The position of paranoid disorders within the classification of functional psychoses into manic-depressive illness and schizophrenia introduced by Kraepelin is still being disputed. (For this reason we are expanding these comments with some background material). In the 5th edition of his textbook (1896) Kraepelin places the state of dementia paranoides together with dementia praecox and catatonia among the dementing processes and lists the insanity that he came to call paranoia, along with periodical insanity, under the constitutional mental aberrations. In the 6th edition of his textbook (1899) Kraepelin subsequently describes a paranoid form of dementia praecox (divided into two course types) alongside the hebephrenic and catatonic forms and – independently thereof – the clinical picture of paranoia. This precisely expresses the ongoing dilemma concerning the affiliation of paranoid psychoses to schizophrenia: all, part, or none of them.

In like manner a further differentiation appears in the 8th edition (1909–1915), whereby Kraepelin describes the clinical picture of paraphrenia as an entity distinct from both the paranoid form of dementia praecox, subdivided into gravis and mitis types, and paranoia. Dementia paranoides gravis and mitis are characterized by a bizarre and poorly organized delusional symptomatology frequently accompanied by hallucinations, which, after a variable length of time, leads to a variably pronounced demential personality change (mild only in the milder type of course, in which the ‘core of the personality’ suffers little or no impairment).