These are severe psychiatric illness with serious distortion of thought, behavior, capacity to recognize reality and of perception (delusions ands hallucinations).There is inexplicable misperception and misevaluation; patient is unable to meet the ordinary demands of life.

Acute and chronic organic brain syndromes (cognitive disorders), such as delirium, and dementia. Prominent futures are confusion, disorientation, defective memory and disorganized behavior.

Functional disorders. No underlying cause can be defined; memory and orientation are mostly retained but emotion, thought and behavior are seriously altered. Schizophrenia (split mind) i.e. splitting of perception and interpretation from reality – hallucinations, inability to think coherently.

Paranoid state with marked persecutory or other kinds of fixed delusions (false beliefs) and loss of insight into the abnormality.