Maternal Flu Linked to Schizophrenia

By John M Grohol PsyD
November 29, 2007

You may have missed this if you don’t regularly read The Washington Post, but staff writer Shankar Vedantam wrote an excellent article describing how recent research into schizophrenia is increasingly pointing to maternal infections during the first and second trimester of pregnancy — especially flu infections:

That’s because the newest studies suggest the culprit may not be infections such as the flu per se, but pregnant mothers’ immune reactions to such infections. Current guidelines recommend that pregnant women get a flu shot — and the point of the flu vaccine is to set off an immune reaction. If the risk for schizophrenia is increased as a result of maternal antibodies, might protecting mom and baby from the flu raise the risk the child could get schizophrenia years down the road?

[...]

Brown [a researcher] calculated that if the women had not had the flu during pregnancy, 14 percent of the schizophrenia cases could have been prevented, an effect he calls potentially enormous for a disease believed to have several complex genetic and environmental factors.

It’s an intriguing possibility and while the jury is still out whether this is truly the cause of (or one of many possible causes of) schizophrenia, it offers yet another piece of evidence of how maddeningly complex mental disorders really are. There is no “simple” here, no direct brain chemistry or single gene alone, or just a bad case of “poor mothering.”

And just to illustrate how much we shouldn’t read too much into twin studies to implicate genes, the article has a zinger:

Insel also cites evidence that genetics may play a more dominant role than the environment in determining who gets schizophrenia: Studies of identical twins show that when one child develops schizophrenia, the other has a 50 percent chance of developing the disorder, too.

However, some of the increased risk among identical twins may be a result of maternal infections during pregnancy — and not genetics, Patterson argues. That’s because those identical twins who share a common placenta — and who are, therefore, more likely to receive the same maternal cytokines — seem to have a higher risk of schizophrenia than identical twins who do not share a common placenta.

Twin studies in psychology and genetics have long been held up as a gold standard for implicating genes in a causative role of a mental disorder since, after all, the two people have the same genes. This theory offers an alternative explanation for such studies’ findings.

Of course more research is needed, as it is always is… This research update on schizophrenia indicates that the mystery of what causes schizophrenia is probably not going to be solved anytime soon.

Read the article: A Theory That Raises Questions

Dr. John Grohol is the CEO and founder of Psych Central. He has been writing about online behavior, mental health and psychology issues, and the intersection of technology and psychology since 1992.