Assessment of cognitive impairment in HSV-1 positive schizophrenia and bipolar patients: Systematic review and meta-analysis.

A common characteristic among schizophrenia and bipolar disorder patients is cognitive dysfunction, especially for memory and attention. Recent evidence has suggested that cognitive impairment in schizophrenia and bipolar disorder patients could be associated with herpes simplex virus 1 (HSV-1) infection, due to the ability of HSV-1 to infect neurons in the temporal lobe, which plays a key role in the formation of memory and processing of sensory input. The objective of this review is to analyze the aggregate neuropsychological testing data from previous studies regarding the impact of HSV-1 infection on cognitive function in schizophrenia and bipolar disorder. A systematic literature search generated a total of 379 articles; 12 full-text case control and cross-sectional studies met the eligibility criteria to be included in the review. Pooled effects assessed the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) total scores and the three index scores for immediate memory, delayed memory, and attention in a random effects model. The overall effect for RBANS total score was in favor of the HSV-1 positive group (z = 3.10, p = 0.002). A statistically significant overall effect of cognitive impairment for memory and attention indices was in favor of HSV positive schizophrenia patients (z = 5.95 p < 0.00001). The findings from the meta-analysis suggest that serological evidence of HSV-1 infection has a significant impact on cognitive function with small to moderate effect sizes (-0.23 to -0.49), particularly affecting memory and attention, in schizophrenia and bipolar patients.