In this randomized clinical trial of the efficacy of a computer-assisted CBT program for reducing drug use, participants using the CBT4CBT program submitted significantly fewer drug-positive urines specimens and tended to have longer periods of abstinence during treatment compared with standard TAU at a community based clinic. This is to our knowledge the first randomized clinical trial evaluating computer-assisted treatment for substance use disorders that reports on biologically-verified drug use outcomes. Thus, the study both adds to the existing positive literature on computer-assisted delivery of CBT for depression and anxiety disorders by extending it to a new and highly challenging population, but also provides strong evidence for the efficacy of computer-assisted training via use of data from urine toxicology screens, rather than self- or therapist report, both of which may be subject to bias. The CBT4CBT program was viewed by participants as highly engaging, was associated with promising outcomes, and potentially addresses a critical issue related to the availability of CBT in clinical practice.
Similarly, this trial is consistent with multiple trials suggesting practice of CBT skills outside of sessions via completion of homework assignments may be an important active ingredient of outcome CBT (34
) in that there was a significant positive relationship between number of CBT4CBT homework assignments completed and substance use outcomes. That is, indicators of treatment involvement was strongly related to outcome in the CBT4CBT condition, while in the TAU condition outcome was more strongly related to baseline severity of substance use than level of treatment engagement. Given the link between use of the program and outcome, more frequent access to and use of the CBT4CBT program (e.g., via the internet), should be evaluated as a strategy to enhance the potential benefits of this approach.
Strengths of this trial included randomization of a comparatively large and diverse group of participants in a community clinic, comparable levels of retention and data availability in both conditions, and reliance on independent, biological indicators of outcome. While not addressed in this study, the high level of control over the delivery of specific modules or treatment components (such as homework) in computer-assisted training may permit more refined study of the specific mediators of CBT via future clinical trials where these elements are systematically manipulated with greater precision than is typically possible in clinician-delivered therapies.
This study had several limitations as well. First, it should be noted that the study did not address whether computer assisted delivery of training was comparable or superior to clinician-delivered CBT, nor did it control for the additional time the participants spent working with the computer program in addition to the TAU received. Moreover, use of a TAU comparison condition which was not constrained or controlled had the typical disadvantages of this type of comparison (49
), including variability in content and duration. On the other hand, it did constitute an active treatment comparison (50
) and therefore provided a rigorous control for evaluating any added benefit conferred by CBT4CBT. Second, in common with most trials involving substance users, attrition was an issue, as approximately 65% of those who initiated their protocol treatment completed it. On the other hand, data availability was comparable for both conditions and the retention rates are comparatively high given the unselected nature of the study population. Moreover, our extensive efforts to reach and collect data from those who dropped out of treatment (52
) provided complete data for over 80% of the treatment exposed sample for the full 56 day study period. Third, it should be noted that the analyses evaluating the relationships between baseline substance use severity, treatment involvement, and outcome; are correlational and causality cannot be inferred.
Finally, because CBT has been demonstrated to be effective across several substance use disorders we decided to evaluate CBT4CBT with a heterogeneous sample of outpatients who used multiple substances concurrently. While this provided stronger evidence for the generalizability of the CBT4CBT program, it produced insufficient sample sizes for analyzing different subgroups of patients. In this regard, it should also be noted that our significant urine outcomes are complicated by the fact that some substances are detectable in urine for longer periods (marijuana) than others (cocaine). On the other hand, detecting a significant difference under these circumstances and in a heterogeneous community-based sample provided comparatively strong support for this promising new model. These results should be replicated before CBT4CBT is advocated for broader use in the substance abuse treatment system, and we are currently conducting a larger trial with a more homogeneous cocaine-dependent methadone-maintained sample.