The DSM-5 criteria for borderline personality disorder are listed in Box 1.18 Although the DSM-5 requires any five of these nine criteria in order to make a diagnosis, even low levels of borderline pathology (e.g. one criterion) are associated with substantial increases in psychosocial impairment.19
Box 1 Diagnostic criteria for borderline personality disorder18
A pervasive pattern of instability of interpersonal relationships, self-image, and affects, and marked impulsivity, beginning by early adulthood and present in a variety of contexts, as indicated by five (or more) of the following:
- Frantic efforts to avoid real or imagined abandonment (do not include suicidal or self-mutilating behaviour covered in criterion 5)
- A pattern of unstable and intense interpersonal relationships characterised by alternating between extremes of idealisation and devaluation
- Identity disturbance: markedly and persistently unstable self-image or sense of self
- Impulsivity in at least two areas that are potentially self-damaging (e.g. spending, sex, substance abuse, reckless driving, binge eating – do not include suicidal or self-mutilating behaviour covered in criterion 5)
- Recurrent suicidal behaviour, gestures, or threats, or self-mutilating behaviour
- Affective instability due to a marked reactivity of mood (e.g. intense episodic dysphoria, irritability, or anxiety usually lasting a few hours and only rarely more than a few days)
- Chronic feelings of emptiness
- Inappropriate, intense anger or difficulty controlling anger (e.g. frequent displays of temper, constant anger, recurrent physical fights)
- Transient, stress-related paranoid ideation or severe dissociative symptoms
Despite the evidence of the reliability and validity of the diagnosis, and the treatability of the condition,20 many people with borderline personality disorder remain undiagnosed in clinical practice. This places them at risk of being given treatments that are ineffective or even harmful.21 The central task for diagnosing personality disorder is to separate ‘state’ (transient aberrations in mental state) from ‘trait’ (long-standing patterns of thinking, feeling, behaving, perceiving and relating). Many mental state disorders can present with features that are similar to borderline personality disorder. For example, affective dysregulation is characteristic of both bipolar disorder and borderline personality disorder. Also, the current definition of depression incorporates non-specific forms of dysphoria that overlap with borderline personality disorder. What distinguishes borderline personality from these other disorders is that the features are present most of the time and comprise part of the patient’s ‘usual self’. These patients will tell you that this is how they ‘usually are’. Although various tools are available to aid the diagnosis of borderline personality disorder, clinical application of the DSM-5 criteria is sufficient in a busy clinical practice. Each of the nine criteria should be enquired about and considered in turn.
A common cause of misdiagnosis of borderline personality disorder is to rely on ‘gut feeling’ when a patient presents as interpersonally abrasive, sullen or hostile, particularly if the individual also engages in self-harm. Such diagnoses are often unreliable because they do not assess each of the DSM-5 borderline personality disorder criteria and do not take into account other reasons for such presentations, such as temporary aberrations in mental state, depression or other disorders.
Another cause of diagnostic confusion is the high rate of comorbid conditions. Comorbidity with other personality disorders and with mental state disorders is the norm. At times, these other disorders (e.g. mood, anxiety, eating and substance use disorders) can overwhelm the clinical picture, but this does not indicate that the underlying personality pathology is unimportant or should be a secondary concern.21 Rather, there is evidence to suggest that personality disorder might be a key vulnerability factor for recurrent mental state disorders.22,23 Patients with borderline personality disorder who have these co-occurring conditions should be treated for these conditions in accordance with best practice. However, there should not be a disproportionate emphasis given to the immediate relief of mental state pathology at the expense of managing the borderline personality disorder.