SIDS is the third leading cause of death among infants aged between a week and a year, killing 2,500 infants yearly in the U.S. and thousands more globally. Its causes are believed to be many and are fiercely debated.

The Italian researchers have developed a mouse model of SIDS, also known as cot or crib death.

According to their findings, an imbalance of the neuronal signal serotonin in the brainstem is sufficient to cause sudden death in mice.

The brainstem is that part of the brain that ensures the link with the spinal cord and the Italian researchers have based their theory on the fact that victims of SIDS show alterations in those brainstem neurons that communicate using the signalling molecule serotonin

They overexpressed an important receptor that regulates serotonin signalling, called serotonin 1A autoreceptor.

"At first sight the mice were normal. But then they suffered sporadic and unpredictable drops in heart rate and body temperature. More than half of the mice eventually died of these crises during a restricted period of early life. It was at that point that we thought it might have something to do with SIDS," says Cornelius Gross, one of the researchers.

While a complete block of serotonin signalling does not lead to death, upsetting its intricate balance by overexpressing serotonin 1A autoreceptor can. In response to serotonin the receptor initiates a negative feedback mechanism that reduces serotonin release and dampens down the signal to the body.

The researchers caution, however, that it is unlikely that the exact same molecular mechanism leads to SIDS in humans.

Nevertheless, the mouse model will help to shed light on how serotonin signalling, when dysfunctional, can be life-threatening.

In May this year, a new research coming from British researchers has linked the bacterial infection with sudden infant death syndrome (SIDS).

For the study, pediatricians from Great Ormond Street Hospital for Children in London reviewed autopsies of 546 infants who had died of SIDS between 1996 and 2005. The researchers found dangerous bacteria in 181 babies, or nearly half of the 365 whose deaths could not be explained. Some 72 infant deaths had non-infective causes, such as congenital heart disease or an accident.

The researchers found high levels of Staphylococcus aureus and Escherichia coli bacterial in children who died of SIDS. Most of the bacteria were detected in the babies’ lungs and spleens.

Last year a report of Bristol University’s Institute of Child Life and Health revealed that in case of nine out of ten cot deaths babies had mothers who smoked during their pregnancy.

Before 1991, laying babies face down during their sleep had been mainly the cause for SIDS. Since then, due to the Back to Sleep campaign, which promoted parents should lay their babies on their backs to sleep, the SIDS has dropped almost three quarters. In addition avoiding exposing your child to cigarette smoke reduces this risk.