This block brings together schizophrenia, as the most important member of the group, schizotypal disorder, persistent delusional disorders, and a larger group of acute and transient psychotic disorders. Schizoaffective disorders have been retained here in spite of their controversial nature.

Includes a variety of disorders in which long-standing delusions constitute the only, or the most conspicuous, clinical characteristic and which cannot be classified as organic, schizophrenic or affective. Delusional disorders that have lasted for less than a few months should be classified, at least temporarily, under F23.-.