Not surprisingly, this has been a hot question among researchers and others, as both borderline personality disorder and bipolar disorder are characterized by extreme shifts in mood. In the case of borderline personality disorder, the shifts happen rapidly, and often in response to real or perceived insults, rejection/abandonment, and frustrations. This is somewhat different from the experience of switching in bipolar disorder, in which there is more of a kindling phenomenon in which symptoms build over a period of time, and may include substantial disturbances in sleep, changes in energy, changes in behavior and thought, and so forth.
The discussion around a connection between the two conditions is further fueled by the expanding theory of a bipolar spectrum. Looking at the variants of bipolar II and rapid and ultra-rapid cycling, it makes sense that people would look at the mercurial mood changes and unstable emotions of borderline personality disorder and wonder if the two conditions might exist along a single spectrum or have some other connection. What is emerging is that for individuals with both conditions it appears that both environmental and genetic factors are at play.
Many people with borderline personality disorder, which affects a greater number of women then men, have experienced significant trauma in their lives. The clinical picture of a person with both bipolar disorder and borderline personality disorder is of someone who is bouncing from crisis to crisis. Every element of his life, social, occupational, financial, is in chaos, and the person’s subjective experience of the world is like a sort of living hell.