According to a representative 2012 study by the International Journal of Behavioral Nutrition and Physical Activity, along with being slimmer, drinking less, and exercising more, vegetarians are also more susceptible than non-vegetarians to mental illness. The study listed some causal mechanisms:

- The biological effects of vegetarianism have an influence on the normal processes of the brain, which increases the chance for potential mental disorders.

- Individuals with mental disorders are aware of an empathetic for the suffering of animals, or may show more health-oriented behaviors, leading to selection of the diet.

- Development of a mental disorder that increases the likelihood of choosing a vegetarian diet, in which the onset of the disorder would precede the diet itself.

Other findings of the study are somewhat startling. Adolescents were more likely to be depressed and have contemplated or attempted suicide than non-vegetarians. Further, vegetarians more frequently reported having been told they have an eating disorder when they visited physicians; this coincides with another study that states adolescent vegetarians reported more deviant eating behaviors, such as high rates of dieting, purging, and laxative usage. Yet another study found higher rates of abnormal eating attitudes, low self-esteem, high social anxiety, and high trait anxiety. Turkish adolescents were also at increased risk for binge eating and other unhealthy weight control behaviors according to another.

This study was of a wider variety than most other mental health studies regarding veganism and vegetarianism. Other studies were also limited in that they were strictly self-report questionnaires, while no studies to date have used clinical diagnoses of mental disorders based on standard diagnostic interviews.

This latest study was a representative sample of adults between the ages of 18 and 65. There were 4,181 respondents. The diagnoses were assessed by a computer-assisted variation of the DSM-IV (the mental health manual used to diagnose illnesses). The primary pattern found and assessed was this: “Individuals suffering from a depressive, anxiety, or eating disorder as well as from a somatoform disorder and syndrome consumed less meat . . . Analysis in the subsample of non-vegetarians also consistently showed that people suffering from a mental disorder ate less meat than people without a mental disorder. For vegetables and fruits, fast food, and fish a less consistent pattern emerged, although there are view findings showing those without mental disorders to [sic] eat more of all of these kinds of food.”

There was a control group – but the control group showed even greater differences when matched with the full vegetarian sample. With the revelation that Newtown shooter Adam Lanza was a vegan, public perception of vegetarians and vegans being crazy or weird is likely to get a little worse before it gets better – even though many dietary studies suggest that vegetarianism is the best way to go to live longer and live healthier. What do you guys make of this?