Analogy between psychosis antedating epilepsy and epilepsy antedating psychosis

Patients with recurrent epileptic seizures after the development of psychosis (Psychosis-Epilepsy) have been regarded as belonging to a different clinical entity from those with epilepsy antedating the development of psychosis (Epilepsy-Psychosis). However, clinical characteristics of patients with Psychosis-Epilepsy have not been well described, except for early German studies. We aimed to estimate the reliability of distinction between Psychosis-Epilepsy and Epilepsy-Psychosis by comparing their clinical characteristics.

Among 312 patients with epilepsy and psychosis enrolled in this multicenter study, 23 patients had Psychosis-Epilepsy and 289 patients had Epilepsy-Psychosis (i.e., interictal psychosis). Demographic (i.e., sex, age at time of evaluation, and intellectual functioning), psychiatric (i.e., age at onset of psychosis, subtype of psychosis, duration of psychotic episode, and a family history of psychosis), and epileptic (i.e., age at onset of epilepsy, subtype of epilepsy, seizure type, and a family history of epilepsy) characteristics of both groups were compared.

Clinical characteristics, either in their psychoses or epilepsies, except for age-related variables, were equivalent between patients with Psychosis-Epilepsy and those with Epilepsy-Psychosis. Time intervals between onset of psychosis and that of epilepsy in the two groups showed a normal distribution curve.

The presence of many common features and the linear distribution of the time intervals did not fully support that Psychosis-Epilepsy and Epilepsy-Psychosis were two distinctly different entities. Among certain patients who have genetic vulnerabilities to both psychoses and seizures, psychosis may develop either antedating or postdating the development of epilepsy. These findings may suggest a necessary reconceptualization of psychoses in epilepsy.