Mental illness:

The term that refers collectively to all diagnosable mental disorders. Mental disorders are health conditions characterized by alterations in thinking, mood, or behavior (or some combination thereof) that are all mediated by the brain and associated with distress or impaired functioning or both. Mental disorders spawn a host of human problems that may include personal distress, impaired functioning and disability, pain, or death. These disorders can occur in men and women of any age and in all racial and ethnic groups. They can be the result of family history, genetics, or other biological, environmental, social, or behavioral factors that occur alone or in combination.