Core features of BPD, such as mood lability, impulsivity, and risk-taking behaviors, are also part of the diagnostic criteria for BD (Table 2).1 Similarly, depressive symptoms prevail in the course of BD.17,18 This adds complexity to the differential because “depressivity” is also part of the diagnostic criteria for BPD.1 Therefore, comprehensive psychiatric assessments and longitudinal observations are critical to diagnostic accuracy and treatment planning. Further characterization of symptoms, such as onset patterns, clinical course, phenomenology of symptoms (eg, timing, frequency, duration, triggers), and personality traits, will provide information to properly distinguish these 2 syndromes when, for example, it is unclear if the “mood swings” and impulsivity are part of a mood or a personality disorder (Table 3).
Clinical features: A closer look
Borderline personality disorder. Affect dysregulation, emotional instability, impoverished and unstable self-image, and chronic feelings of emptiness are core features of BPD.1,5,19 These characteristics, when combined with a fear of abandonment or rejection, a compromised ability to recognize the feelings and needs of others, and extremes of idealization-devaluation, tend to culminate in problematic and chaotic relationships.6,19 Individuals with BPD may become suspicious or paranoid under stressful situations. Under these circumstances, individuals with BPD may also experience depersonalization and other dissociative symptoms.6,20 The mood lability and emotional instability observed in patients with BPD usually are in response to environmental factors, and although generally intense and out of proportion, they tend to be ephemeral and short-lived, typically lasting a few hours.1,5 The anxiety and depressive symptoms reported by patients with BPD frequently are associated with feelings of “falling apart” or “losing control,” pessimism, shame, and low self-esteem. Coping strategies tend to be poorly developed and/or maladaptive, and individuals with BPD usually display a hostile and antagonistic demeanor and engage in suicidal or nonsuicidal self-injury (NSSI) behaviors as means to alleviate overwhelming emotional distress. Impulsivity, disinhibition, poor tolerance to frustration, and risk-taking behaviors are also characteristic of BPD.1,5 As a result, BPD is usually associated with significant impairment in functioning, multiple hospitalizations, and high rates of comorbid mood disorders, posttraumatic stress disorder (PTSD), SUDs, and death by suicide.
Bipolar disorder. Conversely, the fluctuations in mood and affect observed in patients with BD are usually episodic rather than pervasive, and tend to last longer (typically days to weeks) compared with the transient mood shifts observed in patients with BPD.4,17,18 The impulsivity, psychomotor agitation, and increased goal-directed activity reported by patients with BD are usually seen in the context of an acute affective episode, and are far less common during periods of stability or euthymic affect.4,17,18 Grandiosity and inflated self-esteem—hallmarks of a manic or hypomanic state—seem to oppose the unstable self-image observed in BPD, although indecisiveness and low self-worth may be observed in individuals with BD during depressive episodes. Antidepressant-induced mania or hypomania, atypical depressive episodes, and disruptions in sleep and circadian rhythms may be predictors of BD.4,21 Furthermore, although psychosocial stressors may be associated with acute affective episodes in early stages of bipolar illness, over time minimal stressors are necessary to ignite new affective episodes.22,23 Although BD is associated with high rates of suicide, suicide attempts are usually seen in the context of an acute depressive episode, and NSSI behaviors are less common among patients with BD.24
Lastly, other biographical data, such as a history of early life trauma, comorbidity, and a family history of psychiatric illnesses, can be particularly helpful in establishing the differential diagnosis between BD and BPD.25 For instance, evidence suggests that the heritability of BD may be as high as 70%, which usually translates into an extensive family history of bipolar and related disorders.26 In addition, studies suggest a high co-occurrence of anxiety disorders, attention-deficit/hyperactivity disorder, and SUDs in patients with BD, whereas PTSD, SUDs, and eating disorders tend to be highly comorbid with BPD.27 Childhood adversity (ie, a history of physical, sexual, or emotional abuse, or neglect) seems to be pivotal in the genesis of BPD and may predispose these individuals to psychotic and dissociative symptoms, particularly those with a history of sexual abuse, while playing a more secondary role in BD.28-31
Implications of misdiagnosis
In the view of the limitations of the existing models, multidimensional approaches are necessary to improve diagnostic accuracy. Presently, the differential diagnosis of BD and BPD continues to rely on clinical findings and syndromic classifications. Misdiagnosing BD and BPD has adverse therapeutic and prognostic implications.32 For instance, while psychotropic medications and neuromodulatory therapies (eg, electroconvulsive therapy, repetitive transcranial magnetic stimulation) are considered first-line treatments for patients with BD, psychosocial interventions tend to be adjunctive treatments in BD.33 Conversely, although pharmacotherapy might be helpful for patients with BPD, psychosocial and behavioral interventions are the mainstay treatment for this disorder, with the strongest evidence supporting cognitive-behavioral therapy, dialectical behavioral therapy, mentalization-based therapy, and transference-focused therapy.34-36 Thus, misdiagnosing BD as BPD with comorbid depression may result in the use of antidepressants, which can be detrimental in BD. Antidepressant treatment of BD, particularly as monotherapy, has been associated with manic or hypomanic switch, mixed states, and frequent cycling.21 Moreover, delays in diagnosis and proper treatment of BD may result in protracted mood symptoms, prolonged affective episodes, higher rates of disability, functional impairment, and overall worse clinical outcomes.24 In addition, because behavioral and psychosocial interventions are usually adjunctive therapies rather than first-line interventions for patients with BD, misdiagnosing BPD as BD may ultimately prevent these individuals from receiving proper treatment, likely resulting in more severe functional impairment, multiple hospitalizations, self-inflicted injuries, and suicide attempts, since psychotropic medications are not particularly effective for improving self-efficacy and coping strategies, nor for correcting cognitive distortions, particularly in self-image, and pathological personality traits, all of which are critical aspects of BPD treatment.
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