Until defining characteristics were established almost 40 years ago in the DSM-III, Borderline Personality Disorder (BPD) was a vague and ambiguous concept. Because a primary characteristic is mood swings, some early researchers insisted BPD was merely a variation of Bipolar Affective Disorder (BAD). After all, if there could be Bipolar I and Bipolar II, why wasn't so-called Borderline Personality Disorder something along the line of Bipolar IV, V, or VI? ...

​Researchers discovered similarities and differences in metabolism in these two groups. Both groups, compared to controls, exhibited decreased metabolism in parts of the brain related to emotional control and social interactions. BAD II patients exhibited distinctly decreased metabolism in the cerebellum, brain stem, and parts of the cortex associated in other studies with neurobiological depression. BPD patients showed lower metabolism in other areas including the hypothalamus. The hypothalamus is intimately associated with the endocrine system, which involves stress responses and hormone secretions including cortisol, testosterone, and estrogen. The hypothalamus is also key in the production of oxytocin, which is related to maternal feelings and warm social behavior.

Long thought to be a hallmark feature of borderline personality disorder, the inability to gauge the emotions of others and then regulate their own is what can make the lives of those with this disorder exceptionally challenging. Perhaps someone you care about has this diagnosis or seems to show some of the classic symptoms of instability, problems in attachment, and lack of clear-cut boundaries. What happens when things go wrong? How does this person react? You may find yourself in a position of having to be the voice of reason as you try to get the individual to calm down. The loss of emotional control seems to occur most often in situations involving other people, which often means you’re the target. As you’re berated, cajoled, and criticized for a supposed emotional slight, you wonder if there’s any chance of helping this person gain some self-control.
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In contrast to those who lack emotional control, when distressed, people high in IER (Interpersonal Emotional Regulation) are indeed able to engage in such stress-busting strategies as seeking social support and sympathy from the important people in their lives. They can tell people how they’re feeling in a calm and non-accusatory manner. Another adaptive IER strategy is the use of problem-solving to deal with an emotionally upsetting situation. Getting practical advice is yet another known coping strategy that can both make people feel better and resolve difficult situations.

By contrast, people with borderline personality disorder, along with those who are anxious and depressed, engage in maladaptive IER strategies that don’t reduce their distress but only make it worse. Excessive reassurance seeking is one of those maladaptive coping strategies. Over the short-term, seeking reassurance may alleviate your distress, which only serves to reinforce your use of it. However, as an interpersonal strategy, it is draining on those people who must constantly help to put you out of your emotional misery. A second maladaptive IER strategy is venting, in which you try to make yourself feel better by letting it all out in the form of shouting and yelling. However, people don’t like to be around you when you do this, so as an IER approach, it won't help but will just make you more isolated and unhappy.