I think that it's flaw to say vegetarian diet is bad for mental health because of poor definition.
One can live on soda, refine vegetarian product and plenty of fat and still get to be called vegetarian !!
I like the work of Neal Barnard MD. when it comes to diet and cognition.
A whole food plant based diet or starch based diet is the best to go if you want to attain health.#StarchSolution