I got started on Soylent and Joylent while depressed and it kept me (more than I would be) healthy while I went along. I eventually turned back to cooking when I was out of depression and craved varied, richer taste and more control over the sugar/carb/fat levels in particular meals.

I think Soylent was a great crutch during my downtime. I don't think it encouraged depression. In my case I argue it kept my body healthy while my mind wasn't, which is itself a bonus.