SIDS sufferers exhibit dysregulated autonomic function and altered neurochemistry, reduced brainstem 5-HT (5-hydroxytryptamine), tryptophan hydroxylase-2 (TPH-2), and 5-HT receptor binding and receptor expression, thereby providing proof that serotonin plays a pivotal role in SIDS [23,68-70]. This evidence concerns the gene TPH2 and sudden infant death syndrome.