Whereas the efficacy of psychosocial interventions for the treatment of cocaine dependence has been demonstrated (Carroll, 2005
; Dutra et al., 2008
; Woody, 2003
), there is an ongoing debate whether different psychosocial interventions are equally effective or some are superior to others (Carroll et al., 1998
; Crits-Christoph et al., 1999
; Higgins et al., 1993
; Maude-Griffin et al., 1998
). In this study, we examined differential effects of the four psychosocial interventions for cocaine dependence evaluated in the NIDA CCTS (IDC, CT, SE, and GDC) in subgroups of cocaine dependent individuals. Using GMMs, we identified three distinct patient subgroups on the basis of similar initial impairment and change during treatment in the target outcome behaviors of treatments for cocaine dependence–in cocaine use and in overall drug use.
There was a first patient subgroup including more than half (52%) of the patients in our study. Compared to the two other patient subgroups identified in the study, these “common and fast responders” entered treatment with moderate cocaine use and with moderate overall drug use, and they then experienced a very rapid reduction of cocaine and of overall drug use already in the first month of treatment irrespective of the type of psychosocial treatment. These “common and fast responders” also retained their benefits over a one-year period after treatment termination, and there were again no differential treatment effects over this follow-up period indicating that there were no delayed differential effects of professional psychotherapies (CT and SE) as they have been reported in previous studies (Carroll et al., 1994b
). These findings suggest that the type of psychosocial treatment does not matter for a large subgroup of patients with cocaine dependence; the common cocaine dependent individual seems to benefit clearly and to the same extent from each of the four psychosocial interventions. Interestingly, this seems to apply even for a minimal intervention such as GDC. If this finding would be replicated in future studies, then other criteria than efficacy (e.g., different costs of treatments) may gain importance when deciding which psychosocial treatment to provide to these patients.
However, when comparing the outcomes of IDC, CT, SE, and GDC alone in terms of sample means, Crits-Christoph et al. (1999)
found IDC to be superior to the other three psychosocial interventions in reducing cocaine use as well as overall drug use. According to our findings, this superiority of IDC seems to be mainly attributable to better outcomes of IDC in a subgroup of “moderate responders.” This patient subgroup included about one third (35%) of the patients and was characterized by very similar initial cocaine use and overall drug use as the subgroup of the “common and fast responders”, but the moderate responders then, on average, experienced a clearly less rapid reduction of overall drug and of cocaine use during treatment. Predictor analyses to identify patient characteristics that are indicative for these “moderate responders” revealed that, compared to the more rapid responding “common and fast responders”, the “moderate responders” had more social and environmental problems and reported lower endorsement of the philosophy and behaviors advocated in the 12-step programs at the beginning of treatment. If replicated, these findings suggest that IDC might be a specifically appropriate treatment for moderately severe patients with a psychosocial environment detrimental to recovery (low support of family, friends, or others in the patient's home setting) and with low endorsement of the 12-step philosophy who are prone to only moderate improvement during treatment. (Note that even though these “moderate responders” were characterized by low baseline endorsement of the 12-step philosophy, they seem to benefit most of IDC which relies on the specific stages, tasks and goals based on this philosophy).
Whereas these “moderate responders” cannot be discriminated from the “common and fast responders” in terms of the magnitude of drug use when entering the treatment, there was a third subgroup of patients (about 13% of the patients in our study) who were characterized by high overall drug use and cocaine use. Like the “moderate responders”, these “severe users” also reported more environmental and social problems and lower endorsement of the 12-step philosophy at baseline compared to the “common and fast responders.” Additionally, they also reported less resistance to treatment. Taking into account that the respective subscale of the RAATE-CE includes items asking whether a patient is aware of and accepts having an addiction problem and whether he or she is open to treatment, the severe users seem no longer to be able to deny their addiction problems and their need for treatment as a consequence of their severe drug use. During treatment, they then reduced their cocaine and overall drug use moderately, and it seems that the type of psychosocial intervention does again not matter among these severe users. The magnitude of the reduction of overall drug use and of cocaine use during active phase treatment resembled the one among the moderate responders with moderate improvement. However, the “severe users” then experienced a continued reduction of substance use during the booster phase (i.e., up to the assessment at month 9 after baseline; see ), though particularly their cocaine use then again increased during the subsequent 3 months. Whereas their overall drug use approached the level of the moderate responders during the year following active phase treatment, they consistently reported higher cocaine use during this phase. These findings suggest that longer treatments might be necessary among severe cocaine users. Taking into account the relatively high drop out rate in this subgroup, clinicians should also be aware to take further measures to aid in the patients retention in this subgroup in order to enhance treatment outcomes among the severe users.
