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A small but increasing number of people in Western
countries are choosing to restrict meat for various
reasons. While in countries such as India a high
proportion (35%) of the population follows a
vegetarian diet due to cultural and religious
traditions, rates in Western countries are much
lower.
Although our knowledge about the association between
vegetarian diet and physical health is based on
numerous studies, relatively little data is
available on the associations between vegetarian
diet and mental health.
A german study investigated associations between
vegetarian diet and mental disorders. Participants
were drawn from the representative sample of the
German Health Interview and Examination Survey and
its Mental Health Supplement (GHS-MHS).
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.
Diverse processes could in principle produce
differences between vegetarians and non-vegetarians
in rates of mental disorders.
On a biological level, nutrition status resulting
from vegetarian diet may affect neuronal function
and synaptic plasticity, which in turn influences
brain processes relevant for onset and maintenance
of mental disorders. For example, there is strong
evidence that long-chain n-3 fatty acids causally
affect risk for major depressive disorders.
Moreover, although evidence is less unequivocal,
vitamin B12 levels appear to be causally linked to
major depressive disorders.
Studies have reported that vegetarians show lower
tissue concentrations of long-chain n-3 fatty acids
and vitamin B12 which may elevate risk for major
depressive disorder.
Besides differences in nutrition status, vegetarians
and non-vegetarians differ in a number of
psychological and socio-demographic characteristics
that may influence their risk for mental disorders.
Vegetarians are predominantly female, are more
likely to live in urban areas and to be single. All
these socio-demographic factors are correlates of
the presence of mental disorders.
A number of studies have shown that vegetarians tend
to be slimmer, drink less alcohol, and exercise more
than non-vegetarians; they tend to define themselves
negatively by emphasizing what they do not do; they
tend to stress their dissimilarity from others and
thereby accentuate their differences from the
general society; some vegetarians base the choice of
their diet more on an ethical motivation.
On the whole, results strongly corroborate the past
findings in smaller samples of adolescents and young
adults, which have demonstrated that in contrast to
physical health, a vegetarian diet is not associated
with better mental health.
Whether compared with a control group of
non-vegetarians matched for important
socio-demographic characteristics, or with
non-vegetarians in general, vegetarians show
elevated prevalence rates of diverse mental
disorders.
Importantly, researchers found no evidence for a
causal role of vegetarian diet in the etiology of
mental disorders.
Rather, the results are more consistent with the
view that the experience of a mental disorder
increases the probability of choosing a vegetarian
diet, or that psychological factors influence both
the probability of choosing a vegetarian diet and
the probability of developing a mental disorder.
For more information
The International Journal of Behavioral Nutrition
and Physical Activity
Vegetarian diet and mental disorders: results from a
representative community survey
Johannes Michalak1, Xiao Chi Zhang and Frank Jacob.
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