Despite the need for marijuana dependence treatment in the United States, research on how to intervene effectively with this problem has been conducted only recently. This section describes the results of controlled trials conducted in the last decade to evaluate interventions for adults who are marijuana dependent. Special consideration is given to MTP, which is the largest study ever conducted of people who smoke marijuana.

Controlled Studies

The first controlled trial of marijuana dependence treatment (Stephens et al. 1994b) compared the effects of 10 sessions of cognitive behavioral therapy (CBT) with 10 sessions of group discussion. The participants were 212 people who had used marijuana daily or almost daily for an average of 10 years. Both counseling approaches were modestly effective in helping a significant portion of participants achieve either abstinence or improvement. Contrary to predictions, the CBT approach was no more effective than social support with adults who were marijuana dependent.

Higher levels of pretreatment marijuana use predicted higher use levels following treatment. Lower socioeconomic status predicted more problems associated with marijuana use after treatment. Finally, individuals who before treatment indicated greater self-efficacy for avoiding marijuana use had more successful posttreatment outcomes (Stephens et al. 1993b).

In a related study (Stephens et al. 2000), a brief, 2-session individual treatment was compared with 14 sessions of CBT skills training. In this study a delayed treatment control group was included to determine the extent to which self-initiated change occurs in this population in the absence of formal treatment. This group was placed on a waiting list and asked to come back in 4 months. The sample consisted of 291 adults who smoked marijuana daily. The 14 CBT skills training sessions were delivered in a group setting over a 4-month period. This treatment emphasized the learning of coping strategies to deal with situations presenting high risk of relapse. It also provided additional time to build group cohesion and support. The second active treatment consisted of two motivational enhancement therapy (MET) counseling sessions delivered as individual therapy over a 1-month period.

An important element involved giving participants normative information so they could compare their marijuana use with that of the general population and that of other people seeking treatment for marijuana dependence. The counselor reviewed with each participant a written personal feedback report generated from questions asked during a comprehensive intake assessment. The counselor used the client’s reaction to the personal feedback report to promote discussion and bolster the client’s motivation to abstain from marijuana use. The information also was used to reinforce clients’ confidence in their ability to end marijuana use and to offer support in goalsetting strategies for behavior change. One month later, the second session reviewed efforts to abstain and the coping skills used in the interim period. In both treatment conditions, participants had the option of involving a support person.

The results showed that both active treatments produced substantial reductions in marijuana use relative to the delayed treatment control condition. Following treatment, there were no differences between the two active treatments in abstinence rates, days of marijuana use, severity of problems, or number of dependence symptoms. Similarly, at the 16-month assessment, 29 percent of group counseling participants and 28 percent of individual counseling participants reported having been abstinent for the past 90 days. The results of this study suggest that minimal interventions consisting of as little as two sessions may be more cost-effective than lengthier treatments.

In another study (Budney et al. 2000), 60 adults who were marijuana dependent were randomly assigned to one of three 14-week treatments: (1) MET, (2) MET plus coping skills training, or (3) MET plus coping skills training and voucher-based incentives. In the last condition, participants whose abstinence from marijuana and other drugs was documented by urinalysis received vouchers that were exchangeable for retail items (e.g., movie passes, sports equipment,educational classes). The value of each voucher increased with each successive instance of confirmed abstinence. Conversely, the occurrence of a cannabinoid-positive urine specimen (or the failure to submit a sample) led to a reduction of each voucher’s value to its initial level. The results showed that participants in the voucher-based incentive condition were more likely to achieve continuous abstinence from marijuana during treatment than were participants in the other two conditions. Moreover, a greater percentage of participants in the voucher-based condition (35%) were abstinent at the end of treatment than was the case in theskills training (10%) or MET (5%) conditions.

The results of these studies indicate that a substantial proportion of adults who were marijuana dependent and who sought treatment have been aided in either stopping or decreasing their marijuana use. However, it is also apparent that not all of those treated achieved the initial goal of sustained abstinence from marijuana. Given the evidence of marijuana’s dependence potential and adverse health and behavioral consequences, continuing development and testing of marijuana dependence interventions are clearly warranted.