Diagnosing borderline personality disorder (BPD) is a daunting task—so much so that we sometimes defer or ignore the diagnosis. BPD is common, however, occurring in 10% of psychiatric outpatients and 20% of inpatients, and missing it can delay effective treatment (Biskin RS, Can J Psychiatry 2015;60(7):303–308). In this article, I will break down how to identify BPD and offer therapeutic strategies.

Categorical approach

The symptoms that patients with BPD present with rarely align with the DSM-5 criteria. Rather, their complaints take after major depression, bipolar disorder, generalized anxiety disorder, etc. Of course, these disorders are not mutually exclusive and may be comorbid with BPD. Focusing on them, however, can interfere with picking up on the full story and establishing a path toward ­recovery.

A BPD diagnosis requires at least five of nine DSM-5 criteria, which fall into four categories: unstable emotions, impulsive behaviors, inaccurate perceptions, and unsteady relationships (see the table “BPD DSM-5 Criteria and Questions to Ask”). These categories are interrelated. For example, unsteady relationships can trigger unstable emotions, and vice versa.

When assessing for BPD, a good starting place is to ask about affective instability that lasts minutes to hours. In Mark Zimmerman’s research, this stood out as a core feature of the disorder. His team evaluated 3,674 patients and found that asking about affective instability was 92.8% sensitive and had a 99% negative predictive value. This suggests that further investigation of the BPD criteria is warranted if your patient has affective instability (Zimmerman M et al, J Clin Psych 2019;80(1):18m12257). 

Assessing the DSM-5 criteria for BPD can be done in less than 10 minutes. For patients who are squeamish about diagnostic labels, review the criteria before naming the disorder. The DSM’s categorical approach is useful but incomplete, as it does not identify patient strengths or shed light on what happens intrapsychically. 

Dimensional approach

The dimensional approach was born out of psychoanalysis and regards personality as existing on a spectrum from more neurotic to psychotic, with borderline in the middle. At any time, people can move across this spectrum. However, most of the time, their patterns of thinking, feeling, and behaving exist in a particular zone. 

Patients in the borderline zone have intact reality testing much of the time. With stress, however, their reality testing becomes compromised and presents as paranoia, dissociation, or even illusions. Splitting is a common defense mechanism in BPD. Patients tend to idealize or devalue themselves and others, and their sense of self and others fluctuates. With adequate support and structure, however, their relationships can appear to thrive. A patient’s ability to adapt in this manner can help differentiate BPD from psychosis or mania. 

To get a sense of where your patient falls dimensionally, here are a couple of useful questions: 

• “Can you tell me about yourself so I can get a real picture of you as a person?”
• “Can you describe someone close to you so I can get a full sense of who they are?”

Pay attention to how detailed, multilayered, and relatable the patients’ responses are. Patients with BPD often give answers that are vague, inconsistent, or exaggerated with caricatures of heroes and villains (Yeomans F et al. Transference-Focused Psychotherapy for Borderline Personality Disorder: A Clinical Guide. Washington, DC: American Psychiatric Publishing; 2015:83–98).

Other considerations

Rating scales

Self-rating screens help us know when to probe further for BPD and track a patient’s course. These screens cast a wide net, so interpret them with caution. A positive screen does not mean your patient has BPD, but a negative screen does a pretty good job of ruling it out.

Comorbidity

Comorbidity can also indicate when to look for BPD. In another study by Zimmerman and colleagues, BPD was common in patients presenting for bipolar disorder, posttraumatic stress disorder, panic disorder with agoraphobia, and major depressive disorder. BPD was found in 33.8% of patients with bipolar I (odds ratio [OR] 4.52; 95% confidence interval [CI] 2.7–7.5) and in 27.1% with bipolar II (OR 3.28; 95% CI 2.1–5.2; Zimmerman M et al, Ann Clin Psychiatry 2017;29(1):54–60).

Gender

BPD is wrongly stereotyped as a female disorder. The rates are similar across genders, though the presentations differ (Grant J et al, J Clin Psych 2008;69(4):533–534). Men present more often with anger, substance use, and difficulty engaging in treatment, while women are more likely to have emotional instability, identity diffusion, and self-harm (Bayes A and Parker G, Psychiatry Res 2017;257:197–202). 

Countertransference

Take stock of your thoughts and feelings about the patient. Reactions to BPD may include frustration, hatred, guilt, anxiety, helplessness, and rescue fantasies. These feelings commonly vacillate and vary ­considerably. 

Genetics

Ask about family history and temperament. A Swedish population-based study estimated the heritability of BPD at 46% (95% CI 39%–53%; Skoglund C, Mol Psychiatry 2021;26(3):999–1008). Intense emotionality early in life has been implicated as a risk factor (Stepp S et al, BPD Emot Dysregul 2014;1:18). 

Communicating the diagnosis

After you review the diagnostic steps above, it is time to share your formulation. By and large, this goes well, especially when you use familiar terms, connect your impressions with details of the patient’s history, and recognize their strengths.

If the patient struggles with the diagnosis, hedge your bets. Let them know you believe BPD applies, but do not force it. With more time, education, patience, and persistence, they can come around. When done collaboratively, this diagnostic process fosters an alliance around a shared understanding of your patient’s struggles. It reduces their sense of isolation and anchors the hope of recovery to a rational plan of treatment. BPD is not a life sentence. Two-thirds of cases eventually achieve remission or recovery (Stone MH, Psychodyn Psych 2016;44(3):449–474).

Carlat Verdict 

Recognizing BPD paves the way to effective treatment. When the diagnosis is explained in a personalized, collaborative way, your patient will feel understood, possibly for the first time.