Wonder if it's sleep related problems at altitude that contribute.
I find it difficult to believe 2-3k ft starts presenting a problem due to altitude. Perhaps at 2-3 k ft places are different and don't haveas many people, friends, social network etc. i don't think any city and very few towns in VT, NH are above 2k ft. Yet opiod and heroin addiction are big issues in both states.
Keep in mind the actual % of people committing suicide is very small (not diminishing it) so even a small increase in the affects of altitude could show up statistically.