Low Serotonin Levels May Be Key to Sudden Infant Death Syndrome

In the U.S., SIDS deaths have declined by more than 50% since 1990. Experts say that's partly due to practices believed to minimize the risk, such as putting infants to sleep on their backs rather than their stomach and avoiding soft bedding, which could lead to asphyxiation.

But SIDS is still the leading cause of death among infants age 1-12 months, accounting for about 2,750 U.S. deaths annually. It's defined as the death of an infant before his or her first birthday that can't be explained even after a complete autopsy, investigation of the death scene and circumstances, and a review of the medical history of the child and family.

Now, the new research suggests that a deficiency of serotonin in the brain stem (which controls vital functions during sleep, such as breathing, heart rate, and blood pressure) may help explain most of the deaths, says study researcher Hannah Kinney, MD, a professor of pathology at Harvard Medical School and a neuropathologist at Children's Hospital Boston.

"It is not going to explain all SIDS deaths," Kinney tells WebMD. However, she adds, "it will explain the majority." Her study is published in the Journal of the American Medical Association.