In this study, we demonstrated that several subpopulations can be distinguished among cocaine dependent individuals in terms of initial cocaine and overall drug use and their change during psychosocial interventions. This finding of different treatment courses is clinically appealing and consistent with previous findings from psychotherapy research (Barkham et al., 1993
; Lutz et al., in press
; Stulz and Lutz, 2007
; Stulz et al., 2007
). However, our patterns of change differed somewhat from those found by Morral et al. (1997)
in another substance use sample. Possible explanations for these differences might be that the 4 response classes identified by Morral et al. (“improving”, “stable-good”, “stable-poor”, and “deteriorating”) were found in a diagnostically different sample (opioid-dependent methadone maintenance patients), based on a different outcome measure (monthly assessed urine specimens) and extracted with a different method (cluster analysis).
Furthermore, although psychotherapy research often failed to find clear outcome differences between different treatment schools (Luborsky et al., 2002
; Luborsky et al., 1976
; Wampold, 2001
), our findings suggest that this is not necessarily true for cocaine dependent patients when using methods that sufficiently account for the heterogeneity among patients. In fact, our findings suggest that different psychosocial treatments for cocaine dependence may have a different impact on the course of substance use in different subgroups of patients. The superiority of IDC to other treatments found in previous analyses of the CCTS data (Crits-Christoph et al., 1999
) seems to apply for moderate responders with high social problems and low initial endorsement of 12-step treatment philosophy but not for other patients. In line with findings from previous research (Cuijpers et al., 2005
), our results therefore suggest that treatment research should give sufficient consideration to the heterogeneity within samples of patients to provide a thorough evaluation of the efficacy of different interventions.
Finally, our research basing on typical patterns of change in drug use during treatment can also strengthen the research on moderators of treatment effects. If patient baseline characteristics that enable allocation of patients to subgroups are identified, then this allows us to predict for a specific patient already at intake from which type of treatment he or she will benefit most (or whether the type of treatment does most probably not matter for that specific patient). Such predictions of individual treatment courses furthermore might then also be used as benchmark to monitor and evaluate the actual treatment progress of an individual patient and to immediately feed back this information to therapists in the field of patient-focused research (e.g., Haas et al., 2002
; Howard et al., 1996
; Lutz et al., 2005
; Lutz et al., 1999
However, our study also has some limitations: First, because these analyses were post-hoc exploratory analyses, further research is necessary to examine whether the three patient subgroups that have been identified in our study are typical for patients with cocaine dependence, especially since we draw a subsample from the original CCTS sample that only included those patients with enough assessment to conduct our complex longitudinal analyses. This selection may have affected our findings. Second, it should be kept in mind that the data of the CCTS was generated under controlled conditions which brings some limitations concerning external validity. Therefore, further research should examine whether the typical patterns of drug use are also found in naturalistic settings and in routine care. Third, due to the quite small number of subjects in the severe users subgroup (which is related to a low statistical power), the findings concerning this subgroup should be treated with caution. Fourth, it remains unclear whether our findings also generalize to cocaine patients with more severe psychiatric comorbidity as current psychotropic medication was an exclusion criterion in the CCTS. Fifth, if available, weekly collected urine specimens were used to examine the validity of self-reported drug use as measured by the ASI. Only 15% of the urine tests indicated some drug use during a month when the patient denied use. Despite this good agreement between urine test results and self-reports of cocaine use, whether patients were using cocaine at times when no urine assessments were available is unknown. And finally, future studies should also examine additional predictors as well as change in other (e.g., biomedical) outcome measures.
Despite these limitations, our findings suggest that there is significant heterogeneity among patients with cocaine dependence and that the effects of psychosocial interventions might be different for different subpopulations of patients. Such findings can then also be helpful for patient classifications that indicate which treatment is most effective for which type of patient.