Forget all the bipolar crap. If after only 6 months I wasn't having fun with someone, or they were dragging me down with them, then it probably isn't meant to be. Particularly if it was noticeable after only 2 months.

If we were talking a year, 18months, and it had never been noticeable, and you thought they were the love of your life. Then yeah, I can see a reason for giving it a go, discussing it with them, asking them to seek help...trying (and not necessarily succeeding, but trying) to make it work.

But after 6 months, when you noticed after a mere 2. Consider it the same as finding out someone smoked after meeting them (which would be a huge issue to me personally), and take your get out of jail card. It's not your job to make them get help, and it's not your job to stick around so their life is better.

Unless...you're gonna tell me they are the love of your life, in which case you have a lot of thought ahead of you.

Me, i'd probably bail.