The mystery of what causes Sudden Infant Death Syndrome has plagued the medical community for a long time. Now, medical researchers say, they think they have cracked the secret.
Doctors have found that babies who die of SIDS tend to have significantly lower amounts of serotonin than babies who die of other causes.
A lack of serotonin is suspected to hamper a sleeping baby's ability to wake up when its safety is threatened by a lack of oxygen or some other health hazard.
Researchers from the Children's National Medical Center in Washington, D.C., say the next step would be to find a way to identify babies who suffer from a lack of serotonin.