Researchers Find Link Between Low Serotonin Levels and SIDS


During the first year after birth, a parent’s greatest fear is sudden infant death syndrome or SIDS which kills more than 2300 babies a year. Strides have been made to reduce the number of deaths with the “Back to Sleep” program that encourages parents to place babies to sleep on their backs rather than their fronts. However, the primary cause of SIDS has remained unclear.

When babies are placed on their stomachs (face-down), their exhaled carbon dioxide may accumulate in loose bedding, where it can be breathed back in. Normally babies have the ability to sense the high CO2 levels and automatically wake up and shift their head position to get fresh air. Babies who do not respond appropriately can suffocate and may not wake up.

Researchers from Harvard Medical School and the Children’s Hospital in Boston conducted autopsy studies on 35 infants who died of SIDS. In addition to being at an elevated risk for SIDS due to factors that included being born prematurely, being placed to sleep on their stomachs, and suffering a slight illness prior to death, the babies also had 26% lower levels of the brain chemical serotonin as compared to babies who died of other causes.


Serotonin binds to sites in the medulla oblongata region of the brainstem and regulates breathing, temperature, heart rate, sleeping, waking, and other automatic functions. The babies also had low levels of an enzyme that is involved in the synthesis of serotonin, called tryptophan hydroxylase or TPH2.

Co-author David Paterson hopes that the discovery will help to screen babies for serotonin levels and to find treatments to protect them from SIDS. Those developments are still likely years away, he says.

The Back to Sleep campaign and the National Institute of Child Health and Human Development encourages parents to continue to practice safe infant sleeping techniques, as all babies – even those with normal serotonin levels – are at a higher risk of SIDS during the first year of life. These include:

• Put baby to sleep on their back.
• Place baby on a firm surface such as a safety approved crib mattress
• Keep soft objects such as toys and loose bedding out of the crib
• Don’t smoke around the baby
• Don’t let the baby get overheated; dress him in light clothing and consider circulating air with a fan.
• Keep the baby close to you, but in a separate bed (no co-sleeping)
• Consider a pacifier