It's not though.

Very simply put depression causes inflammation in your body which in turn feeds back to the poor state of your neurotransmitters. Not to even talk about the lack of nutrients your body suffers from and what effects those have, because being depressed affects your appetite, which is determined by hormones.

If I would put you in a prison cell and feed you piss poor food without proper vitamins and whatnot, you would get depressed. Even if you had all the best coping mechanisms and enjoyed meditating 18 hours a day while exercising, it wouldn't take more than a month or two for the simple lack of nutrients to start fucking up your nervous system. You wouldn't be able to exercise or sleep properly and would definitely get depression.

So kindly stop it with that bs