In its study, the U.S. Centers for Disease Control and Prevention looked at 2.4 billion drugs prescribed in visits to doctors and hospitals in 2005. Of those, 118 million were for antidepressants.
High blood pressure drugs were the next most-common with 113 million prescriptions.
The use of antidepressants and other psychotropic drugs -- those that affect brain chemistry -- has skyrocketed over the last decade.
http://www.cnn.com/2007/HEALTH/07/09/antidepressants/index.html