Abstract
AIMS: To estimate cannabis use disorder (CUD) trajectory classes from ages 14 to 30 years and compare classes on clinical characteristics, risk factors and psychosocial outcomes. DESIGN: Four waves (T1-T4) of data from an epidemiological study of psychopathology among a regionally representative sample. Trajectory classes described risk for CUD as a function of age. The number of classes was determined by model fit. SETTING: Participants were selected randomly from nine high schools in western Oregon, USA. PARTICIPANTS: The sample included 816 participants [age at T1 mean = 16.6, standard deviation (SD) = 1.2; 44% male; 8% non-white]. MEASUREMENTS: Participants completed diagnostic interviews, Child Trauma Questionnaire, Social Adjustment Scale and items adapted from the Wisconsin Manual for Assessing Psychotic-Like Experiences. FINDINGS: There were three CUD trajectory classes (Lo-Mendell-Rubin likelihood ratio test < 0.001): (1) persistent increasing risk; (2) maturing out, with increasing risk then decreasing risk; and (3) stable low risk. The persistent increasing class had later initial CUD onsets (η(2) = 0.16, P < 0.001) and greater cumulative CUD durations (η(2) = 0.26, P < 0.001). Male sex [odds ratio (OR) = 2.57, P = 0.018], externalizing disorders between ages 24 and 30 years (OR = 2.64, P < 0.001) and psychotic experiences during early adulthood (Cohen's d = 0.44, P = 0.016) discriminated between the persistent increasing and the maturing-out classes. CONCLUSIONS: Evidence suggests three distinguishable types of trajectory for development of cannabis use disorder starting in early teens: (1) persistent increasing risk; (2) maturing out, with increasing risk then decreasing risk; and (3) stable low risk.