Using contingent incentives to target attendance and opiate-negative urines, the present study demonstrated overall improved treatment retention and abstinence among patients in Chinese MMT, although there were considerable site differences. Most incentive effects were observed in Kunming, where the Incentive group performed better than the Usual Care group in treatment retention and completion (75% vs. 44% completed the 12-week treatment). Retention rates in Shanghai were high (about 88%), and patients in the Incentive group demonstrated a long duration of sustained abstinence (7.7 vs. 6.5 weeks) and high percentages of negative samples (74% vs. 68%). Taken together, these results demonstrate the effectiveness of motivational incentives targeted to treatment attendance and opiate abstinence when implemented in community MMT programs in China. The study contributes to the empirical evidence for the use of contingency management to reinforce target behaviors [16
Prior studies using contingency management among MMT patients typically targeted substances other than opiates, such as cocaine or alcohol. Studies that applied contingency management to opiate abstinence have focused on patients who continued opiate use during MMT. One study maintaining patients at a methadone dose of 100mg [23
] found no differences during the intervention regardless of whether the incentive targeted cocaine abstinence or both cocaine and opiate abstinence, but opiate abstinence was greater in the opiate-cocaine group post-intervention. Another study [24
] contrasted methadone dose increases and abstinence reinforcement for treatment of continued opiate use during methadone maintenance. This study found that contingent vouchers and increasing methadone dose significantly increased opiate abstinence during the intervention, but did not dramatically enhance effects when combined. The baseline dose in this study was 50mg and could have reached 70mg. Standard treatment in all of these studies included counseling sessions as are routinely practiced in community treatment.
MMT in China is at an early stage of diffusion. As is the case in other countries new to MMT, service providers and patients in China had concerns that methadone is “yet another drug” and often requested reduced dosages to avoid methadone addiction [25
]. Another unique aspect of MMT in China is that MMT staff members are medical doctors and nurses and the main service is to dispense methadone. Most MMT programs do not have staff specifically trained to deliver psychosocial interventions. Within this context, the present study still demonstrated dramatic decreases in opiate use after treatment entry across study conditions and sites, which is consistent with a large body of international research showing the efficacy of MMT for the treatment of opiate addiction. Reduced opiate use reduces needle sharing and may also reduce the likelihood of risky sex associated with using drugs, all contributing to China’s goal of establishing MMT to reduce HIV [26
]. Nevertheless, there are areas for improvement. Higher dosages and provision of psychosocial support could decrease both treatment dropout and heroin use. Given the current general low-dose practice, behavioral interventions may be particularly useful to maintain patients in treatment, as was shown in Kunming. Although Shanghai patients demonstrated very good treatment attendance and high retention rates regardless of study condition, contingent incentives did improve sustained abstinence. Typical of incentive approaches (as well as other therapies), post-treatment outcomes did not differ between conditions.
There were significant site differences with Shanghai demonstrating fewer intervention effects but overall better outcomes than Kunming. Methadone dosages were similarly low in both sites (about 46mg in Shanghai and 55mg in Kunming), but patient populations varied considerably as reflected in the many differences in baseline characteristics. Social workers in Shanghai may have played an important role promoting more favorable patient outcomes overall. Shanghai’s relatively higher economic status may have also reduced the attractiveness of study incentives (e.g., of the 54 patients that refused participation, 53 were from Shanghai). Currently, all patients in China pay 10 Yuan per day for methadone, which could be a barrier for Kunming patients who are generally poorer. Future studies should explore if varying incentive amounts for populations of different socio-economic status may optimize outcomes for respective patient populations. Because intervention effects vary by site, replication of findings and inclusion of more sites would increase confidence in intervention effectiveness. Furthermore, the incentives earned by Kunming participants were more for attendance than for abstinence. Future studies should examine how incentive schedules could be altered to improve substance use outcomes while still maintaining attendance. As for other study limitations, despite the effects of the intervention on retention, attrition remained high (particularly in Kunming) which reduced power for some analyses. Similar studies have not been conducted in China previously to inform power calculation. Thus, the sample size for the present study was determined by considering several U.S. contingency management studies as well as resources available to the study. The study sample size had sufficient power (80%) for primary outcomes, e.g., an effect size of 0.31 for a continuous measure (e.g., treatment retention) with alpha at 0.05. Future studies taking attrition into consideration may find that a larger sample size, (e.g., 400 participants) will detect a smaller effect size of 0.28 in testing the intervention effect in ANOVA analyses.
Overall, methadone-maintained patients in China can benefit from reinforcement of attendance and abstinence. A small investment (371 Yuan per person; less than 5 Yuan per day) can produce sustained abstinence and longer retention. The observed site differences also suggest that incentives are useful for solving a problem (poor retention, high drug use rates) in some areas (e.g., Kunming), but may not be worthwhile when applied to other areas. Given the current widespread endorsement of low-dose practices among patients and providers in China, a behavioral intervention reinforcing attendance and abstinence should be considered, particularly in areas with few resources and social support.