The Link Between SIDS and Serotonin – The Atlantic

These earlier findings, coupled with the latest research, suggest that an abnormality in serotonin metabolism—leading to lower or higher levels in different parts of the body—could indicate an underlying vulnerability that increases a baby’s SIDS risk. Researchers are still working to understand a causal link, however.

Many questions remain. Because the researchers were specifically testing serotonin levels, they don’t know whether the 19 babies with elevated serotonin in their blood had any other abnormalities in common. It’s also unclear whether the same groups that suffer higher rates of SIDS deaths are also more likely to have elevated serotonin serum. For instance, black babies and Native American babies are more than twice as likely as white babies, Asian babies, or Hispanic babies to die of SIDS. Premature babies and boys are also disproportionately represented among SIDS deaths compared with full-term babies and girls. “The cost of testing and the rarity of the event are prohibitive to screening at the moment,” said Peter Blair, an epidemiologist who focuses on SIDS at the University of Bristol in England. “If we can improve identification of a small group at high risk, then maybe.”

One of the biggest questions posed by the latest study is: Just how big of a risk factor is increased serotonin in the blood? In other words, among babies who have higher levels of serotonin in their blood, how much more likely are they to be victims of SIDS? After all, most of the babies in the study group had normal blood serotonin levels.


Most researchers view the syndrome as part of a “triple-risk model,” meaning SIDS results from three interacting factors that affect the baby all at once. The three factors in the triple-risk model include the underlying vulnerability, the stressful environment, and the critical phase of development that the infant is in. Under this model, an infant with an underlying vulnerability would also have to be in a bad situation—like being placed on his or her stomach when put to sleep, which is unsafe for newborns—to trigger SIDS.

Although SIDS deaths are sudden, a latent vulnerability may be present for days or months prior to death, the researchers of the PNAS study wrote, and may even originate during gestation.

For the time being, the best advice for parents and other caregivers who are worried about SIDS is still to follow the “safe to sleep” guidelines: That means a baby should always be put to bed in an empty crib with a firm mattress. The crib should be free of any toys, bedding, blankets, or pillows. And the baby should be placed flat on his or her back.

But it will be hard to completely eliminate the risk for SIDS until scientists understand just where it comes from.

“Just as important with these findings,” says Blair, who did not work on the study, “is that we are getting closer to identifying causal mechanisms for SIDS. The welcome fall in [SIDS-death] rates is due to good risk-reduction advice rather than an increased understanding of why these infants die.”


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