http://www.sfgate.com/life/article/Vegetarians-depression-meat-eaters-11818334.php
“The Bristol University study, published in the Journal of Affective Disorders, explained that vegetarians are more susceptible to Vitamin B12 and mineral deficiencies, which has negative effects on mental health.”
And so it was spoken.
And so it was good.
Amen
I take it you didn’t pay attention in your "scientific method " classes. 
http://www.jad-journal.com/article/S0165-0327(16)32391-6/abstract
Vegetarian diets and depressive symptoms among men
Method
Self-report data from 9668 adult male partners of pregnant women in the Avon Longitudinal Study of Parents and Children (ALSPAC) included identification as vegetarian or vegan, dietary frequency data and the Edinburgh Post Natal Depression Scale (EPDS). Continuous and binary outcomes were assessed using multiple linear and logistic regression taking account of potential confounding variables including: age, marital status, employment status, housing tenure, number of children in the household, religion, family history of depression previous childhood psychiatric contact, cigarette and alcohol consumption.
I bet there’s something there. Personally, I’ve found that meat, more than any other food, has a mood stabilizing effect on me, whatever that reason may be.