Mental health is as important as physical health to the overall well-being of individuals, societies and countries.
According to the World Mental Health Survey (2004) common mental disorders (such as depression, anxiety disorders, substance use disorders) are highly prevalent in Western and developing countries. Mental disorders tend to be chronic, strongly impair quality of life, cause excess mortality, and substantial societal costs. Major depression is the second disorder worldwide in terms of illnesses with the highest disease burden, directly after HIV/AIDS. Four of the ten most disabling disorders are mental disorders. Worldwide about 150 million people currently suffer from a major depressive disorder, almost a million commit suicide each year, and 90 million people are currently addicted to a substance. The proportion of disability due to mental disorders is predicted to continue to rise over the next several years.