Endorphins, ventilatory control and sudden infant death syndrome--a review and synthesis.

Evidence is reviewed which supports the hypothesis that sudden infant death syndrome and "near-miss" sudden infant death syndrome may be caused by overactivity of the endogenous opioid system (endorphins). The characteristic features of sudden infant death syndrome are listed, and then by reviewing effects that have been observed with (or which would be expected to result from) overactivity of the endogenous opioid system, it is shown that all of the characteristic features of sudden infant death syndrome may be opioid mediated effects. The hypothesis proposes that the endogenous opioid system is tonically overactive for weeks or months prior to death from SIDS causing the ventilatory abnormalities and subtle CNS dysfunction such as behavioral indifference, thermal instability and decreased responsiveness to pinprick which have been noted in these infants. Most significantly, excess CNS endorphin activity explains the quiet asphyxial death during sleep. Research strategies for proving the hypothesis are briefly discussed.