A mental disorder, also called a mental illness, psychological disorder or psychiatric disorder, is mental or behavioral pattern that causes either suffering or a poor ability to function in ordinary life. Many disorders are described. Conditions that are excluded include social norms. Signs and symptoms depend on the specific disorder.
The causes of mental disorders are often unclear. Theories may incorporate findings from a range of fields. Mental disorders are usually defined by a combination of how a person feels, acts, thinks or perceives. This may be associated with particular regions or functions of the brain, often in a social context. A mental disorder is one aspect of mental health. The scientific study of mental disorders is called psychopathology.