The old saying "Healthy body healthy mind" is never more true than when dealing with depression. It's an eye opener when you find out that years of eating a bad diet, which is usually one that you thought was good. Can leave residue toxins in the body that cause side effects such as depression. Not to mention a host of other ailments and diseases.
Unfortunately a lot of doctors don't pay much attention to this and find it easier and quicker to just prescribe drugs. Which in turn are another toxin that just bandaid the problem and in some cases compound it.
You wouldn't put crap oil and fuel in your bike, yet we do it to ourselves. I suffered depression years ago and got over it for good using alternative methods.
I hope you manage to shoot the black dog. If not there are other ways to skin him.