Within the medulla, we have demonstrated that SIDS is associated with reduced 5-HT at source nuclei [29] and reduced 5-HT1A and 5-HT2A/C receptor binding in several target nuclei involved in cardiorespiratory control and/or arousal [18,28,30,32], findings that have been replicated in multiple independent cohorts over the last two decades [35–38,45]. Here, HTR5A is linked to sudden infant death syndrome.