Kratom as an Anti-depressant

Has anyone used it as an 'on demand' antidepressant, or investigated it for this purpose?
I find that it seems to increase motivation for me, but I'm thinking it's doing this primarily through an antidepressant mechanism rather than as a stimulant. If I'm in a rut, I tend to waste a lot of time and get nothing done, but Kratom gives a massive lift that's enabling me to get on with a lot of tasks that I'd otherwise put off. Also I tend to do activities that I enjoy more, whereas normally I wouldn't even bother. Stimulants that I've tried in the past do not have the same effect...