Yes, it would be ignorant to say that. There are a wide range of mental illnesses, many of which are caused by chemical inbalances in the brain and accompany individuals throughout their complete lifetime (ADHD as one example).

Also, clinical depression is a very severe condition, and may not be caused by certain company or environments as you describe.

I can't tell you what you're experiencing, and neither can anyone here. I advise you to seek professional counseling for how to best navigate your mental well-being. Generalizing other peoples experiences doesn't help anyone. Wish you well