eg just to paint the picture: you're depressed so you don't get out of bed, therefore you don't go do your workout, therefore you lack endorphins and look in the mirror and see squishy, you're sad about how squishy you are and so you get more depressed. You're more depressed so you also don't do your dishes, when you do get out of bed you are depressed you feel like a slob and you're squishy, so you get more depressed...
Whereas adding anti-depressants, and other virtuous cycle things like vitD/O3, exercise et al. Give the boost necessary to _make your life less depressing_ ...
So if you know someone who's depressed, it might be helpful to help them make their life less depressing too. (in addition to all the best medical advice!)
[1]- he's a real Dr... Dr. Alok Kanojia (Dr. K), a Harvard-trained psychiatrist (MD, MPH) specializing in modern mental health