One of the most common mistakes people make about mental illnesses is assuming that bipolar disorder and borderline personality disorder (BPD) are the same. There is so much nuance and definitional ambiguity in mental health sometimes that confusion can be totally understandable, but by the end of this article, hopefully the difference between bipolar disorder and BPD will be clear!
The National Institute of Mental Health defines bipolar disorder as a lifelong “brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks.” Bipolar disorder is also known as manic-depressive illness, and consists of episodes of mania (or hypomania) and depression. Manic and hypomanic episodes typically see emotional highs (such as feeling like one is at the top of the world, being unusually productive and energetic, and engaging in risky behavior like sudden excessive spending or reckless sex), while depressive episodes can cause one to lose all energy and productivity, feel incapable and empty, eat/sleep too much or too little, and/or even engage in suicidal thinking/action.
These episodes and symptoms manifest in different ways for different people, but generally can be described as one of four types of bipolar disorder (yes, bipolar disorder is just a broader term, and people are diagnosed with more specific illnesses!):
Bipolar I Disorder
This is usually what people think of when they hear “bipolar disorder.” Those with Bipolar I experience manic episodes lasting at least a week (or, if shorter, extremely severe manic episodes) and depressive episodes lasting at least two weeks. It is also possible for high and low symptoms to exist within one “episode"--for the symptoms to "mix."
Bipolar II Disorder
Similar to Bipolar I Disorder, except people with Bipolar II experience hypomanic episodes, a less severe version of manic episodes, instead of manic episodes.
Cyclothymic Disorder (cyclothymia)
Characterized by a continuous pattern of hypomanic and depressive symptoms for at least two years (one year for children and adolescents) without meeting the diagnostic requirements to have such symptoms named hypomanic and depressive episodes.
There may be other specific cases where symptoms of bipolar disorder emerge, but which do not meet the definitions of the three cases above. These require special diagnoses.
Borderline personality disorder (BPD), on the other hand, is defined by the National Institute of Mental Health as “a serious mental disorder marked by a pattern of ongoing instability in moods, behavior, self-image, and functioning.” Like bipolar disorder, people with BPD also experience severe mood swings that may lead to reckless behavior and even suicide. However, unlike bipolar disorder, wherein there are defined manic/hypomanic and depressive episodes, BPD consists of drastic swings in not only mood and behavior but also in all aspects of the individual's life, often times undergoing such chaotic spectrums in the span of just a few hours to days. BPD can severely cripple relationships the person has with others around them, and can lead to unstable, intense emotions that induce a high risk of self-harm and suicide.
Most mental health professionals agree that BPD is a misnomer, and BPD can in fact be often misdiagnosed or underdiagnosed because many of its symptoms overlap with other mental illnesses.
Mental illnesses are almost never caused by one single factor alone, but certain situations can increase the risk of mental illness.
Both bipolar disorder and BPD are more likely to manifest in those whose family member(s) have such disorders, and in fact, BPD is five times more likely to occur in someone whose first-degree biological relative(s) have BPD.
The two's differences begin to emerge more clearly when looking at other potential causes. For example: scientists aren’t yet sure of the exact links between bipolar disorder and abnormal brain structures, whereas there is clearer evidence supporting the idea that BPD leads to “structural and functional changes in the brain, especially in the areas that control impulses and emotional regulation.” Nonetheless, a change in brain structure and/or functioning cannot be used as clear-cut proof for someone having bipolar disorder or BPD since much research remains to be done.
In addition, people with BPD seem to have a higher chance of having experienced some sort of trauma in their life, especially during childhood. Abuse, abandonment, wildly unstable relationships, and hostile conflicts can all increase one’s risk of BPD. However, trauma is not a requirement for BPD, and not all people with BPD have experienced prior trauma.
While both bipolar disorder and BPD can be treated with psychotherapy