Three-Month Polysubstance Use Patterns Among People Enrolled in Outpatient Treatment for Methamphetamine Use.

Background: Polysubstance use is common among people who use methamphetamine. This prospective study examined the three-month polysubstance use profiles among people enrolled in outpatient treatment for methamphetamine use and associated substance use, mental health, and treatment correlates.

Method: The present study used routinely collected client-reported outcome measures data from N = 1,507 clients enrolled in outpatient treatment who reported methamphetamine as their primary drug of concern (Mean age = 34.48; SD = 8.68; 56% male). Past-month substance use was assessed at baseline, one-, and three-months.

Findings: Repeated measures latent class analyses revealed four classes: (1) high and decreasing methamphetamine + stable moderate alcohol + stable high cannabis and daily tobacco (n = 474, 31.45%); (2) stable high methamphetamine + stable high alcohol and daily tobacco (n = 346, 22.96%); (3) low and decreasing methamphetamine + stable moderate daily tobacco (n = 322, 21.37%); (4) stable high methamphetamine + stable moderate daily tobacco (n = 365, 24.22%). Probability of using substances other than methamphetamine remained relatively stable for each class across time. Classes 1 and 4 had greatest severity of methamphetamine involvement at baseline and three-months. Class 1 had greater odds of experiencing moderate-to-severe depression and anxiety, and PTSD and psychosis, compared to class 3.

Conclusion: Individuals enrolled in outpatient treatment who report methamphetamine as their primary drug of concern report distinct substance use patterns, although daily tobacco use was mostly ubiquitous. Polysubstance use was widespread, with 79% of participants having moderate-to-high probability of polysubstance use at all timepoints. Clients with the most severe polysubstance use had the highest rates of co-occurring psychopathology.