Severe mental illness is often defined by its length of duration and the disability it produces. These illnesses include disorders that produce psychotic symptoms, such as schizophrenia and schizoaffective disorder, and severe forms of other disorders, such as major depression and bipolar disorder.
Illnesses that produce distortions of perception, delusions, hallucinations, and unusual behaviors are sometimes called thought disorders. Because the symptoms reflect a loss of contact with perceived reality, the disorders are also sometimes known as psychotic disorders.
Severe mental illnesses are treatable, and with proper treatment and management of the illness, people with these disorders can experience recovery.
A fact sheet in PDF format detailing symptoms, causes, and treatment for each of these disorders is available.