In the present study, we examined the efficacy of a brief but intensive voucher-based CM intervention for reducing cigarette smoking among MM patients. Despite a high prevalence of smoking in this population and numerous reports of interest among MM smokers in quitting, previous efforts at smoking cessation in this population have produced generally modest results. One likely reason for this is that procedural limitations in prior studies that have targeted smoking among MM patients may have limited their efficacy.
The present study demonstrates that a voucher-based CM intervention can promote smoking abstinence in MM patients. Participants in the contingent group provided a greater percentage of abstinent samples and achieved a longer duration of continuous abstinence than did those in the noncontingent control group. This was evident across all measures of smoking throughout the study, including breath CO levels, urine cotinine levels, and number of cigarettes smoked. These findings provide evidence that CM can be effective in promoting smoking abstinence in MM patients.
The methods used in the present study differed in several ways from those used in previous studies. First, a schedule of daily biochemical monitoring was used that was more intensive than the twice- or thrice-weekly schedule typically used in prior studies (Schmitz et al., 1995
; Shoptaw et al., 1996
). Second, the schedule of reinforcement in the current study included several features (e.g., escalating schedule, reset, bonuses) shown in prior studies to help promote abstinence (Roll & Higgins, 2000
; Roll, Higgins, & Badger, 1996
) and used a relatively high magnitude of incentives. Voucher magnitude has been shown to significantly influence amount of abstinence achieved in CM interventions (e.g., Silverman, Chutuape, Bigelow, & Stitzer, 1999
). In the present 2-week study, the total earnings possible (i.e., $362.50) were substantially higher than amounts used in prior studies. For example, total possible earnings in the 2-week contingent phase of the Schmitz et al. study were $20.00, and earnings in the 4-week phase by Shoptaw et al. (1996)
was $73.00. Although maximum possible earnings in the more recent 12-week study by Shoptaw et al. (2002)
totaled $447.50, only approximately $29.50 was available for continuous abstinence during the important initial 2 weeks of the study. Third, the present study used a CO-to-cotinine method to carefully monitor smoking status, enabling us to reinforce initial smoking abstinence early in the study and then to move to a more sensitive test that was likely to detect even low levels of ongoing smoking later in the study. Consistent with prior research by our group (Higgins et al., 2004
), this method appeared to be effective for promoting smoking abstinence in the present study. Finally, the present study employed a rigorous scientific design that included randomization to experimental groups, stratification on a subset of variables thought to potentially impact outcome, and a noncontingent control group who received vouchers independent of smoking status and were yoked to contingent partners. Overall, it is likely that these procedural features helped to improve rates of smoking abstinence compared to the outcomes seen in prior studies.
Although the intervention used in this pilot study was brief, it demonstrated the efficacy of a behavioral intervention in promoting early continuous cigarette abstinence in MM patients. Considering that a positive relation between early initial smoking abstinence and longer term outcomes has been well documented (Gourlay et al., 1994
; Higgins et al., 2006
; Kenford et al., 1994
; Yudkin et al., 1996
), the promising levels of initial smoking abstinence with this 2-week intervention bode well for longer term outcomes. Indeed, if initial continuous abstinence can be established with an intensive intervention early in the quit attempt, it may then be possible to maintain that abstinence with a monitoring schedule that becomes progressively leaner over subsequent weeks. Future efforts by our group will be aimed at developing a CM intervention that sustains smoking abstinence for the longer term.
Several limitations are relevant to this pilot study. First, this study was conducted with a limited sample size. Future studies should attempt to replicate and extend these findings with a larger number of participants. Second, relatively stringent criteria were used to ensure that participants were stable and abstinent from illicit drug use before participating in this study. It would be important to learn whether the same positive smoking outcomes would be seen in MM smokers whose illicit drug status was less stable. However, it also should be noted that this criterion did not appear to be so restrictive as to significantly limit the generality of these findings. For example, approximately 75% of this methadone clinic's general patient population met the illicit drug criterion at the time the study was conducted, and our study criteria prevented only 17% of interested patients from participating. That said, the need for this criterion should be evaluated during future efforts to replicate the current study in clinics with perhaps less stable patient populations. Third, the results of this pilot study were achieved in the absence of any nicotine replacement therapy (NRT). Use of NRT would have interfered with our use of urine cotinine as a biochemical measure of smoking, because it would have been impossible to distinguish NRT-derived cotinine from that produced by cigarettes. However, the biochemical testing methods used in this study do not preclude the use of nonnicotine pharmacotherapies for smoking cessation, such as bupropion. Bupropion has been shown to aid smoking cessation efforts to a similar degree as nicotine-based pharmacotherapies (Hughes, Stead, & Lancaster, 2004
) and has been well tolerated in several prior studies with MM patients (Margolin et al., 1995
; Margolin, Kosten, Petrakis, Avants, & Kosten, 1990
It should also be noted that even though some group differences were still evident in the weeks following the study, a subset of contingent participants had relapsed to smoking. Indeed, inspection of individual data showed that some contingent participants continued to smoke during the intervention. For example, although 5 of the 10 contingent participants achieved nearly complete levels of abstinence, a subset achieved either little (3 participants) or no (2 participants) abstinence (). Even though a core of treatment-resistant participants is typically seen with substance abuse treatments in general, it is important to explore ways to further increase the number of participants who respond favorably. Increasing incentive magnitude (e.g., Silverman et al., 1999
) or using shaping procedures (e.g., Lamb, Morral, Kirby, Iguchi, & Galbicka, 2004
) or adjunct pharmacotherapies may be useful approaches with particularly hard-to-treat smokers. It also would be of interest to learn whether those individuals who responded well to these relatively high voucher values might also respond to lower magnitudes. Finally, it is worth investigating the characteristics that may distinguish the individuals whose smoking is sensitive to voucher-based CM from those whose smoking is insensitive.
In summary, the present study demonstrates the efficacy of a brief voucher-based CM intervention in promoting initial smoking abstinence among MM patients. The development of effective smoking cessation programs in this treatment setting holds potential for wide dissemination. The possibility of extensive and cost-effective implementation is also enhanced by the fact that many components of routine MM treatment, such as dosing and ancillary services, can themselves function as reinforcers and be arranged contingently to promote positive behavior change (Kidorf & Stitzer, 1999
). Overall, these preliminary results suggest that behavioral treatments (e.g., contingency management) offer significant promise for treating cigarette smoking among MM patients.