Borderline personality disorder is diagnosed by a licensed mental health professional after a careful conversation, not a single test. Knowing what to expect can make the first steps easier.
A licensed mental health professional can diagnose borderline personality disorder after a thorough discussion of symptoms and of personal and family history, including any history of mental illness. A medical exam can help rule out other causes.
National Institute of Mental Health · Borderline personality disorder (brochure)
A diagnosis is not based on one sign or symptom. It is best made after a full clinical interview, which may include talking with previous clinicians, reviewing earlier evaluations, and, when appropriate, talking with friends and family.
National Alliance on Mental Illness · Borderline personality disorder
The American Psychiatric Association (APA) recommends that a first assessment cover why you are seeking help, your goals and preferences for treatment, your symptoms and any other conditions, past treatment, physical health, social and cultural factors, and the risk of suicide, self-injury, or aggression.
The APA suggests that the first evaluation include a questionnaire or rating scale to measure symptoms and how much they affect daily life, so changes can be tracked during treatment.
Borderline personality disorder is usually diagnosed in late adolescence or early adulthood. Occasionally, someone younger than 18 is diagnosed if symptoms are severe and have lasted at least a year.
National Institute of Mental Health · Borderline personality disorder (brochure)
The APA recommends a shared conversation about the diagnosis and treatment, including education about the disorder. Guidance from England asks clinicians to explore treatment in an atmosphere of hope and to explain that recovery is possible.
Guidance from England says people with borderline personality disorder should not be excluded from any health or social care service because of their diagnosis or because they have self-harmed.
Guidance from England suggests a primary care clinician consider referring someone for a borderline personality disorder assessment if they have repeatedly self-harmed, shown persistent risk-taking behavior, or marked emotional instability.
Co-occurring conditions
Borderline personality disorder often occurs alongside other conditions, including depression, bipolar disorder, post-traumatic stress disorder (PTSD), anxiety disorders, substance use disorders, eating disorders, attention-deficit/hyperactivity disorder (ADHD), and conduct problems, as well as physical conditions such as diabetes and obesity. Overlapping symptoms can make diagnosis and treatment harder.
National Institute of Mental Health · Borderline personality disorder (brochure)
Share who also had each kind of condition, from the National Comorbidity Survey Replication (2001 to 2003).
National Institute of Mental Health · Personality disorders statistics
Impulsive behavior can happen in both borderline personality disorder and bipolar disorder. The symptoms of borderline personality disorder occur without the clearly elevated mood of manic or hypomanic episodes, which are a key feature of bipolar disorder.
National Institute of Mental Health · Borderline personality disorder (brochure)
Most people diagnosed with borderline personality disorder are women, but a national survey found that sex was not linked to how common the disorder is. Men may be misdiagnosed with PTSD or depression instead.
