In June 2010 I blogged about a study showing that Seventh-day Adventist (SDA) vegetarians had “less negative emotions” than SDA non-vegetarians (link).
Earlier this month, a cross-sectional study from Germany was released showing that vegetarians were more likely to have had mild mental disorders. The purpose of the study had been to see if vegetarians who eat less fish (for DHA) and get less vitamin B12 were more likely than non-vegetarians to develop mental disorders. It turned out that while the vegetarians did have higher rates of mental disorders, they had, on average, developed them before becoming vegetarian.
Many of the vegetarians did eat fish, but excluding them did not change the results. It is not clear how many, if any, of the vegetarians were vegan, but definitely not more than half (the percentage who never ate fish).
The data was taken from the German National Health Interview and Examination Survey (GHS) conducted in 1998/1999, making me feel less bad that it took me two weeks to get around to writing a post about it.
They did find that the vegetarians were more likely to develop an eating disorder after they became vegetarian, whereas the rest of the disorders (depression, anxiety, somatoform (hypochondria and pain)) tended to occur before becoming vegetarian.
I originally read this study for the B12 and DHA angle. As I read it and found out that more than half of the “vegetarians” were actually semi-vegetarians, I became less enthused about reporting on it, but in the end decided I should in case it was mentioned elsewhere on the Internet.
Hopefully, things have improved for German vegetarians in the last 10 years.
Michalak J, Zhang XC, Jacobi F. Vegetarian diet and mental disorders: results from a representative community survey. Int J Behav Nutr Phys Act. 2012 Jun 7;9(1):67. (link)