Importance of Longitudinal Assessments in a Case of Comorbid Polysubstance Use Disorder and Borderline Personality Disorder Misdiagnosed As Bipolar I Disorder

Differentiating between borderline personality disorder (BPD) and bipolar disorder (BD) can be difficult. Both may present with altered mood states, deliberate self-harm, suicidality, impulsivity, unstable relationships, and risky behaviors. A manic episode is characterized by at least one week of elevated or irritated mood and at least three of the following: distractibility, impulsivity, grandiosity, flight of ideas, psychomotor activity, decreased need for sleep, and pressured speech. Borderline personality disorder is characterized by unstable mood and relationships, fear of abandonment, impulsivity, self-mutilation, suicidality, and a feeling of emptiness. In combination with polysubstance use, borderline personality disorder can present similarly to a manic episode and lead to an incorrect diagnosis of bipolar I disorder. In this study, we present a 44-year-old female whose psychiatric history highlights the importance of long-term patient observation in making an accurate diagnosis. Over the course of several years, she was given incorrect psychiatric diagnoses, including attention deficit hyperactivity disorder (ADHD), generalized anxiety disorder, and bipolar I disorder. As a result, her interpersonal relationships remained unstable and significantly affected her quality of life. Over the course of consistent, long-term psychiatric appointments, conversations with family members, and notes from previous psychiatrists, it became evident that substance use had also complicated her psychiatric history, leading to the aforementioned diagnoses. Once this was established, she was diagnosed with borderline personality disorder; subsequent correct medical intervention has been integral in helping her maintain a steady job and improve her interpersonal relationships and quality of life.