Going by the findings of a recent autopsy study by US researchers, the key reason behind the sudden infant death syndrome, or SIDS, possibly is a fairly low level of message-carrying brain chemical called 'serotonin' - which basically helps the brainstem in regulating automatic functions, including breathing, waking, and sleeping.

According to the researchers, abnormal levels of serotonin may impede the breathing of an infant, particularly in the so-called challenging situations, like breathing in excessive amounts of exhaled carbon dioxide while sleeping with their face down.

With the research corroborating earlier studies which suggest that making infants to sleep on their backs is the one of the most effective ways to diminish the SIDS risk, Dr. Hannah Kinney of Harvard and Children's Hospital said: "When the infant is breathing in the face-down position, he or she may not get enough oxygen. An infant with a normal brain stem would turn his or her head and wake up in response. But a baby with an intrinsic abnormality is unable to respond to the stressor."

Published in the Tuesday edition of the Journal of the American Medical Association, the study, which examined brain tissue from babies dying of SIDS, can potentially play a notable role in identifying babies who face the risk of SIDS, due to which at least 2,300 babies die within a year of their birth.