Table 4.

Key knowledge gaps and research questions for future studies in BPD.

Subject	Knowledge gap	Research questions
Causality	98% of studies are observational (causality not investigated)	What is the nature of the relationship between dissociation and associated BPD outcomes (BPD severity, psychotherapy response, etc.)?
Dissociation type	Studies did not distinguish between dissociation subtypes phenomenologically	Do primary, secondary and tertiary dissociation subtypes have different impacts on BPD outcomes? Is state or trait dissociation more important to treatment efficacy? Are there specific dissociative phenomena that impact outcomes more than others (e.g., hostile dissociative voices, dissociative amnesia)?
Impact of assessing dissociation in BPD	Limited attention on dissociation assessment for BPD in clinical practice	Can assessment of dissociation lead to useful information about treatment outcomes, risk factors for self-harm or suicidality, or need for particular treatments? Does tracking dissociative symptoms provide useful clinical information? What measures are most appropriate?
BPD diagnosis	Significant overlap between BPD, PTSD and DDs. Studies often do not account for possible comorbidities	Can assessment measures accurately differentiate between DDs, PTSD and BPD?
Substance abuse	Association between dissociation and sedative substance	Can this finding be replicated? What are the potential mechanisms? Can treatment of dissociation reduce sedative or alcohol misuse?
Sex, gender and gender identity	No studies addressing the role of gender or gender identity 90% of participants female	Are certain dissociative symptom subtypes more prevalent in certain sexes or genders? Is there a relationship between dissociation severity and gender identity? Are there sex or gender differences in the outcomes associated with dissociation?
Demographics	80% of studies were in Germany or USA	Are there differences in how dissociation presents in BPD populations across cultures?
Self-harm	Some BPD patients use self-harm to manage dissociation	Do certain subtypes of dissociation, or dissociation severity, have different implications for self-harm?
Suicidality	Few studies; mixed results	Do dissociative symptoms impact suicidality? Do specific subtypes of dissociative symptoms have different impacts on suicidality?
Cognitive function	Dissociation is associated with a range of memory and cognitive deficits	Are the deficits caused by dissociation? Which BPD patients are vulnerable to dissociation impacting cognitive assessments?
Psychotherapy	Dissociative symptoms are associated with poorer psychotherapy outcomes	Would dissociation specific treatments improve BPD outcomes?
Pharmacology	Research indicates reduced pain perception and altered threshold, and potential role of the opioid system	Would naloxone or other opioid antagonists improve dissociation related outcomes in BPD?
Physiologic state	Dissociation associated with increased cBMI and reduced water intake	What is the mechanism of these findings? Is dissociation associated with alterations of other drives, such as psychomotor activity, sexual behaviors, or maternal behaviors in BPD?

BPD: Borderline Personality Disorder; PTSD: Posttraumatic Stress Disorder.