Publication date: Mar 18, 2020
By 1919, the Spanish Flu pandemic had spread influenza to a third of the world’s population, or around 500 million people.
While today, we consider viral infections to be diseases of the body-they infect the lungs, give us fevers, stuffy noses, or a cough-throughout history there’s also been a strange link between influenza and psychotic disorders similar to schizophrenia, a severe mental disorder that can affect how people think.
More recently, this link re-emerged from the observation that babies born in the winter or early spring, when mothers may have been exposed to the flu, are more likely to develop schizophrenia as adults.
Some experts propose that influenza could interfere with fetal development through a mother’s immune system, or that influenza could bring on some kind of autoimmune disorder that interacts with the brain.
And, with a new viral infection sweeping the globe, one that’s not the flu but nonetheless shares some things in common with past pandemics, it’s especially relevant to lend a critical eye to how viruses and infections could influence our minds.
More than 200 papers have found that winter- and spring-month births are associated with greater risk for schizophrenia, raising the possibility that if mothers get the flu, it could somehow affect their children.
They found that children of women who had been exposed to the flu during the first half of pregnancy were three times more likely to have schizophrenia.
While not all the women who were exposed to the flu had children with schizophrenia-meaning it wasn’t a sure thing-they concluded that their data suggested up to 14 percent of schizophrenia cases would not have occurred if those mothers hadn’t been exposed to influenza during early to mid-pregnancy.
In Denmark, large studies have found that infections and autoimmune diseases throughout life are associated with the increased risk of many other mental disorders too.
A study from 2016 looked at every person born in Denmark from 1983 to 2002 and found that those with infections treated with anti-viral medications and those requiring hospitalizations were more likely to have schizophrenia and affective disorders.
There’s evidence that children who get a lot of infections when they’re young have increased rates of getting schizophrenia, and that postmortem brains of people with schizophrenia have abnormal immune cells.
Rhesus monkeys that were infected with the flu during pregnancy had babies with smaller brains and other abnormalities similar to those seen in schizophrenia, Spectrum reported.
(There is no evidence, though, of an association between the immune response brought on by the flu vaccine and schizophrenia or other psychotic disorders. )
Pollak said it could be that these viral infections and immune responses don’t cause schizophrenia on their own, but contribute to an overall risk.