Yes, I think BP is a mental illness; however, I have come to think of it as a neurological illness. If I ever need to tell someone I am ill but it is not a close enough relationship, i tell them I suffer from a "neurological disorder." if you think about it, the medications used ( anti-psychotics, anti-seizure meds, depressiona meds, anxiety meds) all affect certain chemicals in the brain. I think in time, once there is less stigma, psychiatric diseases will be grouped along with neurological diseases. Just my opinion.