Do the vegetables/lack of meat cause depression, or are already abnormal people attracted to yet another ostensibly “alternative lifestyle?”
Vegs I have known never get more than minimal sunshine thus lack vitamin D. Vitamin D is the only actually effective medication for depression and works without eliminating all moods and feelings like Xanax et al seem to do. In the winter supplementing with 5 or 10k of Vitamin D3 will be proof against Winter Blues as well as against flue and colds.
Excellent question....
The old chicken and egg question...