Psychological illness is responsible for considerable disability worldwide. The World Health Organization Global Burden of Disease Survey estimates that by the year 2020, major depression will be second only to ischemic heart disease in the amount of disability experienced by sufferers. Although different measures of disability have been used in different studies, they have consistently demonstrated that individuals with depression and anxiety disorders experience impaired physical and role functioning, more days in bed due to illness, more work days lost, increased impairment at work, and high use of health services. The disability caused by depression and anxiety is just as great as that caused by other common medical conditions, such as hypertension, diabetes, and arthritis. Comorbidity of depression with anxiety or medical illness further increases the disability experienced by sufferers. Recognition and treatment, however, relieve the burden imposed by untreated depression on the individual, society, and health services.