Diagnosing psychiatric illness isn't easy. There's usually no lab test, physical indication, or quantitative measurement that can distinguish one illness from another, and often no magic bullet that can ensure effective treatment. Clinicians are dependent on a description of symptoms and patterns over time to make a diagnosis and these often appear similar even when the underlying illness is very different.
One example of this difficulty is in the incidence of borderline personality disorder being misdiagnosed as bipolar disorder. Both are characterized by impulsive behavior, mood swings, and suicidal thinking but have different causes and different treatments. Only an experienced medical professional can make the right diagnosis and determine appropriate treatment, but patients and their families can help by paying attention to their own thoughts and feelings and describing them accurately.
The key difference between bipolar disorder and borderline personality disorder is that bipolar disorder is a mood disorder and borderline personality disorder, as its name implies, is a personality disorder.
Mood disorders are characterized by drastic changes in mood that may come on suddenly or randomly without an apparent trigger. Depression is the most common mood disorder.
Personality disorders are characterized by a long-term pattern of thoughts, feelings, and behaviors that cause distress and problems functioning, particularly in interpersonal relationships and often with strong reactions to conflict or other external events. Paranoia and narcissism are core facets of some personality disorders.
Bipolar disorder, also known as manic depression, causes extreme swings in mood with alternating periods of mania and depression that are unrelated to external events and might last days or weeks. During periods of mania, symptoms might include excessive bursts of physical and/or mental energy, racing thoughts, high levels of happiness or irritability, risky and impulsive behavior, and lack of sleep. Periods of depression are characterized by deep, persistent sadness; low levels of activity and energy; loss of pleasure in previously pleasurable activities; changes in appetite and/or sleep habits; feelings of worthlessness or guilt; and recurrent thoughts of suicide or harming oneself. Between periods of mania and depression, people may have brief or lengthy periods of stability and wellness.
Borderline personality disorder can resemble bipolar disorder in its manifestation of impulsive behavior, mood swings, and thoughts of suicide or self-harm. Where it differs most notably is in the presence of long-term and persistent – rather than cyclical – patterns of chaotic, unstable interpersonal relationships and episodes of mood changes and impulsivity that are often triggered by interpersonal difficulties. People with borderline personality disorder are very sensitive and react intensely and disproportionately to conflict or disappointment. They have difficulty controlling their emotions and react with inappropriate responses, such as an impulse to self-harm. They may make frantic efforts to avoid abandonment, which further destabilizes relationships or leads to clinging to inappropriate relationships.
Bipolar disorder is generally thought to be based on biological factors – the structure and chemistry of the brain – and is responsive to medication such as mood stabilizers or antipsychotics, usually combined with psychotherapy to help people learn to manage their condition. Borderline personality disorder does not have a biological cause and medication is not the primary focus of treatment. The disorder is rooted in a combination of volatile temperament and developmental factors that affect emotional attachment such as abuse, or neglect. Several modes of psychotherapy are effective in treating it, usually over the long term, sometimes in combination with medication to treat a specific symptom such as anxiety.
At a particular point in time, symptoms of these disorders may be similar, making it critical to understand patterns of behavior over time. When not in a manic or depressive period, a person with bipolar disorder may function well. They may have close relationships that are affected by their episodes of illness but are otherwise stable.
The borderline personality seldom demonstrates stability. Their interpersonal relationships tend to to be chaotic and their emotional responses inappropriately intense.
Both disorders are serious conditions and while both can be successfully treated, their treatment options are very different and their success is dependent on a correct diagnosis and on a carefully crafted individualized plan for care and support.