References:
[1] Hilton MF, et al. “The Association Between Mental Disorders and Productivity in Treated and Untreated Employees,” Journal of Occupational and Environmental Medicine (Sept. 2009): Vol. 51, No. 9, pp. 996–1003.
[2] Kessler RC et al: Prevalence and Effects of Mood Disorders on Work Performance in a Nationally Representative Sample of U.S. Workers. American Journal of Psychiatry, Sept. 2006, pp. 1561-1568.