It can make it alot worse. Scientific studies show that a certain fraction of the population is susceptible to psychosis and mental illness as the result of smoking pot over a period of time.

Personally, I also self-medicated with pot for anxiety and chronic pain before going manic. At the time I was on antidepressants and scaled up the marijuana when I became extremely nauseated for something like a month.
I don't know what would have happened if I hadn't been smoking pot. Maybe I wouldn't have gone manic.

I also felt really good being high and like my mind was on and clear and full of energy and then would crash and feel blunted when I came down.

BTW I'd love to do it again but its too dangerous for me and not worth it.