Strenuous activity at altitudes above 8,000 m often leads to fatal brain swelling, even among those who are physically fit and have spent time acclimating. The

Strenuous activity at altitudes above 8,000 m often leads to fatal brain swelling, even among those who are physically fit and have spent time acclimating. There have been several studies indicating that mountain climbing leads to brain damage, even among world-class climbers. Similarly, there is evidence that scuba diving to depths below 40 m or so damages the brain. We didn't evolve at extreme altitudes or depths. It's probably best to stay away from them if you value your mental fitness or life.