Childhood viral CNS infections increase psychosis risk

By Mark Cowen

Viral infections of the central nervous system (CNS) in childhood are associated with nearly a two-fold increased risk for non-affective psychosis and schizophrenia in adulthood, a review and meta-analysis of published studies shows.

"These findings suggest that the vulnerable period during which harmful events with respect to brain development may increase risk of psychotic illness is not confined to prenatal period," say the study authors.

Golam Khandaker (University of Cambridge, UK) and colleagues searched the literature for published studies that included data on childhood infections from birth until the age of 18 years and adult diagnoses of non-affective psychosis and schizophrenia at the individual level.

Studies that used population-level data were excluded from the analysis, as were those based on neonatal blood samples that measured specific antibodies, as these represent fetal exposure to maternal infection rather than newly acquired infection after birth.

In total, seven studies met criteria for inclusion in the analysis.

A meta-analysis of data from 2424 cases and more than 1.2 million controls revealed that viral infections of the CNS in childhood is associated with a 1.7-fold increased risk for non-affective psychosis in adulthood. There was no evidence of significant heterogeneity between studies.

Furthermore, in a separate meta-analysis involving 1035 cases and more than 1.2 million controls, the researchers found that viral infections of the CNS in childhood were associated with 1.8-fold increased risk for schizophrenia in adulthood. However, there was evidence of some heterogeneity between these studies.

The team found no evidence for an association between bacterial infections of the CNS in childhood and an increased risk for psychosis in adulthood.

Khandaker et al conclude: "These findings indicate childhood CNS viral infections increase the risk of adult psychotic illness."

They add: "Possible mechanisms may include both direct effects of pathogens, and the effects of inflammatory response on the developing brain."

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