Serotonin in the sudden infant death syndrome.

It seems likely that some infants who die from sudden infant death syndrome (SIDS) have a brainstem abnormality of the serotonergic system. Evidence suggests that infants who died from SIDS had defective respiratory and/or autonomic responses that led to death instead of recovery after an acute insult. The serotonergic neuromodulator system has roles in the control of cardiac autonomic and respiratory function, as well as now being identified as abnormal in infants with SIDS. This manuscript reviews the multiple roles of serotonin with reference to the functional aspects of the relevant brain regions. Correlations with pre- or postnatal exposure to stressors, or an underlying genetic process are also reviewed. Together, these studies indicate that perturbed function of the serotonin system will have significant physiological impact during early development. Understanding the functional importance of these systems assists understanding of the pathogenesis of SIDS. In conclusion, whether an infant inherits serotonergic defects and is therefore "inherently vulnerable", or whether postnatal stressors can induce the abnormalities, any functional abnormalities of the serotonergic system that result are likely to be subclinical in the majority of cases and not easily detected with current medical tools.