From what I understand, low doses LSD or mushrooms sometimes (I think like 20% of the time) creates a long term (six months to permanent) change in mood for severely depressed people. I am also under the impression that there is no extra benefit from repeating doses more than once a year.

I think that walks in nature work significantly more often, but the effect is short term lasting days instead of months or years. Also, walking once or more a week is helpful long term.