The purpose of this study was to compare the effectiveness of an established but complex and expensive behavioral day treatment intervention with only its abstinence contingency managed components, the latter of which could possibly serve as a first step care for homeless persons with cocaine and other drug dependence. Three important results were obtained. First, high retention and abstinence levels were achieved by participants in both the abbreviated (CM) and full (CM+) interventions. Abstinence levels were higher than those of our three previous studies with this population (Milby et al., 2000
). Second, as hypothesized, the CM group achieved high and sustained abstinence throughout active treatment, which was not significantly different from, nor inferior to that of the more intense and expensive CM+ treatment. Third, distal outcomes of greater sustained abstinence, 6 and 12 months after treatment, emerged in the CM+ group. Similar delayed effects of substance abuse treatments have occasionally been reported by others. For example, a delayed effect was observed for relapse preventionbased behavioral psychotherapy in cocaine dependent patients treated with pharmacotherapy (Carroll et al., 1994
). Also, Rawson and colleagues (2002)
found delayed effects of cognitive behavioral therapy for cocaine dependent patients treated for opioid dependence with methadone maintenance.
These results may have policy implications for the utilization of the CM components as the first step in a stepped care model for homeless substance abusers, in which only those who fail to respond to initial stepped care would be referred for the intensive and more costly behavioral day treatment utilized in CM+. However, further study is needed before we could know if the response to CM+, given its sequential exposure to CM, is the same as response to CM+ only. The relative success of the CM intervention suggests that further reductions in its complexity as an initial step of care should be studied. For example, abstinent contingent housing alone may be a sufficient intervention for homeless substance abusers to initiate and sustain abstinence without further substance abuse treatment, especially for those with non-complicating mental disorders.
In our earlier clinical trials (Milby et al., 2000
), enhanced behavioral interventions maintained their significant effects on abstinence after statistically controlling for attendance. In the present study, controlling for attendance neutralized the effect of treatment. This suggests that CM+ gained its treatment superiority by retaining participants. By extension, we infer that if CM were to be modified to be more attractive and retain more participants, it could be more effective and potentially more cost effective, depending on the cost of such enhancements. Clearly, more research is needed here to determine whether these important implications can be verified in future research. The complete results suggest an ironic demurrer with an opposite policy implication. It may be that the long term outcomes achieved here may not be possible if we continue to insist that treatment be less expensive and less complicated.
The small advantage of behavioral day treatment over the contingency managed housing and work during active treatment, may indicate that CM outcomes approach a ceiling of reasonably expected levels of abstinence for this population beyond which it is difficult to yield further gains. Thus, CM alone may be a relatively inexpensive but nevertheless viable intervention, perhaps capable of helping a substantial proportion of homeless substance abusers initiate and sustain abstinence while concentrating on improving their housing and employment conditions. That abstinence for CM+ was significantly higher than CM during the post-treatment period (months 7–18), may indicate that gains in recovery resulting from behavioral day treatment are best reflected in long term reduced drug use and perhaps better life functioning, like long term housing stability, employment, psychiatric status improvement, and health care service utilization. Thus, CM+ may be a more viable alternative for a homeless cohort with more psychological problems in addition to chronic addiction. This possibility is suggested by other studies with this population.
Lester et al. (2006)
studied PTSD symptoms in a subset of the present sample, and found more improvement in these symptoms among participants in the CM+ condition. Also, our research group (2001) examined the relative treatment response of participants with substance use disorders only compared to those with one or more additional DSM III-R Axis I disorders. All received behavioral day treatment like the current CM+ condition. Those with dual diagnoses showed greater positive changes than the substance use only group from baseline to six months, in alcohol, drug, employment/support, and psychiatric status areas. Although this pattern may reflect a regression to the mean, those results also are consistent with the notion that behavioral day treatment has important impacts on life functioning in addition to abstinence effects. Another example of more persistent treatment effects other than improved abstinence, was found by Higgins et al. (2003)
. They studied the effect of contingency management alone compared to CM plus an intensive behavioral community reinforcement approach, similar to CM+ in the current study. Two years after treatment entry only the added behavioral intervention showed improvement in drinking to intoxication, more days of paid employment, fewer hospitalizations and legal problems.
