Treatment that combines vouchers and cognitive-behavioral therapy (CBT) may be more effective in keeping marijuana abusers abstinent in the longer term than vouchers-only and CBT-only programs. In a study by Dr. Alan Budney and colleagues at the University of Vermont, vouchers alone generated the longest periods of abstinence during 14 weeks of treatment, while vouchers and CBT in combination yielded superior abstinence during a 12-month posttreatment period.
"This is our second study demonstrating that an abstinence-based voucher program can increase positive outcomes for folks seeking treatment for marijuana dependence," says Dr. Budney, who is now at the University of Arkansas for Medical Sciences. "It provides evidence that vouchers used as adjuncts to traditional behavioral therapy can improve outcomes."
The current study extended the earlier one by including post-treatment assessments. Vouchers provided a strong incentive for abstinence during treatment, as they did in the earlier study, but the effect of vouchers alone did not hold up as well as the combined treatment once the program ended. The higher posttreatment abstinence rates for the combined treatment relative to the vouchers-only treatment suggest that the behavioral therapy helped to maintain the effect of the vouchers, Dr. Budney says. He attributes this maintenance effect to the coping skills and motivational training provided by the CBT.
For the study, 90 adults (69 men, 21 women) seeking treatment for marijuana dependence at a university-based outpatient clinic in Burlington, Vermont, were randomly assigned to treatment with vouchers (30), CBT (30), or both (30). Most were smoking marijuana daily and presenting themselves for treatment for the first time; their average length of marijuana abuse was 14 years. Each time a participant in the vouchers-only or combination treatment submitted a marijuana negative urine sample, he or she received a voucher worth $1.50; a second consecutive negative sample earned $3.00, a third $4.50, and so on. In addition, each consecutive pair of negative samples netted a bonus voucher worth $10. A full 14-week run of weekly drug-free samples would net vouchers worth $570, which were redeemable for retail goods or services.
The CBT included 50-minute weekly sessions involving motivational counseling, drug refusal, and coping skills. To encourage cooperation with the urine screens and help equalize retention and treatment contact across the groups, researchers paid the CBT-only participants $5 in vouchers each time they showed up for a screen, regardless of their test results. Complete adherence to the sessions and screens would earn $140 over the 14-week period.
During treatment, vouchers-only patients produced the most marijuana-negative urine specimens (55 percent versus 43 percent for combined treatment and 32 percent for CBT only), weeks of continuous abstinence (mean 6.9 versus 5.3 for combined treatment and 3.5 for CBT only), and continuous abstinences lasting 6 or more weeks (50 percent versus 40 percent for combined treatment and 17 percent for CBT only). In addition to duration of abstinence, researchers measured days of self-reported marijuana abuse, changes in marijuana-related problems, and psychosocial outcomes. Participants in all three groups showed similar improvements in these areas at the end of treatment (see chart).
Combined Treatment Benefits
At the end of treatment and at each of four quarterly followups, patients who received the combined treatment had the highest abstinence prevalence, averaging 38 percent over the 12 months, compared with 23 percent for vouchers only and 20 percent for CBT only. The combined treatment group also had the highest rate of continuous abstinence throughout treatment and followup, 37 percent, compared with 30 percent for CBT and 27 percent for vouchers. On average, patients who received the combination treatment used marijuana 13 days out of 30 during followup, compared with 18 days among patients who received the single treatments.
|Primary abstinence outcomes||CBT||CBT+V||V|
|Mean weeks of continuous abstinencea||3.5||5.3||6.9|
|% of participants who achieved 6 or more weeks of continuous abstinencea,b||17.0||40.0||50.0|
|% marijuana-negative urine specimens||32.0||43.0||55.0|
|Number of days marijuana used during prior monthc||CBT||CBT+V||V|
|End of Treatment||8.6||9.7||11.3|
|Number of times marijuana used per dayc||CBT||CBT+V||V|
|End of Treatmenta||1.6||2.7||2.6|
|Marijuana Problem Scalec||CBT||CBT+V||V|
|End of Treatment||5.1||3.6||4.1|
Data for all analyses were based on all participants (n = 30 per treatment condition).
Mean data reflect means adjusted for abstinence prior to treatment.
a CBT vs. V, comparison p < .05
b CBT+V vs. CBT, comparison p < .05
c Significant main effect for time, p < .01
"The findings of this study show that vouchers are effective in producing initial abstinence during treatment," says Ms. Debra Grossman of NIDA's Division of Clinical Neuroscience and Behavioral Research. "The addition of cognitivebehavioral therapy did not enhance initial abstinence, but helped maintain abstinence and produced better long-term outcomes. These findings are consistent with other studies." In two previous studies with cocaine abusers, vouchers alone performed as well as vouchers plus CBT during treatment. One of the studies indicated that CBT augmented the effects of the vouchers during the posttreatment period.
Dr. Budney says his team set the value of the vouchers arbitrarily, with the aim of keeping costs down; he believes bigger payoffs would produce better outcomes. The escalating values for consecutive negative urine samples progressively strengthened the incentive for participants to avoid lapses; each time a participant submitted a positive sample or missed a screening, the reward for the next negative sample reverted to the original $1.50 voucher. Dr. Budney suggests that future studies might cut costs by incorporating behavioral therapy only at key points in the treatment, rather than weekly throughout. In the researchers' experience, such a point often comes in the fourth to sixth week of abstinence, when patients may start to lose motivation and become vulnerable to relapse.
Fewer than half of the participants in Dr. Budney's study had positive outcomes, indicating that more effective treatments are needed for marijuana dependence. "Despite the promising findings, the majority of patients are not being sufficiently helped, and thus we need continued research focused on maximizing the outcome," Ms. Grossman notes. "Marijuana is the most commonly used illegal drug in the United States, yet among the least studied, and treatment based on abstinence-based vouchers has been found to be effective for other drugs of abuse."
Budney, A.J., et al. Clinical trial of abstinence-based vouchers and cognitive-behavioral therapy for cannabis dependence. Journal of Consulting and Clinical Psychology 74(2):307-316, 2006. [Abstract]