This patient has borderline personality disorder (BPD). Features of BPD include interpersonal hypersensitivity (for example, intense and unstable relationships and intense efforts to avoid abandonment), difficulty controlling emotions such as anger, impulsive or destructive behavior (for example, spending money or promiscuous sex), recurrent suicidal gestures, and unstable self-image. BPD can be misdiagnosed as depression or bipolar disorder. About 6% of primary care patients have BPD. The mainstay of treatment for BPD is psychotherapy. Pharmacologic treatment of BPD is adjunctive to psychotherapy. There are no FDA-approved medications for personality disorders; medications are used to relieve symptoms (for example, mood stabilizers for mood swings and impulsivity).

Patients with bipolar disorder report different neurovegetative symptoms than patients with BPD, such as a decreased need for sleep and waking with increased energy; they report an increase in activities but may move from one thing to another without completing tasks and may become more social or hypersexual but without indication of interpersonal loss. The patient's speech is often loud and full of jokes and puns, and he or she may be distractible, responding to irrelevant stimuli. Patients with BPD tend to behave angrily, impulsively, or self-destructively in the context of real or perceived interpersonal loss, whereas no such pattern is apparent in those with bipolar disorder.

Depressed mood, anhedonia, lack of motivation, lack of energy or mood reactivity, overeating, and oversleeping are typical characteristics of a depressive disorder. BPD depressions are often characterized by feelings of emptiness; patients' mood often improves after being reunited with a “lost” partner or finding a new loved one.

Generalized anxiety disorder (GAD) is characterized by excessive anxiety and worry about various events or activities on most days for at least 6 months, with difficulty controlling worrying. Associated symptoms include fatigue, irritability, restlessness, insomnia, and difficulty concentrating. Such patients often have comorbid anxiety disorders, depression, or substance abuse. Patients with GAD often have somatoform symptoms, which can make them high utilizers of health care resources. This patient does not exhibit any of these symptoms, making this diagnosis unlikely.