Chronic hallucinatory psychosis is a psychosis subtype, classified under "Other nonorganic psychosis" by the ICD-10 Chapter V: Mental and behavioural disorders.

The ICD includes a section classifying mental and behavioral disorders (Chapter V).

The NIMH Strategic Plan (2008) calls for NIMH to "Develop, for research purposes, new ways of classifying mental disorders based on dimensions of observable behavior and neurobiological measures."

Attempts to classify mental disorders and give them names ran into many difficulties.

In his 1818 textbook Störungen des Seelenlebens he classified mental disorders into different categories.

Under the supervision of institutional review boards, psychiatric clinical researchers look at topics such as neuroimaging, genetics, and psychopharmacology in order to enhance diagnostic validity and reliability, to discover new treatment methods, and to classify new mental disorders.

Eating disorders are classified as Axis I disorders in the Diagnostic and Statistical Manual of Mental Health Disorders (DSM-IV) published by the American Psychiatric Association.

He classified disorders affecting the macula, in the center of the eye, and discovered an important immune response involved in rejection of tissue grafts, which helped make corneal transplants more successful.

The American Psychiatric Association (APA) has classified somatoform disorders in the DSM-IV and the World Health Organization (WHO) have classified these in the ICD-10.

There have also been different approaches in trying to classify mental disorders.