This study demonstrated measurable improvement in emotion regulation in women with substance dependence and BPD that received DBT treatment. Improved emotion regulation appeared to be distinct from, and to continue beyond, improved mood. When entered as a covariate, improved emotion regulation accounted for decreased frequency of substance use, suggesting that developing effective emotion regulation skills may have allowed study participants to cease other less effective emotion regulation behaviors. This interpretation is consistent with the DBT model that understands emotion dysregulation to mediate the maladaptive behaviors of BPD in the face of life stressors (2
). These results extend the findings of previous research showing both improved emotion regulation and decreased dangerous impulsivity (i.e., self-harm) with participation in DBT-informed interventions (37
), by specifically showing an association between the improved emotion regulation and decreased dangerous impulsivity (i.e., substance use).
Given that the present results linking improved emotion regulation and decreased substance use are correlational, it is not possible to make conclusive interpretations of causality. For example, the results could alternatively be interpreted as indicating that those who were able to reduce their substance use were then more proficient at developing emotion regulation skills—perhaps comparable to the hindering role of PRN benzodiazepines observed in cognitive behavioral treatments for panic disorder with agoraphobia (39
). Or, it is possible that the observed associations were caused by some interaction of the variables, or by some third unspecified process. However, it is noteworthy that decreased substance use was specifically associated with improved emotion regulation, and not with improved mood (depression), supporting the specificity of this result.
With respect to the dimensions of emotion regulation that were observed to improve in the exploratory analyses, during the first half of treatment patients reported increased confidence in their ability to regulate negative emotions. By the end of treatment, this confidence improved further, and patients also reported increased ability to attend to, identify, and understand their emotions, and to remain in control when experiencing negative emotions.
Only 55.6% of participants completed treatment as defined by DBT protocol attendance requirements (2
), and this finding speaks to the challenges involved with engaging patients with comorbid BPD and substance use disorders into treatment (40
). When treatment attrition occurred, it generally included the patients “falling out” of contact, and therefore the reasons for leaving treatment were generally not available. While there is some indication that DBT is more successful than standard treatments at engaging patients with substance use disorders (21
), the present study’s retention rate is consistent with past studies reporting retention between 52% and 64% (21
). Linehan and colleagues have addressed the challenges of treatment retention with patients that are comorbid for BPD and substance use disorders by developing a variety of “attachment strategies” such as procedures for finding “lost” patients (26
). Although some of these attachment strategies were utilized in the present investigation, such as using telephone contact break cycles of avoidance following patient absences; many of the more intense attachment strategies described by Linehan and colleagues were not utilized, such as conducting therapy in patients’ natural environments or responding to patient absences with token gifts symbolizing the therapists’ pining. It is also noted that whereas Linehan and colleagues included the prescription of drug agonist medication as part of the DBT-SUD treatment for opiate users, the present study prescribed an opiate blocker, and this less reinforcing medication may have also contributed to treatment attrition observed.
A primary limitation of the study is that there was not a control treatment condition. This limits our ability to attribute emotion regulation improvement specifically to DBT treatment. For example, preliminary results from a recent randomized controlled treatment of DBT applied to substance dependence did not find improved emotion regulation to be specific to the DBT treatment condition (26
). Significantly, patients received concurrent psychopharmacological treatment, which could have contributed to the observed improvements in emotional distress and reduced substance use; however, it is noted that with the exception of Nalrexone, the medications prescribed do not typically have large effects on substance use outcome, and psychotropic medications would not be expected to increase efficacy for attending to, accepting, and modulating emotions, as assessed in the DERS. An additional limitation is that the treatment provided was of shorter duration than most previous DBT studies, and based on the pattern of findings observed it is unclear if the full treatment effect was realized. It is noted, however, that there have been several studies of comprehensive DBT of shorter duration than one year, such as a 12- to 16-week adaptation for adolescents by Miller, Rathus, Linehan at collagues (42
) and two 26-week randomized controlled trials (44
Other limitations include the exclusion of men, the under representation of minorities, and the use of clinical interviews for BPD and substance use diagnoses. The study also did not include no systematic assessment of DBT adherence, and therefore problems of adherence cannot be ruled out for contributing to treatment attrition. Further, assessments of substance use included participants' self-report and clinician assessments, all subject to potential bias. Although the substance use frequency variable was a composite that included biological data, this data was collected as part of standard clinical care as opposed to standardized research outcome measures. On the other hand, the present study has the benefit of exemplifying the application of DBT in a standard community substance use clinic setting.
Nonetheless, this is the first study to show improved emotion regulation in BPD patients receiving DBT and to show that such improvement mediates improvement in an impulsive, maladaptive behavior (substance abuse). On the basis of these findings emotion regulation assessment is recommended for future studies of the etiology and maintenance of psychiatric disorders associated with emotion dyregulation, such as BPD and substance dependence, as well as to further explore the potential role of emotion regulation as a mechanism of change for clinical intervention.