Effects of hyperbaric simulation of scuba diving pressure on plasma β-endorphin

In contrast to our previous studies on the submersion of scuba divers in a state of neutral buoyancy, neither plasma β-endorphin-like immunoreactivity (β-EIR) nor affective feelings were significantly changed in scuba divers by mimicking diving pressures of 2 feet (0.6 m) and 50 feet (15.2 m) for 20 min in a hyperbaric chamber. It is concluded that the submersion-induced increase in plasma β-EIR and accompanying changes in affect reported previously are not due solely to changes in pressure.