Re: "RDS", there is definitely hard scientific evidence that different people have different "baseline arousal levels". Those for whom it's very low require more dramatic experiences to get a "charge". In extreme cases, they can be sociopaths. On the flip-side, these folks can be very calm under pressure. In more moderate cases, bomb squad members, anesthesiologists, special forces, etc. The converse is the "drama queen" (male or female) who may very genuinely feel on edge all the time.

Re: health insurance, when applying for individual coverage, you get asked a litany of questions about your participation in "high risk activities", some of which are rock climbing, scuba diving, etc. If you're honest, you might be denied coverage. Funny thing is that some of these activities have much lower injury incidence rates (injuries per hour of engagement in said activity) than stuff we all do all the time, like road biking. If it's group coverage, these questions are generally not asked. E.g. I help run a non-profit for Yosemite Search and Rescue, and one of the things we do is pay for health insurance coverage for the "SAR Siters" (rad climbers who live in the Valley and help with rescues on an as-needed basis).