Any attempt to compare the definitions of symptoms listed for "primary
psychoses" with those adopted in studies of
psychoses in patients with
epilepsy (PWE) will encounter problems of heterogeneity within both conditions. In this manuscript, five psychotic illnesses listed in Diagnostic and Statistical Manual of Mental Disorders-5th Edition (DSM-5), that is, brief psychotic illness,
schizophreniform disorder,
schizophrenia,
delusional disorder, and
schizoaffective disorder are compared with postictal (or periictal) and interictal
psychotic disorders in PWE. After examining definitions of primary
psychoses, definitions of
psychoses adopted in the papers dealing with postictal and interictal
psychoses are summarized. Further, diagnostic criteria of five types of
psychotic disorders in PWE proposed in 2007 by Krishnamoorthy et al. are also discussed, which include postictal
psychosis, comorbid
schizophrenia, iatrogenic
psychosis caused by
antiepileptic drugs (AEDs) (AED-induced
psychotic disorder:
AIPD), and forced normalization. Evidently, a comparison between postictal
psychosis and
schizophrenia is pointless. Likewise,
schizophrenia may not be an appropriate counterpart of forced normalization and
AIPD, given their acute or subacute course.Based on these preliminary examinations, three questions are selected to compare primary
psychoses and
psychoses in PWE: Is postictal
psychosis different from a brief
psychotic disorder? Does
epilepsy facilitate or prevent the development of
psychosis or vice versa? Is interictal
psychosis of
epilepsy different from process
schizophrenia? In conclusion, antagonism between
psychosis and epileptic
seizures in a later stage of active
epilepsy seems not to be realized without reorganization of the nervous system promoted during an earlier stage. Both
genetic predisposition and the summated effects of epileptic activity must be taken into consideration as part of a trial to explain interictal
psychosis. Interictal
psychosis is an aggregate of miscellaneous disorders, that is, co-morbid
schizophrenia, AED-induced
psychotic disorders, forced normalization, and "epileptic" interictal
psychosis. Data are lacking to conclude whether differences exist between process
schizophrenia and "epileptic" interictal
psychosis in terms of negative symptoms, specific personal traits, and the "bizarre-ness" of delusory-hallucinatory contents. These discussions may shed light on the essence of process
schizophrenia, thus allowing it stand out and receive increased focus.