The temporal association between frequency of methamphetamine use, depression, and anxiety in a community-recruited cohort of methamphetamine smokers
Background: Elevated rates of anxiety and depression are known to occur in people who use methamphetamine. Much of the existing literature is cross-sectional in nature, and involves participants recruited from drug treatment services or criminal justice settings. There is a particular paucity in literature examining associations between methamphetamine use and anxiety. The present study examines longitudinal associations between frequency of methamphetamine use, anxiety, and depression in community-recruited methamphetamine smokers.
Methods: Data were derived from baseline and 6-monthly follow-up surveys conducted between August 2016 until March 2020. More than 800 participants from metropolitan and non-metropolitan areas of Victoria, Australia, recruited for the prospective 'VMAX' study via snowball and respondent driven sampling. Outcomes of interest, anxiety and depression 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. Generalised linear mixed models were used to examine association between frequency of methamphetamine use and PHQ-9 and GAD-7 scores.
Results: More than 60% of the VMAX cohort were experiencing either depression and anxiety at baseline, and depression and anxiety were highly correlated to each other. Depression and anxiety were both found to be significantly related to frequency of methamphetamine use; increasing frequency of methamphetamine use was associated with higher odds of experiencing moderate to severe depression or anxiety over the course of the study.
Conclusion: Longitudinal associations of depression and anxiety with frequent methamphetamine use emphasize the need for treatment services to provide integrated models of care, whereby needs related to depression, anxiety, and methamphetamine use are met. Further work is needed to examine longitudinal trends and predictors of health service use for the purpose of mental health, particularly for those experiencing moderate to severe depression or anxiety.