This study adds to the evidence for differential effects of IT by examining post-intervention service use as conditioned by the intervention across distinct clusters of women. Women with co-occurring disorders and histories of abuse traditionally have considerable unmet need for specialized, integrated treatment services (SAMHSA 2002
). The IT intervention has been shown to improve outcomes while not significantly increasing costs of services utilization. The challenge is to understand how best to provide these intervention services, by first identifying differences in the effect of the intervention across this heterogeneous group of consumers.
The intervention appeared to increase the efficiency of service use for some women in this study population—in other words, moving them toward an optimal balance between need for services based on symptomatology and intensity and mix of service use. The intervention was associated with reductions in counseling use for some women in this study population and increases in residential treatment use for others. Reductions in counseling use may have been evident because the women received trauma-informed, integrated counseling that addressed multiple needs—including trauma symptoms—in a single service setting rather than having to access a collection of separate services across various, fragmented service settings. Increases in time spent in residential treatment may have, for many, indicated improvements in service use efficiency by increasing their use of targeted services to better meet their treatment needs. The effect of IT on changes in efficiency of service utilization was variable across sub-groups, however, depending upon women's symptomatology and utilization patterns upon entering treatment.
Women who were characterized by low symptom severity at baseline and who were in the IT group may have actually used services inefficiently, as they used relatively high levels of residential treatment at follow-up as compared to their counterparts in the usual care group. Cusack et al. analyses (2008)
found that IT had no effect on clinical outcomes among women who had low symptom severity at baseline, though their cluster assignments did not correspond exactly to those generated in these analyses. Together, these findings suggest that there was a mismatch between symptoms and service intensity for these women; their needs might have been better met by less intensive outpatient and support services. It is also possible, however, that higher relative use of residential treatment among women with low symptoms in the intervention group could reflect better treatment engagement, particularly if women in the control group used fewer days due to detrimental circumstances such as substance abuse relapse. That said, there is no reason to expect that the women with low symptom severity in the intervention group differed in a systematic way from their counterparts in the usual care group in terms of relapse risk or other characteristics other than their study group assignment.
Among women whose predominating symptom at baseline was moderate-severe PTSD, on the other hand, these study results suggest that IT was associated with more efficient service use. Women in this cluster who were assigned to IT used less outpatient counseling and more residential treatment at follow-up relative to their counterparts in the usual care group. Considering that women with this symptom profile were demonstrated in earlier work to be the major beneficiary of IT regarding clinical improvements (Cusack et al. 2008
), a shift from outpatient counseling use among these women to more days in residential treatment was likely beneficial to their clinical functioning, thereby indicating improvement in the efficiency of intensity and mix of their service use.
Interestingly, no differences in the effect of the intervention on outpatient counseling use at 12 months were detected when women were clustered according to their baseline service patterns. In this case, baseline service use behaviors alone appeared not to moderate the intervention effect in the same way that symptomatology did, which for the counseling use outcome countered our expectation for its superior predictive value of effect measure modification.
The IT intervention was associated with more days spent in residential treatment as compared to usual care for several other sub-groups of women. Among two subgroups of women who suffered severe symptoms of substance abuse and PTSD—women with high drug addiction and PTSD, and women with severe comorbidity for drugs, alcohol and PTSD—and who were in the IT group, a relative increase in use of residential treatment appeared to indicate an appropriate increase in their service use, particularly considering women with these symptom profiles had active substance abuse problems for which residential treatment may be most appropriate and that they demonstrated significant clinical improvements in analyses by Cusack et al. (2008)
Similar IT effects on residential treatment use were also demonstrated by certain sub-groups of women when characterized by their baseline service use patterns. Women who were low-intensity service users and in the IT group used more residential treatment at follow up than their counterparts in the usual care group. This cluster of women may have been under-served in the pre-intervention period, particularly considering almost 80% of them had some combination of severe substance abuse or trauma symptoms at baseline. If so, relative increases in their use of residential treatment likely reflected an appropriate shift in service utilization to meet their treatment needs. Additional analysis of the changes in symptomatology at follow up specifically for women with low baseline service use would add more context for their increased use of residential treatment, particularly considering it is a highly resource-intensive modality of treatment (Dickey and Azeni 1996
; Barnett and Swindle 1997
; Roebuck et al. 2003
) and interrupts women's lives and roles in their communities.
Women who used moderate levels of residential treatment at baseline and were in the IT group spent more days in residential treatment by 1 year than similar women in usual care. The large majority of women in this sub-group characterized by moderate residential treatment use at the start of the study also had some combination of severe symptoms at baseline, which suggests that relatively higher intensity use of this targeted type of treatment was likely appropriate and demonstrated improved efficiency in their service utilization. This finding also suggests that the intervention worked to boost or sustain the use of residential treatment for women who were already engaged in it in a way that usual care did not.
