The interface between epilepsy and psychiatry has a long and chequered history. Both epilepsy and psychiatry have been linked to gods, witches, and demons and the supernatural (1). Epilepsy was first referred by the Greeks as the “sacred disease.” In the earliest writings of Hippocrates, it was opined that epilepsy was a natural affection with a hereditary origin, with its pathogenesis in the brain (2). Therefore, the brain was the seat of both sickness and madness, and both were related to phlegm. There are several examples from this period that link epilepsy and psychosis. The story of Hercules, who is believed to have killed his own children in a fit of madness, has been alluded in the writings of both Hippocrates and Aristotle. The supposition that this was epileptic, relates to a Hippocratic treatise: “when the uterus is near the liver and the hypochondrium and produces suffocation, the woman turns up the white of her eyes, becomes cold, gnashes her teeth, saliva flows from her mouth, and she resembles the persons seized by a ‘Herculean disease’” (3). The perception of epilepsy and a variety of mental illnesses as being related to the moon was also prevalent among the Romans. This led to the condition being referred to as morbidus lunaticus and to the development of the word “lunatic.” In the Arab world, associations between epilepsy, mental illness, and demons remained. Descriptions linking religiosity, epilepsy, and mental illness emerged during this period, the visions of many soothsayers and prophets being alluded to as manifestations of epilepsy. Religious prophets Mohammed and Saint Paul were said to have periodically heard voices and fallen to the ground. The links between the demons, the moon, and epilepsy continued into the eighteenth century (4).

In the nineteenth and early twentieth centuries, epilepsy was a common diagnosis in the asylums and in some, patients with epilepsy were segregated in separate wards. Patients with epilepsy associated with insanity were excluded from older asylums (5). Patients who stayed in asylums were subjected to close scrutiny; hence, the more severely affected were looked after by psychiatrists and the less severely ill remained in the community and were treated by general physicians and neurologists (1). Freidrich Hoffman introduced the term
epileptic equivalents for mental disorders in epilepsy (6) and Heindrich Hoffman recognized that epilepsy and mental disorder often develop into one another (7). Bonhoeffer described multiple etiologies of organic psychosis (acute exogenous reaction) (8). Kraepelin, the outstanding pioneer of the modern psychiatric classification, identified most of the psychiatric disorders of epilepsy that can be presently recognized (Kraepelin E. Psychiatrie, 8th ed. Barth: Leipzig, 1923, Blumer, personal communication). He pointed out that all psychiatric changes manifesting in the preictal or postictal phases may also occur interictally, independent of convulsive events. Laszlo von Meduna postulated a biological antagonism between epilepsy and schizophrenia. Heinrich Landolt identified different types of transient psychotic episodes and their relationship with seizures and the electroencephalogram (EEG) (9,10). Dongier suggested that patients with centrencephalic epilepsy were as likely as those with psychomotor epilepsy to develop psychotic episodes (11).

Slater and Beard published their classic five-part paper on the schizophrenia-like psychosis of epilepsy (POE). In this paper, they proposed the presence of agonism between seizures and psychotic states (12). Flor-Henry opined that patients with psychosis have fewer psychomotor/psychosensory seizures and have epilepsy lateralized to the dominant hemisphere, and patients with schizophrenia-like psychosis, as compared with affective psychosis, have greater brain damage and preponderance of epilepsy lateralized to the nondominant hemisphere (13).

Although the interface between epilepsy and psychiatry has stimulated considerable interest and research over the years, much of this has been in the hospital and institutional populations. Few studies have been conducted in representative populations, and epidemiological data are scanty. Psychiatric disorders are common in epilepsy, and encompass the spectrum of conditions from those that are a direct consequence of epileptogenic activity, to others that are merely comorbid. There is considerable evidence from epidemiological research to suggest that the psychoses are greatly overrepresented in epilepsy. Both large hospital–based studies (14) and community-based surveys (15) have shown an increased prevalence of psychoses in people with epilepsy, the findings being true for both learning disabled and nonlearning disabled adult populations with epilepsy. Although population figures for the prevalence of psychoses are 4 per 1000 (16,17,18) the corresponding figure in epilepsy is between 7% and 10% (1), a clear overrepresentation. Kanemoto et al. examined the risk factors for psychosis within the temporal lobe epilepsy (TLE) group and concluded that a close relationship existed between TLE and interictal psychosis (19). Within this group, early onset of epilepsy and prolonged febrile convulsions were found to be associated with interictal psychosis. Schimtz et al. have pointed out that risk factors that are common to all types of epilepsies or psychoses are severity of epilepsy, which includes poor seizure control; multiple seizure types; and ictal loss of consciousness (absence and complex focal seizures), signifying cerebral dysfunction. It has been suggested that functional disturbance rather than structural lesions are associated with psychosis; hence, localized or lateralized cerebral lesions may not be necessarily present (20).

Although the epidemiological evidence favors the overrepresentation of psychoses in people with epilepsy, there is little by way of specific epidemiological data on the psychoses of epilepsy. Indeed, although hospital-based data indicates the presence of epilepsy-specific psychopathology, this has not been examined adequately in the epidemiological setting. Systematic population-based research using methods of ascertainment, and controls matched for age, sex, disability, and ethnicity, based on the International League Against Epilepsy (ILAE) classification of neuropsychiatric disorders
in epilepsy, incorporating instruments of psychiatric research as well as scales for seizure severity and disablement need to be conducted in the future.

The clinical content of POE is variable in its description, some cases being predominantly organic and others showing clear-cut affective-schizophreniform symptomatology. Clinically, psychoses may be divided as follows:

The first type has a clear relationship with cerebral dysrhythmias of epilepsy and may reflect ictal or postictal disturbances of cerebral function. Most cases in this category represent ictal automatisms, absence status, or postictal confusional states. The intermediate group shows both impaired consciousness and functional psychotic features. A combination of visual and auditory hallucinations, marked confusional states, paranoid delusions, and depression amounting to stupor can occur in these patients. TLEs appear to be associated with such manifestations. The third group constitutes psychotic illnesses, which manifest with clear consciousness and occur either as transient self-limiting episodes or as chronic or severely disabling forms. These may be affective, schizophrenic, or schizoaffective.

Chronic paranoid-hallucinatory states have also been described in patients with TLE (21,22). Delusions coupled with auditory hallucinations and ideas of influence occur. Unlike schizophrenia, the affect remains warm and hebephrenic deterioration is not seen. The psychosis may begin with decline of fit frequency. Slater et al. have illustrated that delusions that were mystical or religious commonly occurred, and passivity feelings of being controlled and ideas of persecution were prominent. Auditory hallucinations were predominant, although visual, somatic, olfactory, and gustatory hallucinations also occurred. Thought disorder, neologisms, and thought blocking were also seen. The commonest emotional disturbances were aggressiveness, irritability, and severe depression. Catatonic phenomenon of gross degree was rare and patients were friendlier and less suspicious in contrast to those with schizophrenia (12). Toone et al. have observed that catatonic syndromes were less common in patients with schizophrenia affected by epilepsy than in their nonepileptic counterparts. Delusions and hallucinations were more common. With acute onset, the prognosis was better. Recovery and improvement were seen in a third; however, perseveration, retardation, and impairment of memory were seen in many. The illness later progressed and resembled an organic cerebral disorder (23). Perez et al. found that these patients showed little intellectual deterioration and lived well within the community (24).