Depression is a relatively common, but underdiagnosed condition in the general population. In 1988, the World Health Organization (WHO) launched a 14-nation study of psychological problems in general health care settings, and set the prevalence of current depression at10.4%; almost half these cases had not been recognized by primary care physicians (6, pp39–40). Depression is associated with comorbidities, especially anxiety, and the WHO study estimated that people with depression experience six or more disability days per month (6, Table 6).