An estimated 5 million Americans suffer from obsessive-compulsive disorder (OCD) and live diminished lives in which they are compelled to obsess about something or to repeat a similar task over and over. Traditionally, OCD has been treated with Prozac or similar drugs. The problem with medication, aside from its cost, is that 30 percent of people treated don’t respond to it, and when the pills stop, the symptoms invariably return.