Nancy A. Melville

October 16, 2017

SAN DIEGO — A previous admission for epilepsy is associated with a significantly increased risk for a subsequent readmission for schizophrenia compared with previous admission for other medical reasons, new research suggests.

"Epilepsy patients admitted who have known psychiatric disease, especially psychosis, may warrant targeted psychiatric screening during their admissions given their clearly higher risk for readmission for psychosis," said first author, Kyle C. Rossi, MD, from the Department of Neurology, Icahn School of Medicine at Mount Sinai in New York City.

The findings were presented here at the ANA 2017: 142nd Annual Meeting of the American Neurological Association.

Epilepsy is known to have a bidirectional link to various psychiatric comorbidities; patients with epilepsy are more likely to have schizophrenia and those with schizophrenia are more likely to have epilepsy, Dr Rossi explained.

To look specifically at the intermediate-term risk for schizophrenia/psychosis severe enough to warrant hospital admission, Dr Rossi and colleagues evaluated data from the Nationwide Readmissions Database, where they identified 58,278 first-time admissions for epilepsy as a primary reason for admission.

Those patients were compared with 215,821 index admissions for stroke and 973,078 admissions for other common medical causes, including pneumonia, urinary tract infection, congestive heart failure, and chronic obstructive pulmonary disease.

At 90 days after the index admission, there were 683 per 100,000 readmissions for schizophrenia or psychosis in the epilepsy group compared with 92 per 100,000 in the stroke group and 58 to 206 per 100,000 in the medical group.

After adjustment for factors including age, sex, income, drug abuse, alcoholism, psychiatric history, and index hospitalization characteristics, patients with epilepsy had more than a four times greater risk of being readmitted for schizophrenia (hazard ratio [HR], 4.31) compared with the stroke group, and about twice that of the medical group (HR, 2.32).

Factors associated with a greater risk for readmission for schizophrenia or psychosis included a psychiatric history or discharge to a location other than home.

Meanwhile, factors that were associated with a reduced risk for readmission included age greater than the mean, female sex, higher income, and higher severity of All Patients Refined Diagnosis-Related Groups at index admission.

While some types of psychosis are clearly associated with epilepsy, such as psychosis occurring during and immediately after seizures, or resulting from antiepileptic medications, the link between epilepsy and schizophrenia is less understood, Dr Rossi said.

"Very little is known about the specific pathophysiology underlying psychosis," he said. "It can result from a variety of genetic, toxic, and metabolic causes. Likewise, schizophrenia is likely more of a spectrum disorder actually composed of multiple 'schizophrenias' of different etiology, but with a common phenotype involving psychosis."

And while no evidence indicates that treatment of epilepsy reduces the risk for schizophrenia, the severity of psychiatric illness appears linked to the severity of epilepsy, Dr Rossi said.

"It has been shown in large administrative studies that severity of depression, for example, is closely associated with the severity of epilepsy in patients with both."

The study adds to the mounting research on epilepsy and mental illness, commented Jack M. Parent, MD, professor of neurology, director of the Neurodevelopment and Regeneration Laboratory, and codirector of the Comprehensive Epilepsy Center in the University of Michigan Medical School, Ann Arbor.

"This abstract is important because the epilepsy research community is increasingly recognizing the link between epilepsy and psychiatric comorbidities," he told Medscape Medical News.

Patients with epilepsy are known to have a very high incidence of coexisting depression, but recent research indicates that patients with depression also have a higher likelihood of developing epilepsy or being refractory to antiseizure treatment, Dr Parent said.

"This effect suggests that the pathophysiology underlying these disorders involves shared neural circuitry."

"The present abstract expands this idea to schizophrenia, providing evidence that patients with epilepsy are more likely to be admitted with schizophrenia or psychosis," he said.

"I believe that this is important work that may eventually provide clues to the pathophysiology of schizophrenia and psychosis."

A limitation of the study is the possibility that some patients admitted with "epilepsy" may have been misdiagnosed and instead have had psychogenic nonepileptic seizures, as one would expect this disorder to be more common in a psychiatric population, Dr Parent noted.

"Overall, however, the work provides new impetus to explore the possible bidirectional nature of the comorbidity between epilepsy and schizophrenia/psychosis."

The authors and Dr Parent have disclosed no relevant financial relationships.

ANA 2017: 142nd Annual Meeting of the American Neurological Association. Abstract S196. Presented October 16, 2017.

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