A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning.[4] Such features may be persistent, relapsing and remitting, or occur as a single episode. Many disorders have been described, with signs and symptoms that vary widely between specific disorders. Such disorders may be diagnosed by a mental health professional. 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 behaves, feels, perceives, or thinks. 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. Cultural and religious beliefs, as well as social norms, should be taken into account when making a diagnosis.Prevention programmes have been shown to reduce depression, both for children (e.g. through protection and psychological support following physical and sexual abuse) and adults (e.g. through psychosocial assistance after disasters and conflicts)