A bacterial infection during pregnancy is associated with an increased risk for development of a psychotic disorder in the child, according to a new analysis of data from a family study conducted in New England in the 1950s.

The role of infections in developing psychosis has been written about frequently in these Research Weekly blogs, in part due to the Treatment Advocacy Center founder Dr. E. Fuller Torrey's role in conducting this important research. Previous blogs highlighted the effects of infection by the parasite toxoplasma gondii in increasing risk for psychosis in individuals, as well as the effect of viral infections such as the Epstein-Barr virus.

However, bacterial infections have also been shown to have some association with an increased risk for developing a mental illness, due to the role of the immune system in fighting off these foreign invaders in the body. In addition, although there has been some research on the role of immune system activation in a pregnant mother and the subsequent risk of psychosis in their child, investigation on the role of maternal bacterial infection is limited.

Animal model studies allow research into complex biological processes over time that is not possible in humans. Previous animal model research has shown that bacterial infection in a pregnant mother can cause changes to both the structure and function of the offspring's fetal brain, which after birth shows behaviors and biological differences similar to humans with psychotic disorders. Therefore, real-world research into the role of maternal infections on the risk of developing psychosis in the child is needed, as well as examining if there is a gradient effect on the severity of infection during pregnancy.

The study authors utilized data from the New England Family Study that tracked more than 15,000 births from 1959 and 1966. Health records of the mothers were examined for history of infections during pregnancy, and follow-ups of the children, who are now in their 50s, were conducted.

Mothers who had a bacterial infection during pregnancy were 1.6 times more likely to have a child that later developed a psychotic disorder, according to the results. Mothers that had an infection during pregnancy that affected multiple organ systems had a more than three-fold greater odds of having a child who later developed a psychotic disorder. The authors write that these findings further support the role of infections and the immune system, especially infections during pregnancy, in the etiology of psychotic disorders.

These results have important implications as bacterial infections during pregnancy, such as urinary tract infections, are common due to physiological changes to the body during pregnancy and can often go undiagnosed because the symptoms are not obvious. Therefore, there is a vital role of public health in preventing infections during pregnancy and in promoting early diagnosis and treatment when they do occur. The study authors suggest more research is needed to understand the short- and long-term effects of infections during pregnancy as well as the effect of antibiotic medication use in pregnant mothers on both the mother and child.