Gravity is also a theory technically. :P

My apologies I'm just sassy today. I'm not trying to start anything. lol

That could be just a case of semantics too. It may not be chemical (I know just about nothing about anything medical so anything I say to that end would sound terribly ignorant) but it's still a chronic legitimate illness. I know for myself, sometimes my "coping method" has just been to run to the bathroom or take a long drive so people don't see me break. But the break still happens regardless.

For me there are other things going on too than just a mood disorder. Positive thinking won't get the voices in my head to stop yelling at me. I couldn't possibly think positively enough to make sure I sleep through the night. Being so hypo that I shake, that my blood pressure is higher... I wish I could control those things without medication. And for 15 years I tried... just about destroyed my life in the process... but damn I tried.

"Chemical imbalance" is just a nice, neat little way of saying "we have no idea"... but that doesn't make it any less real. Gravity or evolution are both scientific theories. It's all just semantics.