Consistent with this principle, studies of psychotherapy for patients with BPD have demonstrated reductions in self-reported depressive symptoms.8 While some pharmacotherapy trials have also demonstrated reductions in depressive symptoms, this finding is difficult to interpret.1In these studies, patients with comorbid MDD were excluded, so although the pharmacotherapeutic intervention led to a reduction in subsyndromal symptoms of depression, remission rates in patients with comorbid BPD and MDD could not be evaluated. Results from studies of the combination of medication and specialized psychotherapy have been mixed.9 This evidence generally supports the conclusion that treatment of BPD leads to improvement in depressive symptoms, and that psychotherapy plays a more important role than pharmacotherapy in the treatment of BPD with comorbid MDD.
If a patient with BPD has comorbid bipolar disorder type I, question whether there is a personality disorder at all; at least in some patients, intense affective lability or emotional dysregulation can produce similar symptoms. Comorbid bipolar disorder type II is a more complex problem, and it is a heterogeneous entity whose treatment remains controversial. Gunderson and colleagues10 found a comorbidity rate of 19% for bipolar disorder type II. Lower rates were reported by Paris and colleagues.11 The prevalence of this comorbidity depends on how strictly one defines hypomania. However, for the subset of patients in whom these comorbid disorders are clearly and accurately identified, mood stabilizers are required for the treatment of bipolar disorder and specialized psychotherapy is required for the treatment of BPD.
The course of anxiety disorders is similar to that of MDD comorbid with BPD. Good results have been shown with psychotherapies, which suggests that this comorbidity may also benefit primarily from a specialized psychotherapy designed for BPD.8 PTSD is a more complex problem, since its boundaries are not always clear. Some evidence suggests that trauma can worsen BPD, but it is important to remember that not all patients with BPD have histories of trauma and only a small minority of people who experience trauma develop BPD. However, evidence-based psychotherapies, such as dialectical behavior therapy (DBT), tend to focus on the present and short-term future, but in some cases, time-limited, evidence-based cognitive-behavioral therapy for PTSD may be useful.
The presence of a substance use disorder is particularly important and problematic. Some research suggests that the presence of a substance use disorder is associated with more severe BPD symptoms and a poorer prognosis over the intermediate term, but the prognostic importance of substance use disorders may attenuate over time.12,13 Treatment studies for BPD with comorbid substance use disorder suggest that successful psychotherapy can lead to reductions in both BPD symptoms and substance use.14 One study found added benefit from the use of a DBT-based smartphone application in reducing substance use urges.15
Thirty-seven-year-old Nancy is being treated by a psychologist for long-standing depression and anxiety. She is referred for psychiatric assessment, and on the basis of a clinical interview augmented with a semi-structured interview, she receives a diagnosis of BPD. Current comorbidity includes MDD, panic disorder without agoraphobia, cannabis dependence, and alcohol(Drug information on alcohol) abuse. In a collaborative decision, it is decided that Nancy would switch from her current therapy to a DBT program for BPD.
Antidepressant therapy is started but is of limited benefit. Over several months, BPD symptoms begin to resolve, which leads to a similar reduction in her anxiety and mood symptoms, but her alcohol use temporarily worsens. She is counseled to attend a substance use rehabilitation program concurrently with her DBT but feels unable to commit to that much treatment at one time. Her clinicians suggest that she take a temporary leave from psychotherapy until she completes substance use treatment. Once the rehabilitation program is finished, Nancy returns to the DBT program and shows significant treatment gains. After a year, she no longer meets criteria for BPD or any comorbidity.
When eating disorders are comorbid with BPD, rates of eating disorder decline over time, but change to another eating disorder, which is frequently eating disorder not otherwise specified. This suggests that these symptoms can be an impulsivity symptom of BPD. Little research has been done in the population of patients with both BPD and an eating disorder, and a preliminary study that used an adaptation of DBT had mixed results.16 If a patient has serious weight loss resulting from anorexia nervosa, this should be treated before undertaking therapy for BPD. In contrast, binging and purging behaviors can be targeted in the same way that self-harm or substance use are targeted in specialized psychotherapies for BPD.
Unfortunately, the literature provides limited guidance on management of all cases of comorbidity. Careful diagnosis of BPD and comorbid disorders is the first step. Generally, the course of comorbidities is closely tied with the course of BPD, and thus improvements occur over time and specialized psychotherapy for BPD usually leads to improvements in comorbid disorders.
Most evidence indicates that symptoms of depression remit after specialized treatment for BPD, and the course of anxiety disorder is likely similar. Elements of substance use disorders and some eating disorders may be manifestations of impulsivity in BPD, which also would benefit from specialized DBT treatments, although the prognosis is more guarded in these cases. In general, specialized treatments for BPD are likely to improve both the symptoms of BPD and the comorbid disorders.