Factors that influence trajectories of change in frequency of substance use and quality of life among adolescents receiving a brief intervention.

This study aimed to identify factors influencing trajectories of change in two outcome domains, frequency of substance use and quality of life (QOL), among adolescents receiving a brief evidence-based intervention. Participants were 106 adolescents, aged 13 to 21 years, who met criteria for a substance use disorder. The adolescents received a five-session intervention and completed four assessments over 12 months. Based upon a theoretical and empirical review, five putative predictors were tested: gender, age, severity of conduct disorder, severity of depression, and peer substance involvement. Results of a parallel-process latent growth curve model indicated that higher peer substance involvement and conduct severity predicted higher frequency of use at baseline, whereas higher peer substance involvement and depression severity predicted poorer QOL at baseline. Counter to predictions, higher depression severity predicted greater improvements in QOL following substance use treatment. The implications of baseline risk factors on adolescents' response to intervention are discussed.