Could cognitive deficits help distinguish methamphetamine-induced psychosis from a psychotic disorder with substance abuse?

Abstract

Dissociating a primary psychotic disorder (PPD) with concurrent substance use from substance-induced psychosis (SID) can be a difficult task. This study explored the possibility of distinguishing subgroups using cognitive functioning in order to potentially help diagnose individuals with a PPD co-occurring with substance-use and a methamphetamine (MA) induced psychosis. The hypothesis stipulates that individuals with a PPD should present with different cognitive deficits compared to individuals with SID. The study used the data collected as part of a longitudinal study (the MAPS project) that took place in Vancouver BC, Canada. One hundred and seventy-two individuals presenting with psychosis and MA abuse were recruited. Substance use, symptoms severity and cognitive deficits were assessed. A cluster analyses revealed two profiles: individuals in Cluster 1 had a poorer performance on the Gambling task net score (M = −28.1) and on the Hopkins Verbal Learning Test – Revised (HVLT-R; M = 63) % of retention score compared to those in Cluster 2. Individuals in Cluster 1 also had more negative symptoms, t = 2.29, p < 0.05 and were more likely to have had a psychiatric diagnosis, X ²(3) = 16.26, p < 0.001. Results suggest that cognitive predictors might help identify PPD that co-occur with MA abuse.

Keywords:

• dual-disorder
• schizophrenia
• methamphetamine-induced psychosis
• cognition

Acknowledgements

This research was supported by two Canadian Institute of Health Research (CIHR) grants, as well as by the Provincial Health Services Authorities of British Columbia. The authors would specifically like to thank the participants who took part in this project, as well as the research assistants, clinicians and the MARC members who helped along the way.