A systematic review of risk factors for methamphetamine-associated psychosis

Objective: Chronic methamphetamine use is commonly associated with the development of psychotic symptoms. The predictors and correlates of methamphetamine-associated psychosis are poorly understood. We sought to systematically review factors associated with psychotic symptoms in adults using illicit amphetamine or methamphetamine. Methods: A systematic literature search was performed on MEDLINE (OVID), PsycINFO and EMBASE databases from inception to 8 December 2016. The search strategy combined three concept areas: methamphetamine or amphetamine, psychosis and risk factors. Included studies needed to compare adults using illicit methamphetamine or amphetamine, using a validated measure of psychosis, on a range of risk factors. Of 402 identified articles, we removed 45 duplicates, 320 articles based on abstract/title and 17 ineligible full-text articles, leaving 20 included studies that were conducted in 13 populations. Two co-authors independently extracted the following data from each study: country, setting and design; participant demographic and clinical details; sample size; measure/s used and measures of association between psychosis outcomes and risk factors. Individual study quality was assessed using a modified Newcastle-Ottawa Scale, and strength of evidence was assessed using GRADE criteria. Results: Frequency of methamphetamine use and severity of methamphetamine dependence were consistently found to be associated with psychosis, and sociodemographic factors were not. There was inconsistent evidence available for all other risk factors. Individual study quality was low–moderate for the majority of studies. Heterogeneity in study outcomes precluded quantitative synthesis of outcomes across studies. Conclusion: The most consistent correlates of psychotic symptoms were increased frequency of methamphetamine use and dependence on methamphetamine. The findings of this review highlight the need for targeted assessment and treatment of methamphetamine use in individuals presenting with psychosis.