The present study provides limited and preliminary but controlled evidence that an ACT approach may be at least somewhat helpful in the treatment of marijuana dependence. Objectively confirmed self-reports of marijuana use showed that all participants were no longer using marijuana at posttreatment. At 3-month follow-up, 1 participant was still at posttreatment levels and the other 2 were using at somewhat reduced levels compared to baseline. Two other participants dropped out of treatment in the early stages. However, high attrition is a common problem in marijuana abuse treatment research (e.g., Budney et al., 2000
Marijuana dependence is an enormous problem, and effective treatment procedures are needed (McRae et al., 2003
). Treatment options include relapse prevention (Stephens et al., 1994
), motivational enhancement procedures (Budney et al., 2000
; Stephens et al., 2002
), cognitive behavior therapy and coping skills training (Budney et al.; Copeland et al., 2001
; Stephens et al., 2002
), and voucher-based motivational incentives (Budney et al.). Unfortunately, all these approaches suffer from limited effectiveness in both the short and long term as well as other limitations including high attrition (McRae et al.). Even though the findings from this study were no more notable than previous attempts at treating marijuana use, they are important because the treatment takes a theoretically and procedurally different approach. Specifically, ACT does not attempt to reduce or control private events that are associated with substance use, but rather helps to create a verbal context in which urges to use and thoughts about using can be experienced and not acted on. The ultimate effectiveness of approaches such as ACT is still unclear, but it provides preliminary evidence suggesting the need for additional research. Nonetheless, the application of this approach to marijuana dependence presented methodological complications.
First, the use of a multiple baseline design with a clinical intervention presents some unique challenges. In most behavioral interventions the independent variable can be administered in one session, and results are apparent relatively rapidly. In a clinical intervention the independent variable is gradually administered over a longer period of time, which resulted in lengthy baselines for the 2nd and 3rd participants in this study. This creates an ethical dilemma that must be balanced with the need for good experimental control, namely how much of a change must be seen in the previous participant before the independent variable can begin to be presented to the following participant? In this investigation, the treatment was initiated for Participants 2 and 3 as soon as a clinically significant change was seen for the preceding participant. This resulted in initiating treatment for Participants 2 and 3 prior to the preceding participant's marijuana use reaching near zero, but after significant changes determined by slope and means occurred. This resulted in a different, but experimentally sound, multiple baseline than is usually seen in single-subject research.
Second, it is unclear what is the best dependent variable for self-monitoring of marijuana use. In this investigation, 2 of the participants who smoked less and shared with peers reported inhalations per day, whereas the other participant reported bowls of marijuana smoked per day. This metric possesses limitations because each inhalation and bowl will possess slightly varying amounts of the substance, and participants may have reduced the number of inhalations or bowls but may have increased the depth of inhalation. This can affect what can be said about overall reduction. Nevertheless, this metric was applied consistently across time to allow the detection of changes for each participant. Thus, it is safe to say that the intervention was useful but the exact amount of reduction remains questionable.
A third limitation is that 2 of the 3 participants began using again at follow-up, although at lower rates. Even though it is not reasonable to compare studies, maintenance of treatment gains has been an issue in all other marijuana abuse treatment studies. This is certainly an issue that warrants further attention. One possibility is that moderation rather than abstinence could be a treatment goal for some. This might have been the goal for the 2 participants who were using at follow-up because they chose to start using; 1 of the participants used only on the weekends, which according to his reports, did not interfere with other areas of functioning. Nevertheless, it is unclear why 1 participant was no longer using at follow-up and why the other 2 were using at varying levels. Future research should determine what variables account for long-term improvements in ACT for marijuana dependence.
A fourth limitation is that the data are not totally consistent with regards to assessments of the AAQ, depression, anxiety, and withdrawal symptoms. The means for all participants decreased from pre- to posttreatment with stable or continued decreases at follow-up, but individual patterns are not all consistent with this finding. In addition, the findings on these secondary measures do not closely match the main dependent variable. These issues will likely be clarified through larger and more systematic research and through measure development. For example, across the ACT literature, problem-specific measures of acceptance, defusion, and values correlate better with outcome than general measures such as the AAQ (Hayes, Luoma, Bond, Masuda, & Lillis, 2006
A final limitation is that formal assessment methods were not used for diagnoses of marijuana dependence because of the preliminary nature of the study and its focus on reduction of use over changes in diagnostic criteria. Nevertheless, formal diagnoses allow greater comparison across investigations because they clarify the participants' similarities. Thus, formal diagnostic devices should be used in future studies. In addition, standardized procedures should also be used to assess co-occurring conditions, because they provide insight into who might benefit from treatment.
Even though this study possesses many limitations, it is important to open up new alternatives to be explored. Previous studies on ACT for substance abuse (e.g., Gifford et al., 2004
; Hayes, Wilson, et al., 2004
) suggest that issues that have been championed by clinical behavior analysts for many years (Friman, Hayes, & Wilson, 1998
; Hayes, Jacobson, Follette, & Dougher, 1994
) can be helpful to substance users and can provide an alternative approach to the cravings and urges to use that are seen in substance abuse problems. The present study suggests that well-controlled group-comparison studies of ACT are a logical next step.