Effects of diving experience on submersion-induced increases in plasma levels of β-endorphin in scuba divers

The submersion of eight male scuba divers in a state of neutral buoyancy for 20 min resulted in a significant increase (mean, 20%) in plasma β-endorphin immunoreactivity (β-EIR), and all subjects reported post-submersion feelings of well-being, relaxation or euphoria. The increase in β-EIR was negatively correlated with age (r = −0.727) and diving experience (r = −0.860), and positively correlated with the amount of air usage during submersion (r = 0.863). Thus, diving experience appears to influence many of the nonsubjective parameters measured.