I think it depends very much on both the strain and the character of the depression, too, Nailhead. From dysthymia to major depression to bipolar depression to some sort of adjustment/situational depression or grief, the illness itself can practically have as many varieties as there are strains of cannabis.

This is why we need research. Real, human, large-scale research. Followed by medical legalization and decriminalization. Because there is help to be had for plenty of types of depression if we look at how the different strains affect different types of depressive illness.