Maternal HSV-2 link to schizophrenia in offspring supported
MedWire News: Results from a Danish study support an association between maternal infection with the herpes simplex virus (HSV)-2) and an increased risk for schizophrenia in offspring.
Writing in the journal Schizophrenia Research, Preben Mortensen (University of Aarhus) and colleagues explain: "Among the several candidates of environmental risk factors for schizophrenia, intrauterine exposure to infectious agents has attracted considerable interest during recent years."
They add that a number of previous studies have focused on a possible association between schizophrenia and maternal HSV-2 infection, but they have produced conflicting results.
To investigate further, the researchers used the Danish Psychiatric Central Register and the Civil Registration System to identify 602 individuals born between 1981 and 1994 who had developed schizophrenia by 2005, as well as 602 mentally healthy controls matched for age and gender.
Blood samples collected from the participants within 7 days of birth were analysed for HSV-2 immunoglobulin (Ig)G antibody levels.
Any specific (Ig)G antibodies present in the samples can be assumed to be of maternal origin as children have not produced any significant levels by this age, say the researchers.
The researchers found that neonatal blood samples from 16.1% of schizophrenia patients and 11.1% of controls contained HSV-2 IgG antibody levels above 0.2 optical density units - the predefined cut point for seropositivity.
Analysis revealed that HSV-2 seropositivity was associated with a significantly increased risk for schizophrenia, at an incidence rate ratio (IRR) of 1.56, after accounting for maternal or sibling history of psychiatric illness, place of birth, parental age, gestational age, and immigrant status of the parents.
Adjustment for paternal psychiatric illness other than schizophrenia attenuated this risk slightly, to an IRR of 1.43.
Mortensen and team conclude: "The study replicates an association between maternal HSV-2 IgG levels and schizophrenia risk."
They add: "Since the confounding by familial risk factors is confined to paternal mental illnesses not belonging to the schizophrenia spectrum, we hypothesize that this confounding may be partly due to other risk factors, eg, other sexually transmitted infections, rather than reflecting variations in genetic liability to develop schizophrenia."
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By Mark Cowen