Ketamine

Gerard Sanacora, a professor of psychiatry at Yale University, has treated hundreds of severely depressed patients with low doses of ketamine, an anesthetic and popular club drug that isn't approved for depression.

This sort of "off-label" prescribing is legal. But Sanacora says other doctors sometimes ask him, "How can you be offering this to patients based on the limited amount of information that's out there and not knowing the potential long-term risk?"

Sanacora has a simple answer.