Vegetarians were found to be 74% more likely than non-vegetarians to score above 12 on the Edinburgh Postnatal Depression Scale (EPDS); indicating a high probability of severe depression.
Similarly, EPDS scores higher than 10 were 66% more prevalent in vegetarians, reported the research team from Bristol University. Scoring above the threshold of 10 indicates a likelihood of mild to moderate depression.
“Here we found that self–identification as a vegetarian was associated with an increased risk of depressive symptoms evaluated both as a continuous scale and using a cut-off of greater than 10 on the EPDS,” wrote first author Captain Joseph Hibbeln of the Section on Nutritional Neurosciences, National Institute of Alcohol Abuse and Alcoholism, USA.
“To our knowledge this is the first large epidemiological study to show a relationship between vegetarianism and significant depressive symptoms among adult men,” he added.
Causation not established
Self- reported data was used from 9668 male partners of pregnant women in The Avon Longitudinal Study of Parents and Children (ALSPAC). The participants self-identified if they were vegan or vegetarian. Results were adjusted for multiple confounding variables.
Researchers suggested that nutritional deficiencies (such as vitamin B12, iron or zinc) common in diets lacking meat might be a possible explanation for the results. However, they could not rule out the possibility of reverse causation; in other words that having depressive symptoms might change individuals’ dietary patterns making them more likely to be vegetarian.
Previous observational studies in males and females have reported similar links between vegetarianism and depression; again without being able to conclude a causal effect of vegetarian diets on mental health.
The researchers even speculate on the possibility that vegetarianism “is a marker for other psychiatric disorders manifesting with symptoms of both eating disorders and depressive symptoms.”
“This study does not resolve the question of whether adoption of a vegetarian diet will increase, or decrease the risk of depressive symptoms,” explained the researchers.
“But does suggest that a randomized controlled trial of selected nutrients or foods may be warranted.”
Source: Journal of Affective Disorders
Volume 225, pages 13-17. Published online ahead of print. DOI: 10.1016/j.jad.2017.07.051
“Vegetarian diets and depressive symptoms among men”
Authors: Joseph R. Hibbeln, Kate Northstone, Jonathan Evans, Jean Golding.