WORTH LOOKING INTO: “Correlational health studies would be more impressive (and useful) if they included IQ and personality data.”
As for this particular finding, the apparent link between depression and processed food consumption, assuming it’s real at all, what’s behind it? Well, what does processed food consumption correlate with (hint: negatively)? IQ. This is indeed the subject of James Thomspons’ latest post (IQ, Neuroticism, booze, and those damn vegetables again).
On that, one very large study (of Swedish conscripts) found that IQ was negatively correlated with severe depression (and other things like schizophrenia). So there’s that, anyway.