This study found that, after years of increased use of antidepressants, a trend reversal began in the early 2000s which included decreasing rates of adequate antidepressant treatment.  The downward trend preceded FDA black-box warnings institute in 2004.   

Harman, J. S., M. J. Edlund, et al. (2009). Trends in antidepressant utilization from 2001 to 2004. Psychiatric Services, 60(5): 611-6. DOI: 10.1176/appi.ps.60.5.611 http://psychservices.psychiatryonline.org/cgi/content/abstract/60/5/611 

Authors: Jeffrey S. Harman, Mark J. Edlund, John C. Fortne