Reporting in the Journal of the American Medical Association, they suggest that stress during sleep exacerbates defect in serotonin circuits.

Investigators at the Children’s Hospital in Boston have found that babies dying of sudden infant death syndrome (SIDS) have lower levels of serotonin in their brainstems than those dying from other known causes. They hope their findings could lead to tests to help identify babies most at risk of SIDS along with new therapeutic approaches to correcting the serotonin deficiency.

Their results are published in the Journal of the American Medical Association in a paper titled “Brainstem Serotonergic Deficiency in Sudden Infant Death Syndrome.”

Brainstem serotonin is involved in regulating autonomic body functions such as breathing, heart rate, and blood pressure during sleep, explains neuropathologist Hannah Kinney, M.D., and colleagues. Back in 2006, Dr. Kinney’s team demonstrated that SIDS is associated with abnormalities in the number of cells and receptors related to serotonin in the brainstem. It was, however, unclear whether SIDS was related to serotonin overproduction or underproduction.

Their latest study measured the levels of serotonin and tryptophan hydroxylase from the post-mortem brainstems of 36 infants who died from SIDS and two control groups including five infants who died from other acute causes and five hospitalized babies with chronic hypoxia-ischemia.

The results showed that in comparison with the control cases, brainstem serotonin levels were 26% lower in the SIDS babies, and tryptophan hydroxylase levels were 22% lower. The levels of binding to serotonin receptors were also more than 50% lower. 

“There’s something about sleep that unmasks the defect, which we believe is in serotonin circuits,” comments Dr. Kinney. “The baby experiences some kind of stress during sleep, such as re-breathing carbon dioxide in the face-down position or increased temperature from over-bundling, that cannot be conmpensated for by the defective brainstem circuits.”

The Children’s Hospital group also stresses that other factors such as sleeping face down can aggravate the baby’s risk of SIDS. Of the SIDS infants in the study, 95% died with at least one risk factor, and 88% died with at least two.

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