Summary

While methamphetamine use has long been associated with psychosis, this study provided evidence for a strong dose-dependent relationship between methamphetamine use and psychotic symptoms. A 5-fold increase in psychosis was observed during periods of use compared with periods of abstinence.

Design

• N=278 participants meeting DSM-IV criteria for methamphetamine dependence, and without history of schizophrenia or mania.
• Participants were 72% male, 78% unemployed, 89% Australian born, average age: 31.7 (SD=8.1)
• Structured interviews given at baseline, 3 months, 1 year, 3 years. Data collected on drug use, psychotic symptoms, health, and social functioning in the past month.
• Primary outcome: Psychotic symptoms defined as a score ≥4 on any Brief Psychiatric Rating Scale item for suspiciousness, unusual thought content, or hallucination in past month.
• Data on number of days of methamphetamine use in past month was collected, and confirmed with hair testing in a subsample of participants (false reporting in only 6% of cases).
• Setting: Sydney and Brisbane, Australia, from 2006-2010.
• Statistical analysis: Fixed-effects logistic regression model used to determine within-subject relationship between methamphetamine use and psychotic symptoms, in each of the four discreet 1-month time periods.

Results

• Participants were five times as likely to experience psychosis while using methamphetamines. Odds Ratio: 5.3 (95% CI 3.4-8.3, P<0.001)
• Increase in psychosis was dose-dependent. For those using methamphetamines (vs abstinence) ≥16 days per month, OR=11.2, compared with ≤15 days per month, OR=4.0.
• Using alcohol or cannabis ≥16 days per month further increased the likelihood of psychosis.
• Participants had used methamphetamines for an average of 13.1 years (SD=7.9), with 83% injecting it. Drug was used on a mean of 8 days during months of use.
• 60% of participants reported psychotic symptoms during at least one of their four months observed by the study. 71% of symptoms involved suspiciousness, 51% hallucinations, and 35% delusions or unusual thoughts. Most symptoms were moderate.

Reference

McKetin R, Lubman DI, Baker AL, Dawe S, Ali RL. Dose-Related Psychotic Symptoms in Chronic Methamphetamine Users. JAMA Psychiatry. 2013;70(3):319. doi:10.1001/jamapsychiatry.2013.283.