A key contribution of this study is the identification of differential effects of the IT intervention on service utilization within a heterogeneous population of women with co-occurring disorders and histories of abuse, adding to the existing evidence for its heterogeneous effects on clinical outcomes (Cusack et al. 2008
). The assumption of a homogeneous treatment response is often unreasonable without empirical evidence to support it (Manski 2001
). Therefore, differential treatment response should be estimated according to important moderators—in this case, symptomatology and service utilization patterns—in an effort to work toward maximizing the benefits of treatment for different types of women in this population. Both average effects of IT within the population and sub-group effects of IT according to defining characteristics can help policymakers understand how IT works in the population at large, as well as by whom specifically it is used most and least efficiently. Integrated treatment like the intervention studied here is resource intensive and should be targeted to people who have a demonstrated need for it according to their symptomatology and/or service use patterns. Conversely, other people who are functioning well could benefit equally from less intensive usual care services.
There are limitations to this study that are important to consider. First, a quasi-experimental study design can introduce biases through unbalanced treatment groups and differential attrition as described earlier. A benefit of non-random recruitment is that the resultant study groups were more representative of women who, in the real world, may be targeted to receive IT services and others who remain in settings where they receive usual care. Secondly, making the assumption that treatment assignment was the equivalent of treatment receipt may have biased results if participants in the usual care group were actually receiving IT-type services. There is evidence, however, that differences in intervention and comparison program content in this study were associated with differential improvements in outcomes attributed to the intervention (Cocozza et al. 2005
). Further, unmeasured receipt of IT-type services by participants in the usual care group would attenuate the intervention effect, biasing the estimates downwards and producing conservative results.
The shortcoming of using an arbitrary number of clusters was mitigated by use of specification tests and other analytic tools for assessing the sensitivity of the cluster results. This included conducting several iterations of the clustering process using different variable scaling approaches, and re-generating effect estimates after combining similar clusters to detect any differences in the effect of IT on sub-groups of study participants.
While insurance variables are invariably endogenous, endogeneity bias is arguably minimal in these analyses for two reasons. Model estimates of the effect of IT on outcomes were not significantly different when estimated without a control for insurance status. Second, the presence of a covariate for serious physical illness or disability is an exogenous variable that likely accounted for some of the unique effect of insurance status.
While the characterization of women's symptomatology or service use at baseline in part drove changes in counseling or residential treatment utilization over time, there is no reason to expect that the influence of their baseline profiles would have operated differentially across study groups within the respective clusters. Therefore, unique effects on counseling and residential treatment use that were demonstrated in the IT group versus the usual care group for different sub-groups of women according to their baseline profiles are likely attributable to the intervention and not artifacts of selection bias or regression toward the mean.
Women who are characterized primarily by PTSD, severe drug addiction and PTSD, or severe comorbidity generally responded to the intervention by using more residential treatment than their counterparts in usual care. When considering this new evidence about service use by women with these symptom profiles along with existing evidence of IT improving their clinical functioning (Cusack et al. 2008
), IT in residential treatment settings should be encouraged for women with these symptom profiles. Women with histories of low service use also responded to the intervention by using more residential treatment, a central mode of treatment for people with co-occurring disorders. For these groups of women, the increase likely signaled a shift to more efficient service use by increasing their use of targeted treatment for co-occurring disorders.
The findings presented here provide useful information for service providers and the agencies in which they work. Expected number of services provided is an important measure for provider and agency planning related to capacity, staffing, and other resources. This will be particularly important for agencies that provide integrated treatment in residential settings, as IT was associated with more time spent in residential treatment for several groups of women in this study population.
Practitioners who treat women in this population can use this information to encourage engagement in integrated treatment in residential settings among women in the population with active symptoms of addiction and PTSD. There is also an opportunity based on these findings for service providers without diagnostic expertise to identify consumers in this population who are not using treatment services regularly, and attempt to link them to integrated treatment with the expectation that it may lead to their using more residential care. In the interest of maximizing scarce public resources, program directors and policymakers can use this evidence to focus their targeting of this effective though resource-intensive type of integrated treatment toward the women in this population for whom it appeared to work best—those with severe substance abuse and PTSD symptoms. Finally, the evidence presented here presents an opportunity for future research that would look more closely at the provision of integrated treatment in residential settings, and identify factors within those contexts that are associated with optimal clinical and service outcomes among women with co-occurring disorders and trauma.
Alternatives should be considered for women in this population with low-severity baseline symptoms, as they had relatively large increases in their use of residential treatment and, in other work (Cusack et al. 2008
), were found to have no change in clinical symptoms. Particularly considering that resources for mental health and substance abuse treatment are constrained, efforts should be made to direct women with this symptomatology to use less resource-intensive outpatient services.
Despite a body of evidence demonstrating the benefits of IT without significantly increased costs, this type of integrated, trauma-informed care is not readily available in most communities. Until it is diffused more widely, professionals involved in the planning, implementation, and administration of treatment services for people with co-occurring disorders should consider targeting IT to the sub-groups of women represented in this study population who appeared to benefit most from the intervention in terms of efficient use of appropriate treatment services.