Anxiety and depression among a community-recruited cohort of people who use methamphetamine: A longitudinal analysis.

Aims: This study (1) estimated changes in anxiety and depression throughout 3 years in a community-recruited cohort who use methamphetamine and (2) modelled whether these changes were associated with patterns of methamphetamine use or other time-varying or fixed covariates.

Design, setting and participants: We used a longitudinal analysis using data derived from surveys conducted between August 2016 and March 2020, set in metropolitan and rural locations in Victoria, Australia. Participants comprised a total of 849 adults with regular methamphetamine use history at baseline, recruited for the prospective VMAX study via snowball and respondent-driven sampling.

Measurements: Anxiety and depression symptoms were measured using the Generalized Anxiety Disorder (GAD)-7 and the Patient Health Questionnaire (PHQ)-9 instruments. Frequency of methamphetamine use was measured by self-reported number of days per week participants used any form of methamphetamine in the past month.

Findings: Changes in anxiety and depression symptom scores were associated with change in route of administration from non-injecting to injecting [adjusted coefficient (adj. coeff.) = 1.44, 95% confidence intervals (CI) = 0.39, 2.48, adj. coeff. = 1.49, 95% CI = 0.39, 2.58], change in severity of dependence for methamphetamine (adj. coeff. = 0.29, 95% CI = 0.21, 0.37, adj. coeff. = 0.34, 95% CI = 0.26, 0.42), starting treatment for drugs other than methamphetamine (adj. coeff. = -2.21, 95% CI = -3.70, -0.73, adj. coeff. = -2.09, 95% CI = -3.60, -0.58) and other covariates.

Conclusions: Among regular methamphetamine users in Australia, changes in anxiety or depression scores are associated with changes in route of administration, dependence severity and starting treatment for other drugs, but do not appear to be associated with frequency of methamphetamine use.