Associations between anhedonia and marijuana use escalation across mid-adolescence.

BACKGROUND AND AIMS: Anhedonia-a transdiagnostic psychopathological trait indicative of inability to experience pleasure-could lead to and result from adolescent marijuana use, yet this notion has not been tested. This study aimed to estimate the association of: (1) anhedonia at age 14 with rate of change in marijuana use over an 18-month follow-up, and (2) marijuana use at age 14 with rate of change in anhedonia over follow-up. Secondary aims were to test whether gender, baseline marijuana use history and peer marijuana use moderated these associations.

DESIGN: Observational longitudinal cohort repeated-measures design, with baseline (age 14 years), 6-month, 12-month and 18-month follow-up assessments.

SETTINGS: Ten public high schools in Los Angeles, CA, USA, 2013-15.

PARTICIPANTS: Students [n = 3394; 53.5% female, mean (standard deviation) age at baseline = 14.1 (0.42)].

MEASUREMENTS: Self-report level of anhedonia on the Snaith-Hamilton Pleasure Scale and frequency of marijuana use in the past 30 days.

FINDINGS: Parallel process latent growth curve models adjusting for confounders showed that baseline anhedonia level was associated positively with the rate of increase in marijuana use frequency across follow-ups [β, 95% confidence interval (CI) = 0.115 (0.022, 0.252), P = 0.03]. Baseline marijuana use frequency was not related significantly to the rate of change in anhedonia across follow-ups [β, 95% CI = -0.015 (-0.350, 0.321), P = 0.93]. The association of baseline anhedonia with faster marijuana use escalation was amplified among adolescents with (versus without) friends who used marijuana at baseline [β, 95% CI = 0.179 (0.043, 0.334) versus 0.064 (-0.071, 0.187), interaction P = 0.04], but did not differ by gender or baseline ever marijuana use.

CONCLUSIONS: In mid-adolescence, anhedonia is associated with subsequent marijuana use escalation, but marijuana use escalation does not appear to be associated with subsequent anhedonia.