Causal effect modeling with naturalistic rather than experimental data is challenging. In observational studies participants in different treatment conditions may also differ on pretreatment characteristics that influence outcomes. Propensity score methods can theoretically eliminate these confounds for all observed covariates, but accurate estimation of propensity scores is impeded by large numbers of covariates, uncertain functional forms for their associations with treatment selection, and other problems. This article demonstrates that boosting, a modern statistical technique, can overcome many of these obstacles. The authors illustrate this approach with a study of adolescent probationers in substance abuse treatment programs. Propensity score weights estimated using boosting eliminate most pretreatment group differences and substantially alter the apparent relative effects of adolescent substance abuse treatment.
This study examined 2 process variables, emotional engagement and habituation, and outcome of exposure therapy for posttraumatic stress disorder. Thirty-seven female assault victims received treatment that involved repeated imaginal reliving of their trauma, and rated their distress at 10-min intervals. The average distress levels during each of 6 exposure sessions were submitted to a cluster analysis. Three distinct groups of clients with different patterns of distress were found: high initial engagement and gradual habituation between sessions, high initial engagement without habituation, and moderate initial engagement without habituation. Clients with the 1st distress pattern improved more in treatment than the other clients. The results are discussed within the framework of emotional processing theory, emphasizing the crucial role of emotional engagement and habituation in exposure therapy.
This study examines the effectiveness of using vouchers to reinforce either the provision of urine samples testing negative for illicit drugs (UA group) or the completion of objective, individually defined, treatment-plan-related tasks (TP group). A third group was assigned to the clinic's standard treatment (STD group). Participants were randomly assigned to groups after a 6-week baseline-stabilization period. Urine specimens were collected thrice weekly throughout the study. In the UA condition, participants earned $5 (U.S. dollars) in vouchers for each drug-free urine submitted. In the TP condition, participants earned up to $15 in vouchers per week for demonstrating completion of treatment plan tasks assigned by their counselors. Contingencies were in effect for 12 weeks, after which all participants received the clinic's standard treatment. Urinalysis results indicate that the TP intervention was significantly more effective in reducing illicit drug use than either the UA or STD interventions. These effects were maintained with a trend toward continuing improvement for the TP groups even after contingencies were discontinued.
Whereas strong efficacy research has been conducted on novel treatment approaches for adolescent substance abusers, little is known about the effectiveness of the substance abuse treatment approaches most commonly available to youths, their families, and referring agencies. This report compares the 12-month outcomes of adolescent probationers (N = 449) who received either Phoenix Academy, a therapeutic community for adolescents that uses a treatment model that is widely implemented across the U.S., or an alternative probation disposition. Across many pretreatment risk factors for relapse and recidivism, groups were well matched after case-mix adjustment. Repeated measures analyses of substance use, psychological functioning, and crime outcomes collected 3, 6, and 12 months after the baseline interview demonstrated that Phoenix Academy treatment is associated with superior substance use and psychological functioning outcomes over the period of observation. As one of the most rigorous evaluations of the effectiveness of a traditional community-based adolescent drug treatment program, this study provides evidence that one such program is effective. Implications of this finding for the dissemination of efficacious novel treatment approaches are discussed.
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