Updated: Nov 21, 2019
These are two very different disorders that present very similarly. My official diagnosis is Bipolar Disorder II however, my psychiatrist also feels that I fit a lot of the criteria for Borderline Personality Disorder (also known as Emotionally Unstable Personality Disorder). Because of this, I am actually being treated for both.
The main difference between Bipolar Disorder and Borderline Personality Disorder is that Bipolar Disorder is a mood disorder and therefore is primarily treated with medication however, Borderline Personality Disorder (BPD) is a personality disorder and is therefore treated mainly with psychological therapies.
Both Bipolar Disorder and BPD present with extreme mood swings (from depressive to manic states) and an inability to regulate emotions. However, typically in people with Bipolar Disorder mood swings last for a significant period of time, from weeks to even months, where as people with borderline personality disorder mood swings can occur multiple times throughout the day.
BPD has a large basis within relationships and therefore gets a very bad reputation. It can be difficult for someone with BPD, and also difficult for the person in a relationship with someone with BPD. Typically people with BPD are insecure in their relationships due to a combination of chronic emptiness and also experience a fear of abandonment, this can lead people to either become clingy and overly attached or to isolate and push people away. Part of the symptoms of BPD is difficulty regulating emotions which can lead a person with BPD to have extremely strong outburst of emotion like anger to which they may not be able to regulate their response, this is why BPD is also known and Emotionally Unstable Personality Disorder. BPD/EUPD means that often the person feels all of their emotions much more intensely than someone else and this can lead to the drastic mood swings which are often mistaken for Bipolar Disorder. There are also a range of other symptoms that a person with BPD might experience for example paranoia and dissociation.
Bipolar Disorder is a mood disorder and therefore it's main symptoms are to do with mood, this is why it's main treatment is often medication. In Bipolar Disorder someone will experience a long period of depression where they will often feel low, lethargic and worthless, these periods can often last between 2 weeks to a number of months. To be diagnosed with Bipolar Disorder a person also has to of experienced at least one form of mania, this could be mania or hypomania. Hypomania is when a person may feel very energetic, have racing thoughts, and feel very euphoric. Full blown mania is all of these symptoms but they may cause the person to get themselves in trouble and the symptoms are to the extent that the person cannot continue with their everyday life.
Although Bipolar Disorder and BPD have many symptoms and behaviour in common, they are actually very different disorders that require very different treatment and therefore it's very important that people get the right diagnosis. However, unfortunately people with Bipolar Disorder or BPD are very often misdiagnosed. Often this is because doctors are reluctant to diagnose personality disorders due to the fact that there is a stigma that they are untreatable. Conversely, doctors are also reluctant to diagnose Bipolar Disorder as it is a life long disorder that cannot be cured and is not always treatable with therapy.