What personality disorder is characterized by long-standing difficulties in relationships, emotional dysregulation, marked impulsivity, and intolerance of being alone in an adult patient?

Borderline Personality Disorder

The clinical presentation described—long-standing difficulties in relationships, emotional dysregulation, marked impulsivity, and intolerance of being alone—is characteristic of Borderline Personality Disorder (BPD). 1

Diagnostic Features

BPD is defined by a pervasive pattern of instability in interpersonal relationships, self-image, and affects, combined with marked impulsivity, with onset in early adulthood. 1 The specific symptoms that match this patient's presentation include:

• Unstable interpersonal relationships that alternate between idealization and devaluation (denigration), rather than maintaining balanced perceptions of others over time 1, 2
• Emotional dysregulation manifesting as rapid mood shifts from depression, anxiety, and rage to euthymia, often lasting minutes to hours 1
• Marked impulsivity in areas that are potentially self-damaging, such as excessive spending, impulsive sexual activity, or dangerous driving 1
• Frantic efforts to avoid real or imagined abandonment, which explains the intolerance of being alone 3, 4

Additional Core Features to Assess

Beyond the presenting symptoms, clinicians should specifically inquire about:

• Recurrent suicidal behavior, gestures, or threats, and nonlethal forms of self-injury (present in the majority of BPD patients, with 11-44% having attempted suicide) 1, 2
• Identity disturbance with a markedly unstable self-image that oscillates between grandiosity and worthlessness 1, 2
• Chronic feelings of emptiness 3, 4
• Inappropriate, intense anger or difficulty controlling anger 1
• Transient, stress-related paranoid ideation or severe dissociative symptoms (derealization, depersonalization) 1, 2, 3

Critical Differential Diagnoses

The presence of suicidality and self-harm points definitively toward BPD rather than Histrionic Personality Disorder (HPD), which centers on attention-seeking behavior without self-destructive behaviors. 2 Key distinctions include:

• BPD involves chaotic, unstable relationships marked by genuine fear of abandonment and alternating idealization/devaluation, whereas HPD features superficial emotionality focused on gaining attention 2
• BPD patients exhibit a varying, unstable self-concept that shifts dramatically, which is not characteristic of HPD 2
• Identity disturbance is a key differentiator, with BPD showing profound confusion about self-concept 2

When evaluating rapid mood shifts in adults, consider BPD before diagnosing Bipolar Disorder. 1 The distinction is critical:

• BPD mood shifts are typically brief (minutes to hours), reactive to interpersonal stressors, and represent chronic baseline patterns rather than distinct episodes 1
• Bipolar disorder presents with clearly demarcated phases of mania/hypomania and depression lasting days to weeks, with marked reduction in need for sleep (a pathognomonic sign present in <50% of BPD cases) 1
• BPD dissociative symptoms should not be mistaken for psychotic disorder, as BPD lacks formal thought disorder, disorganized thought, and disorganized speech characteristic of schizophrenia 2

Assessment Approach

Accurate diagnosis requires gathering information from multiple sources using varied developmentally sensitive techniques, as self-reporting may be unreliable. 2 Specifically:

• Conduct semi-structured interviews to systematically assess DSM criteria 3, 4
• Obtain collateral information from family members or close contacts, as there are often discrepancies between patient and informant reports 1, 2
• Perform longitudinal assessment to observe temporal stability of symptoms and relationship patterns over time 2
• Specifically inquire about suicide attempts, self-injury, identity confusion, and dissociative experiences to identify BPD features 2

Common Pitfalls to Avoid

• Never dismiss the diagnostic significance of self-harm and suicidality—these are hallmark features of BPD, not HPD 2
• Do not confuse BPD's transient paranoid ideation or dissociative symptoms with primary psychotic disorder 2
• Avoid prematurely diagnosing Bipolar Disorder in patients with brief, reactive mood shifts without clear manic/hypomanic episodes 1, 5
• Do not overlook the pervasive pattern requirement—symptoms must be long-standing and present across multiple contexts 1

Comorbidity Considerations

Most patients with BPD have coexisting mental disorders: mood disorders (83%), anxiety disorders (85%), substance use disorders (78%), and post-traumatic stress disorder. 3, 4 These comorbidities compound functional impairment and must be assessed and addressed in treatment planning.