Key clinical point: In patients with schizophrenia, exposure to herpes simplex virus type 1 (HSV-1) is associated with reduced cognitive function.

Major finding: There was a significant deficit in functioning for seropositive individuals on the composite cognitive score (standardized mean difference [SMD], −0.28) and 8 cognitive domains: delayed memory (SMD, −0.30), processing speed (SMD, −0.26), reasoning (SMD, −0.17), verbal learning (SMD, −0.26), vigilance (SMD, −0.22), visual learning (SMD, −0.27), visual spatial (SMD, −0.36), and working memory (SMD, −0.11).

Study details: Meta-analysis of 9 studies (n=3,516) comparing cognitive function of HSV-1 seropositive vs. seronegative individuals with schizophrenia.

Disclosures: This study was funded by the Stanley Medical Research Institute. The authors declared no conflicts of interest.

Commentary

“Cognitive deficits are common among individuals with schizophrenia, with impairment spanning a broad range of cognitive tasks. The causes of cognitive deficit in schizophrenia are likely multifactorial, and might include both genetic contribution as well environmental exposure such as infection. Herpes Simplex Virus type 1 (HSV-1), also known as human herpesvirus 1, is a common infection that appears capable of causing cognitive impairments by both virologic and immunological mechanisms. Study findings suggest both a potential cause that could at least partially explain the cognitive impairment in people with schizophrenia as well as a potential avenue to investigate future therapeutic approaches.”

Martha Sajatovic, MD

Professor of Psychiatry and of Neurology

Willard Brown Chair in Neurological Outcomes Research

Director, Neurological and Behavioral Outcomes Center, University Hospitals Cleveland Medical Center

Case Western Reserve University School of Medicine