recognized co-morbidity to psychosis and has been linked to poor prognostic outcomes in patients. Researchers have yet to investigate the difference in rates and characteristics between first-episode Substance Induced Psychosis (SIP) and primary psychosis. We aimed at comparing patients with SIP to primary psychosis patients with or without substance misuse at baseline.

METHODS: Thirty SIP patients, 45 primary psychosis patients with substance misuse (PS) and 66 primary psychosis patients without substance misuse (PNS) in a well-defined Norwegian catchment area were included from 2007-2011. Assessments included symptom levels (PANSS), diagnostic interviews (SCID), premorbid function scale (PAS) and global functioning (GAF f/s).

RESULTS: Treated incidence for SIP was found to be 6.5/100 000 persons per year, 9.7/100 000 persons per year for PS and 24.1/100 000 persons per year for PNS (15-65 yrs). Patients who had substance misuse (PS and SIP) were more likely to be male. Duration of Untreated Psychosis (DUP) was significantly shorter in the SIP group (5.0 wks., p = 0.003) and these had more positive symptoms on the PANSS (p = 0.049). SIP patients also did poorer on early youth academic levels on the PAS.

CONCLUSIONS: Yearly treated incidence of SIP is 6.5/100 000 persons per year in a Norwegian catchment area. SIP patients have short DUPs, are more likely to be male, have more positive symptoms at baseline and poorer premorbid academic scores in early adolescence. Follow-up will evaluate stability of diagnosis and characteristics.