Seems pretty useless to meditate much (aiming for real results) if one is very anxious or depressed. Sort of like running with mononucleosis. I've spent months in a rut, and now that I'm slowly just feeling better in general, my baseline keeps improving with minimal effort.
another point is that I find the shift in frame - eg: moving from concern with contents of experience, to an underlying dynamic - more helpful than the ability for meditation to ameliorate the symptoms of mood dysregulation, per se (although I suspect there can be an effect).