Retriever emailed an interesting article about pros, cons, hopes and doubts associated with the increasing use of ketamine (the party drug Special K) in the treatment of depression. You can find that article here.
Promising research findings have led to off-label prescription of ketamine for depression and clinics that provide extremely expensive infusion therapy for those who have not found help with other treatments. Lots of caveats, but I'm glad that another option may be opening up for those who find nothing else that helps.
Then there is this report of a small study that finds initial positive results with nitrous oxide for rapid relief from depression. Nitrous oxide is colloquially known as laughing gas.
Ketamine has been under study for some time. The small nitrous oxide study represents an entirely novel approach, so don't expect to find your psychiatrist supplying the gas in office any time soon. I've had it at the dentist a couple of times and love the stuff, though I didn't go in depressed, so I can't speak from experience about clinical benefits beyond the intended effects for dental patients.