Many aspects of psychotherapy in the treatment of borderline personality disorder require further investigation. For example, further controlled treatment studies of psychodynamic psychotherapy, dialectical behavior therapy, and other forms of cognitive behavior therapy are needed, particularly in outpatient settings. In addition, psychotherapeutic interventions that have received less investigation, such as group therapy, couples therapy, and family interventions, require study. The following are some specific questions that need to be addressed by future research:

• What is the relative efficacy of different psychotherapeutic approaches? Which types of patients respond to which types of psychotherapy?
• What components of dialectical behavior therapy and psychodynamic psychotherapy are responsible for their efficacy? What common elements of these treatments are responsible for their efficacy?
• What are the indications for use of psychodynamic psychotherapy and dialectical behavior therapy? How does the presence of certain clinical features (e.g., prominent self-destructive behavior or dissociative features) affect response to these treatments?
• To what extent is a good outcome due to the unique components of these treatments versus the amount of treatment received?
• How effective are psychodynamic psychotherapy and dialectical behavior therapy when used in the community rather than in specialized treatment settings, and how can these treatments be optimally implemented in community settings?
• What is the optimal duration of psychotherapy for patients with borderline personality disorder?
• Is there a model of brief psychotherapy (12–30 sessions) that is effective for borderline personality disorder?
• What are the optimal frequencies of psychotherapeutic contact for different psychotherapies during different stages of treatment?
• What is the relative efficacy of psychotherapy versus pharmacotherapy for patients with borderline personality disorder? Do certain patients respond better to one treatment modality than to the other?
• What is the relative efficacy of a combination of psychotherapy and pharmacotherapy versus either treatment modality alone?

Many aspects of pharmacotherapy in the treatment of borderline personality disorder also require investigation. Further controlled treatment studies of medications—in particular, those that have received relatively little investigation (for example, atypical neuroleptics)—are needed. Studies of continuation and maintenance treatment as well as treatment discontinuation are especially needed, as are systematic studies of treatment sequences and algorithms. The following are some specific questions that need to be addressed by future research:

• What is the relative efficacy of different pharmacological approaches for the behavioral dimensions of borderline personality disorder?
• What is the relative efficacy of different pharmacological augmentation and combination strategies, and what is their efficacy compared with treatment with single agents?
• How does the presence of certain clinical features (for example, prominent self-destructive behavior or dissociative features) affect response to pharmacotherapy?
• What is the minimal dose and duration of an adequate trial for different medications in patients with borderline personality disorder?
• What is the optimal duration of different types of medication treatment?
• What are the indications for discontinuation of effective pharmacological treatment?
• Are atypical neuroleptics or typical neuroleptics more effective or better tolerated in patients with borderline personality disorder?
• How efficacious are mood stabilizers for patients with borderline personality disorder, and which patients are most likely to benefit from this treatment? Are certain mood stabilizers more effective than others?
• What role should ECT have in the treatment of patients with refractory or severe borderline personality disorder?