Results from the current study, together with the PTSD subpopulation, and the earlier study from a similar cohort treated with the behavioral day treatment, suggest some functioning domains where behavioral day treatment may exert delayed treatment effects. Future research needs to replicate those effects to identify what additional participant characteristics change, other than improved long term abstinence. Research identifying such associated changed characteristics in the delayed treatment effect would seem to have implications for matching patients to either of these interventions in the most cost effective manner.
In addition to the question of what patient characteristics or behaviors change most during and after treatment, there also is the possibility of identifiable pre-treatment characteristics that predict favorable outcomes for the CM and CM+ conditions. Future analyses of these data and from other long term outcome studies may provide such predictors. Perhaps a more useful predictor of treatment outcome may be early treatment response. We and others have found that those participants who initiate and sustain abstinence early in treatment, to a great extent irrespective of the treatment to which they are assigned, show more sustained abstinence at distal follow-up after formal treatment has ended (Carroll et al., 1994
; Higgins, Badger, & Budney, 2000
; Kosten et al., 1992
; Milby et al., 2004
The current study results and our previous work using abstinent contingent housing, (Milby et al., 2000
) may appear to have very different implications than current and highly-publicized initiatives in what is termed a Housing First approach (Editorial, 2002
; Ekholm, 2006
; HUD, 2002
; Tsemberis, Gulcur, & Nakae, 2004
), where housing is offered directly to homeless persons, without preconditions other than provision of payment and/or agreement for a case manager to visit. Patients in the Tsemberis et al. continuum of care control group received access to housing based on substance abuse and psychiatric treatment participation and established abstinence. However, their abstinence outcomes, that were not different from the housing first group, may be a function of the different populations served. A harm reduction, housing first intervention may be more appropriate for homeless persons with severe mental illness studied by Tsemberis, and colleagues. For populations with non-psychotic mental illness and cocaine dependence, behavioral intervention, which offers housing for treatment participation in the first week, then imposes an abstinence contingency for continued housing, may be the most viable approach. These important treatment access and policy concerns should be addressed in future research designed to compare these options.
These results seem consistent with the Rawson, Huber, McCann, et al. (2002)
results comparing Cognitive Behavioral Therapy (CBT) with Contingency Management (CM) alone, and both of these treatments alone with combined CM+CBT. At six and 12 month follow-ups, the superiority of CM over CBT observed during treatment disappeared, while performance of the CBT group appeared to improve over time. The Higgins group (2003)
also found benefits two years after treatment entry from their behavioral intervention added to contingency management. These gains were observed 1.5 years after contingencies ended. Thus, findings are accumulating to suggest that intensive contingency management approaches when combined with cognitive behavioral therapy may be able to sustain treatment gains long after contingencies are discontinued.
Though cost and complexity are obvious barriers to implementation of this effective intervention, there are others that are less apparent. Thus, this study is only an initial step toward determining how this intervention can be disseminated. Effective implementation of CM is more complicated and requires more skill than people generally believe. It probably requires faithful adherence to manualized procedures and progressive steps of measured training like that utilized by Milby and colleagues in the Houston, Texas replication study (Milby et al., 2007
). It may be that the most important barrier to acceptance and dissemination of CM (and CM+ for that matter) may be its conceptual acceptability to treatment providers and other stake holders.
Some limitations of the study should inform the interpretation of findings. Though missing data was reduced to lower levels than ever obtained by our research group studying this difficult population, it still requires interpretation, particularly when urine tests were more frequently missing for CM than for CM+. It could be that missing data contributed to differences in observed abstinence, because missing data points were coded drug-positive. First it should be noted that a finding of greater long-term abstinence in the trial arm with the least missing data (or conversely, the strictest scrutiny, as was the case for CM+ here) is generally likely to be a valid one. Second, since both groups had the same housing and work training incentives to lose from missing a urine test, and the same benefits from giving urine specimens testing free of abused drugs, it is likely a valid assumption that missing a urine test unexcused indicates drug use. If participants in either group were clean and missed a drug test they would lose these incentives in spite of being abstinent. The disparity in excused missing urine tests where CM+ had more excused missing tests may have contributed to abstinence outcomes. We attribute this finding to the fact that the CM+ group spent twice as much time in Phase I treatment, from 7:30 to 4 pm, and needed more excused absences to complete important community recovery tasks. Lastly, it is important to note that our participants were all treatment seekers and thus generalization to a population of homeless substance abusers, many of whom do not seek treatment, may be limited.