Does Contingency Management Enhance the Effects of Cognitive-behavioral Therapy on Cocaine Use?

Cognitive-behavioral therapy (CBT) and contingency management (CM; i.e., providing rewards for negative toxicology screens) are among the most empirically supported psychosocial interventions for substance use disorder, and for cocaine use disorders more specifically.

Questions remain about whether the interventions would be effective in treatment seekers outside the U.S. and whether a combination of these theoretically-consistent frameworks can enhance treatment outcomes.

Additional rewards for negative urine toxicology screens, for example, could bolster motivation to remain engaged in treatment and to use the cognitive behavioral therapy (CBT) skills learned between therapy groups.

Authors of this study addressed these questions by comparing a combination of cognitive-behavioral therapy and contingency management to cognitive-behavioral therapy alone (CBT/CM vs. CBT) via randomized controlled trial in 60 cocaine dependent adults (29 CBT/CM vs. 31 CBT) in an outpatient hospital setting in Basel, Switzerland. Participants were 80% male, 70% Swiss, and 35 years old on average. Regarding co-occurring disorders, 80% met criteria for another substance use disorder (SUD), 46% for a non-SUD Axis I disorder (e.g., major depression) and 23% for a personality disorder.

The study followed participants during 24 weeks of treatment and again 6 months after treatment. The cognitive behavioral therapy (CBT) intervention was based on an existing, evidence-based model for individuals, with 18 sessions delivered by a trained psychologist or psychiatrist. All participants provided urine toxicology screens twice per week during the first 12 weeks of treatment, and weekly during the latter 12 weeks. Missed toxicology screens were counted as positive. For those in CBT/CM, participants with a negative toxicology screen for the cocaine metabolite drew from a bowl of 500 chips; of those, 250 resulted in no prize, 219 a prize valued at $2, thirty a $20 prize, and one a $500 prize. Drugs other than cocaine were not part of the CM. Primary outcomes were treatment engagement (i.e., retention), number of cocaine abstinent weeks, and the proportion of cocaine free urine samples. The study also examined other relevant clinical outcomes such as addiction severity and depression.

The authors found that about 60% of the sample completed treatment with no differences between the groups. Across the entire sample, participants’ negative urinalyses increased from 25% at baseline to 48% at treatment end, and frequency of cocaine use significantly decreased overall from baseline to 6-month follow-up.

While authors found several differences between the treatment conditions, none were statistically significant, likely due to the study’s small sample; for example 55% of CBT/CM’s urine samples were negative during treatment, compared with about 42% of CBT participants. Post-hoc analyses showed that on several occasions during treatment, CBT/CM had a significantly greater proportion of patients with negative urinalyses (e.g., week 21).

Participants’ reported improvements on all secondary outcomes during treatment though, again, groups were not different; follow-up (i.e., post-treatment) results of secondary outcomes were not presented. Regarding study cost, rewards for CBT/CM participants cost $576 on average.

IN CONTEXT

A recent meta-analysis showed that contingency management (CM) generally produces a clinically meaningful improvement in substance use (Cohen’s d = .5), that decays relatively quickly (within 6 months) over time once the CM is removed.

This study adds to body of contingency management (CM) literature by including individuals outside of the U.S. and testing CM’s ability to enhance CBT. In keeping with U.S. studies, when an advantage was present, it typically favored the combined CM/CBT intervention.

Given the generally robust positive effects found for CM while it is in place, a challenge for the treatment and recovery field is finding a way to extend CM paradigms over the long-term and to discover how long exactly contingency management (CM) paradigms need to be in place in order for other lifestyle and/or brain changes to occur that can support sustained remission and recovery once the contingency is removed.

LIMITATIONS

• Small sample size limited the overall impact of the study. Not only did it reduce authors’ ability to find group differences (i.e., statistical power), but also called into question the finding of similar group characteristics at baseline as less certain. For example, although 55% of the CBT group compared to 38% of the CBT/CM group met criteria for a non-SUD Axis I disorder, groups were considered statistically similar and therefore “equivalent”.
• Co-occurring psychiatric disorders can reduce SUD treatment benefit, suggesting the CBT group may have been at a disadvantage to start.
• Another important feature is that urinalyses only focused on cocaine, though 80% of the sample met criteria for at least one other SUD.

A follow-up study with a larger sample, and that examined drugs in addition to cocaine (e.g., opiates) would help clarify these issues.

BOTTOM LINE

CITATIONS

Petitjean, S. A., Dürsteler-MacFarland, K. M., Krokar, M. C., Strasser, J., Mueller, S. E., Degen, B., … & Farronato, N. S. (2014). A randomized, controlled trial of combined cognitive-behavioral therapy plus prize-based contingency management for cocaine dependence. Drug and alcohol dependence, 145, 94-100.