Abstract
Objective: Many adolescents engage in polydrug use; however, little is known about whether alcohol and other drug problems show similar posttreatment trajectories of change. We examined concurrent patterns of change for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, symptoms related to the use of alcohol, marijuana, and other drugs and identified predictors of the most common cross-drug patterns of change. Method: Adolescents (N=542) recruited from addictions treatment were assessed at baseline and at 1- and 3-year follow-up. Latent class mixture modeling identified trajectories for alcohol, marijuana, and other-drug symptoms. Latent class analysis identified cross-drug patterns of change and was used to examine conduct disorder and depression as predictors of cross-drug patterns of change. Results: For alcohol users, three improving groups (72%), stable-low (19%) and stable-high (6%) groups, and groups with increasing trajectories (3%) were identified. For marijuana users, an asymptomatic class (230/6), two improving classes (46%), stable-low (13%) and stable-high (13%) classes, and a class with an increasing trajectory (4%) were found. For users of other drugs, groups with asymptomatic (57%), improving (20%), increasing (12%), and stable-high (11%) trajectories were identified. Latent class analysis of cross-drug patterns of change identified three subtypes representing generally concordant cross-drug patterns of change and one subtype that involved stable-high marijuana problems, decreasing alcohol problems, and increasing other-drug problems. Conduct disorder was associated with greater persistence of substance problems. Conclusions: The majority of treated adolescents had similar cross-drug patterns of change for alcohol, marijuana, and other drugs; however, exceptions exist. Furthermore, adolescents with co-occurring psychopathology may benefit from continuing intervention, because they tend to report more persistent posttreatment substance-related problems.