@OP...You are correct that people use mental health terms indiscriminately. From teens to older adults, I have heard many, many people claim to have bipolar diagnoses and other disorders. I can usually tell if they truly have that and have been diagnosed or they are just trying to claim it as their problem. For the life of me I don't know why anyone would want to have that label put on themselves for any reason other than immaturity or just plain old ignorance.
Worse than that to me are people that label others as "bipolar" because the person may be difficult, confrontational or emotional in their eyes. That is clearly ignorant when most of them have no idea what the hell they are talking about! I have a long lost cousin I recently spoke to and she stated that this person and another were bipolar, manic and or psychotic. She just did not like them and could not get along with them so they are "bipolar". Most of these issues are just plain old ignorance based. Just my opinion.