Why do people get depressed?

so...why do ppl get depressed? or even bigger question, why do depressed ppl say they dont know why they are depressed. "no reason why im depressed, i just am" well i dont believe in that. there has to be a reason why ppl are and get depressed. i dont understand how you can just be depressed out of nowhere. there has to be something thats making you unhappy in your life. whether its the people around you, the person you are in love with, your family, your friends, your job, your bills, where you live, what you do, and yourself ect ect. there must be a reason. ppl who claim they dont know, they do know. deep down inside, they know whats making them sad, but sometimes they just dont want to admit it to themselves..maybe they are ashamed, maybe they are embarassed...maybe they are in denial? who knows. all those bullshit ass commericals about it being a chemical imbalance in your brain and shit? guess what, thats all bullshit and there is no evidence of that being true! that is just a "theory", that it might be why ppl are depressed. so these big companies make you turn away from the real reason why you are depressed, they make you buy their meds in order to fix your depression instead of fixing what you really need to be fixing! your just taking that problem, puttin it in a hole, and just burying deeper and deeper. they just wanna make money off your ass, so they feed you lies...imbalanced chemicals my ass. i bet most ppl dont even know that its not true, but just "theory". but then again, ppl say that it worked for them...hmm placebo effect lookin ass....anyways, those are my thoughts about that subject, stop poppin pills!