Borderline Personality Disorder and Bipolar Disorder: What’s the Difference?

Getting the right diagnosis often isn’t easy for psychiatric conditions. In our field, we don’t yet have biologic tests that can easily define one condition from another. If your blood pressure is 140 over 90, you have hypertension or high blood pressure. In mental health, we have to rely on a description of patterns or symptoms to makes diagnoses. This model is fraught with challenges.

Without a clear biological model to work from, and given the complexity of the human brain, the field has settled upon dividing these descriptions of symptoms into syndromes. The Diagnostic and Statistical Manual of Mental Disorders (DSM) holds these symptom descriptions in order to help professionals make reliable and consistent diagnoses. This means a social worker in Detroit should make the same diagnosis as a psychiatrist in Boston and a psychologist in Santa Fe.

However, the diagnostic process is more complex than just reading symptoms in a DSM. Here are a few thoughts on what I have observed in making diagnoses:

• Diagnosis is best viewed as a movie, not a snapshot. In a snapshot, people with different diagnoses can appear to have similar symptoms. The key is to step back and develop a view of their history and the pattern of symptoms.
• People may present different symptoms over time, which can change their diagnosis. A person who has a depressive disorder, for example, could have a manic episode a year later. This would change that person’s diagnosis to bipolar disorder. The original diagnosis wasn’t a misdiagnosis—rather the movie changed its storyline and the diagnosis needed to change as well.
• It’s common to have more than one diagnosis. For many people, there may not be one simple diagnosis. For example, people can have both bipolar disorder and a substance use disorder diagnoses.
• Medical problems or medications can influence or even mimic symptoms. Hypothyroidism presents with almost all symptoms of depression for example, and steroids can add risk for mood symptoms.
• Get informed. Patients who know their symptoms can help in the search for a diagnosis. People have brought write-ups to their appointment as they search for answers, and I have referred some people to the DSM-5 so they can evaluate their experience.

Let’s focus on the sometimes-confused conditions of Bipolar Disorder and Borderline Personality Disorder (BPD). In a snapshot, they can look similar—both can present with impulsive behavior, intense emotions and suicidal thinking. But this snapshot is not the best way to tell them apart. It’s really the movie of the symptom presentation over time that can help make the diagnosis distinct.

Classic Bipolar Disorder Type 1 is easier to differentiate from BPD than Bipolar 2. True manic symptoms (often with hallucinations) are the hallmark of Type 1 and these symptoms are not seen in the same way in BPD. Bipolar Type 2 is a more challenging diagnosis to differentiate from BPD, because the classic manic episode is absent. So, on the surface, it can appear more like BPD. Here are a few ways to help tell the difference between bipolar and BPD:

How Often Do Moods Change?

People with Bipolar Type 1 have cycles that switch from a depressive state to a manic state. Manic symptoms sometimes include flashes of deep depression within the manic episode (called rapid cycling). Between cycles, people often have periods of true symptom-free wellness. This period of wellness can last weeks, months or years depending on the person. People diagnosed with BPD typically have more persistent day-to-day emotional symptoms which can impact everyday life. BPD mood changes are more persistent, short-lived and reactive to environmental factors, like stress at work or home.

Is Sleep Normal?

Sleep changes are often an early indicator of a bipolar disorder. During a bipolar episode, a person might be awake for days and not experience fatigue or they may sleep for days. Meanwhile, sleep patterns are less commonly impacted in BPD.

Is There a Family History?

Mood disorders, like bipolar disorder and depression, run in families, but aren’t directly passed on through a single, specific gene. A family history of mood disorders increases the chances of mood disorders appearing in relatives.

Are Relationships Often Unstable?

Intense relationships often fraught with conflict are the hallmark of borderline personality disorder. People with BPD often have intense relationship histories, and many of their experiences with emotional dysregulation (intense reactions and variabilities) are in response to relationship interactions.

Is Self-Harm a Symptom?

Self-harm such as cutting one’s skin is more common in BPD and is thought to be a way to help with emotional regulation. “I’m not suicidal, I was just trying to change my feelings by cutting,” I’ve been told by individuals with BPD. In fact, 75% of individuals with BPD have cut, burned, hit or injured themselves.

Diagnosing a mental illness isn’t like diagnosing some physical illnesses—it takes a lot of observation and understanding to find the right diagnosis. If your diagnosis doesn’t feel right or isn’t clear, it’s best to talk to your clinician. Ask about your diagnosis and treatment plan and be engaged in the diagnostic process. If you and your practitioner aren’t sure, ask for a second opinion. It’s okay not to be sure, and it’s smart to keep learning.

Both BPD and bipolar have good treatment options, but they are very different options, so putting time into getting a correct diagnosis is essential. These are serious health conditions that need individualized support and care in order to optimize recovery.

Ken Duckworth is medical director at NAMI.