Ketamine

I don't understand why medical marijuana is illegal in my state but Ketamine is legal for depression treatment. Seems so backwards to me.

Anyways, next year I'm wanting to go back to therapy and the psychiatrist. I've tried a long list of meds in the past and none of them worked. Last time I was at my psych visit the doctor told me there are other treatment options for people who's depression doesn't respond to meds (treatment resistant depression). One option being transcranial magnetic stimulation and the other being Ketamine.

I've researched TMS and I don't think I want to go that route. Not that I'm fond of the idea of Ket either but has anyone tried it and had positive results?

How often do you have to go in for Ket treatment? Is it expensive? Covered by your insurance? Any negative side effects?