Table 4.

One-Way Sensitivity Analyses on Key Assumptions

Assumption	Changed Case	Base Case	Total Costs (US$ 2008 in millions)	Δ%
Base case			11,025
12-mo prevalence	3.7%a	2.2%	16,385	+48.6
Treatment rate	41.4%b	27.1%	10,567	−4.1
% of suicides due to depression	60.0%c	27.6%	14,399	+30.6
Discount rate	3%	6%	11,912	+8.0
Definition of depression	Any mood disorder	Major depressive disorder	16,013	+45.2
Target age range	All ages	≥ 20 y	11,082	+0.5

^aThe 12-month prevalence of 3.7% is retrieved from the upper 95% confidence interval in the World Mental Health Japan Survey.⁷

^bThe treatment rate of 41.4% is retrieved from the upper 95% confidence interval in the World Mental Health Japan Survey.⁸

^cThe percentage of suicides due to depression of 60.0% is used in the previous cost-of-illness studies of depression.^20,21