I see where the two presentations of both the illnesses can be quite similar. I think this is why getting a patient's history is so important. I imagine the history the therapist has had with the patient will also be useful.

Also I think I noticed with BPD the person can react to external events. I remember telling who I thought was one that part of the reason I was hospitalized is the divorce I was going through, that this had at least something to do to trigger my mental state at the time, my episode of massive depression, the worst I have ever experienced in my life. He ruminated on this for awhile, came up to me, and put his hand through the window next to me. He smashed it to pieces. He needed to be restrained and taken back once again to lockup. Apparently this is a normal sequence of events for him. All he would do was mutter how I let a woman put me there in the hospital. This was far from the complete truth. But this is this only part that he managed to hear from me.

So what do you think? Would a person with this kind of violent reactivity be diagnosed as Bipolar?