George McCann has been diagnosed with a subtype of bipolar disorder called the "fear of harm" profile, and finds that a prescribed dose of ketamine every few days alleviates his symptoms. Michael Rubenstein for NPR hide caption

itoggle caption Michael Rubenstein for NPR

A rat neuron before (top) and after (bottom) ketamine treatment. The increased number of orange nodes are restored connections in the rat's brain. Ronald Duman/Yale University hide caption

itoggle caption Ronald Duman/Yale University