Geoffrey MillerVerified account

The much simpler explanation seems to be that psychological reasons for going vegetarian (e.g. deviancy, compassion for the world's problems, caring a lot about suffering, interest in dieting) are also things that cause mental health issues.

Yep. Without random assignment, there are way too many genetic and phenotypic confounds.

People who angst about eating and exploiting animals/animal products are more likely to angst about other stuff?

Perhaps we’re just depressed about all the suffering on factory farms

Yes and: Factory-farmed meat may be less healthy—including mental health—for humans to eat than is meat from smaller-scale agriculture and hunting.

And people who abstain from all meat eating may do so for reasons which co-occur to a significant degree with depression and related symptoms.

I tried giving up meat years ago. My body could not handle it. Most people I know are the same. I think vegans have a genetic difference which allows them to survive without eating meat. I prefer free range, of course. And hope to eat food that has not suffered. But must eat it.