Ketamine is the source of some controversy: it works wonders for depression, and fast. But it's also addictive and potentially triggering for people in recovery. It's proven to effectively treat severe depression that won't respond to other medications. But because it affects so many receptor sites in the brain, and because it causes hallucinations and other psychedelic effects, there's a lot to consider. Former Chief Medical Officer Marvin Seppala, MD, joins host William C. Moyers to discuss.