Mental illnesses may be caused by viral or microbial infections, scientists have found.

The strongest evidence links schizophrenia to prenatal influenza infection; pregnant women who become ill with the flu are more likely to give birth to children who will develop schizophrenia.

The body’s immune reaction, rather than the infections themselves, may be to blame for the resulting brain damage and psychiatric symptoms. Understanding the relation between infections and psychiatric disorders may someday allow us to prevent mental illness using drugs or vaccines.