The figure 1 makes it look like an awful lot like there is no pattern at all for the vast majority of counties, and then the few with the very highest suicide rates are all very high altitude. They also mention this, but I'm not sure country is a great way to measure this. Death Valley and Mt Whitney, the lowest and highest altitude points in the contiguous states, are in the same county. Might also want to remove Vegas, which is high altitude and high suicide, but obviously for unrelated reasons.