[nyerp]

The survey population for this study was American Mensa members. I'm not surprised they found "those in the Mensa community had considerably higher rates of varying disorders" but I suspect this has more to do with who joins Mensa rather than high IQ.

As noted by Scott Adams, "It turns out that the people who join Mensa and attend meetings are, on average, not successful titans of industry. They are instead – and I say this with great affection – huge losers. I was making $735 per month and I was like frickin’ Goldfinger in this crowd. We had a guy who was some sort of poet who hoped to one day start “writing some of them down.” We had people who were literally too smart to hold a job. The rest of the group dressed too much like street people to ever get past security for a job interview. And everyone was always available for meetings on weekend nights."

[strlen]

Would be great to have a link to the actual study, but studies typically control for socio-economic-status, family situation, etc... I share the your general sentiment, but keep in that Mensa's threshold of 130 means that 2% of a population with a 100 median IQ (assuming a 15 SD test) is eligible to join.

While far from everyone eligible to join Mensa does so (and as you've said, there's a very good reason for that), there is likely large enough to be able to form a statistically significant sample that resembles the general population with the same IQ which I suspect is readily available (at least in US SES by IQ can be gauged from GSS -- where the WORDSUM question is a "good enough IQ test", or from college statistics -- where the SAT is also a "good enough" IQ test for the purpose of a general study; not sure about UK.)

This isn't a "correlation vs. causation": I don't believe the study was looking for or claiming a causal relationship; I suspect it could well be the reverse: increased anxiety about predators being a push for better ability to predict where the predator might appear -- i.e., visuo-spatial intelligence (there is also some data that suggest that Homo Sapiens intelligence may have evolved accidentally out of certain neurological disorders).

So if the question is "is this a real correlation", there's good reason to think that the experiment was indeed designed to handle any confounding factors like the one you suggested. This is probably a better experimental sample than "college students who volunteer to take part in a psychology study" and easily allows for the most obvious variables to be controlled.