One of the most common features on this site are posts about the health benefits of a vegetarian diet. In general, vegetarians are healthier than meat-eaters, though people who eat a Mediterranean or Paleo diet and minimize meat are about as healthy as vegetarians.
Truth be told, vegetarianism isn’t always associated with positive health outcomes. In fact, when it comes to mental health, vegetarianism may be more strongly correlated with mental disorders than meat-eating. According to Vegetarian diet and mental disorders: results from a representative community survey:
Vegetarians displayed elevated prevalence rates for depressive disorders, anxiety disorders and somatoform disorders. Due to the matching procedure, the findings cannot be explained by socio-demographic characteristics of vegetarians (e.g. higher rates of females, predominant residency in urban areas, high proportion of singles). The analysis of the respective ages at adoption of a vegetarian diet and onset of a mental disorder showed that the adoption of the vegetarian diet tends to follow the onset of mental disorders.
In Western cultures vegetarian diet is associated with an elevated risk of mental disorders. However, there was no evidence for a causal role of vegetarian diet in the etiology of mental disorders.
None of this means that you are at a greater risk of developing a mental disorder if you are a vegetarian(the study showed that people became vegetarian after showing symptoms of a mental disorder). It shows just a correlation between mental disorders and vegetarianism. Further studies may find no such correlation.
But assuming this is true, why is it so? Vegetarians may just be more sensitive in general, and to animal suffering in particular. In this way, we are like artists. In some studies, creativity is also linked with mental disorders. If you remember my post, The Vegan Brain is Different After all!, it wasn’t that big of a surprise that the brains of vegetarians seem to be wired a little differently from the brains of meat-eaters. Although vegetarians may generally be more prone to mental disorders, vegetarians tend to have higher IQs, on average.
People who enjoy torturing or killing animals or other people are also very likely to have serious mental disorders, but of a completely different kind. It is depressing to even think about such people, and is obviously even more depressing for animal-loving vegetarians.