A campaign to encourage putting infants to sleep on their backs has lowered the number of SIDS cases, but new research may answer some bigger questions on what causes the syndrome. NBC's Nancy Snyderman reports.

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More reading on Seratonin and SIDS:

Low Production of Serotonin in the Brainstem a Likely Cause for SIDS
A summary of the study by Dr. Hannah Kinney of Children's Hospital Boston

Listen: Dr. Hannah Kinney, SIDS Researcher, Discusses Study
From 90.9, WBUR Boston

New Clue into Cause of SIDS
From NBC 5 in Southern Colorado