Summary: A new study shows that vegetarians are twice as likely to suffer from depression as those who eat meat. While nutrition plays a role in depressive symptoms, researchers say that social factors and upset over the treatment of animals contribute to symptoms of depression.
Source: The conversation
Vegetarians have about twice as many depressive episodes as meat eaters, according to a new study.
The study, based on survey data from Brazil, echoes previous research that found higher rates of depression among those who give up meat. However, the new study suggests that this link exists independently of food intake.
It may seem simple to look at a link between a diet and specific health problems and assume that the former causes the latter through some form of nutritional deficiency.
However, the new analysis, published in the Journal of Affective Disorders, took into account a wide range of nutritional factors, including total calorie intake, protein intake, micronutrient intake, and the level of food processing. This suggests that the higher rates of depression among vegetarians are not caused by the nutrient content of their diet.
So what can explain the link between vegetarianism and depression? Is there some non-nutritional mechanism by which the former causes the latter? Or is the relationship based on something else?
First, it is possible that being depressed makes people become vegetarian more often than the other way around. The symptoms of depression can include having negative thoughts, such as feelings of guilt.
Assuming that depressed and non-depressed people are equally likely to encounter the devastating truth of slaughterhouses and factory farming, it is possible that depressed people are more likely to ruminate on those thoughts, and more likely to feel guilty for their part in creating the question
The depressed vegetarian, in this case, is not necessarily wrong to think this way. While depression is sometimes characterized as having unrealistically negative views, there is evidence to suggest that people with mild to moderate depression have more realistic judgments about the outcome of uncertain events and more realistic views of their own role and abilities.
In this case, there is really cruel treatment of animals in meat production. And this is really caused by consumer demand for cheap meat.
Second, it is possible that adherence to a vegetarian diet causes depression for reasons other than nutrition. Even if there is no “happy food” missing from a vegetarian diet, it may be that meat causes depression by other means.
For example, adopting a vegetarian diet can affect the relationship with others and involvement in social activities, and sometimes it can be associated with bullying or other forms of social ostracism.
Notably, the new study is based on survey data collected in Brazil, a country famous for its meat-heavy diet. Some survey data has pointed to a sharp increase in vegetarianism in Brazil in recent years, from 8% in 2012 to 16% in 2018. However, the recent paper surveyed more than 14,000 Brazilians and found just 82 vegetarians – barely more than half a percent .
One must wonder if the same connection between vegetarianism and depression would be observed in India or other countries where vegetarianism is more of a social norm. More importantly, if the rate of vegetarianism increases in the UK and other developed countries, will we see the relationship disappear over time?
Finally, it is possible that neither vegetarianism nor depression causes the other, but both are associated with some third factor. This could be any number of characteristics or experiences associated with both vegetarianism and depression.
For example, women are more likely than men to be vegetarian, and to experience depression. However, the Brazilian study took into account sex, which excludes this particular third variable.
One variable that has not been investigated but is plausibly linked to both vegetarianism and depression is exposure to violent images from the meat industry. Avoiding cruelty to animals is the most frequently cited reason vegetarians give for avoiding meat.
Documentaries such as Dominion and Earthlings that depict the cruelty in the meat industry cannot be easily described as feel-good films. One can easily imagine that a person who consumes this type of media would become both vegetarian and, especially if most people choose to look the other way, depressed.
There are several possible reasons for the link between vegetarianism and depression. This new study suggests that a vegetarian diet is not the cause of depression.
Instead, the vegetarian social experience may contribute to depression, depression may cause an increased likelihood of becoming a vegetarian, or both vegetarianism and depression may be caused by a third variable, such as exposure to violent images from the meat industry.
About this diet and depression research news
Writer: Chris Bryant
Source: The conversation
Contact: Chris Bryant – The Conversation
Image: The image is in the public domain
Original research: Closed access.
“Association between meatless diet and depressive episodes: A cross-sectional analysis of baseline data from the longitudinal study of adult health (ELSA-Brasil)” by Ingrid Kohl et al. Journal of Affective Disorders
Association between meatless diet and depressive episodes: A cross-sectional analysis of baseline data from the longitudinal study of adult health (ELSA-Brasil)
The association between vegetarianism and depression is still unclear. We aimed to investigate the association between a meatless diet and the presence of depressive episodes among adults.
A cross-sectional analysis was performed using baseline data from the ELSA-Brasil cohort, which included 14,216 Brazilians aged 35 to 74 years. A meatless diet was defined from a validated food frequency questionnaire. The Clinical Interview Schedule-Revised (CIS-R) instrument was used to assess depressive episodes. The association between meatless diet and presence of depressive episodes was expressed as a prevalence ratio (PR), determined by Poisson regression adjusted for potentially confounding and/or mediating variables: sociodemographic parameters, smoking, alcohol intake, physical activity, various clinical variables, even – assessed health status, body mass index, micronutrient intake, protein, food processing level, daily energy intake, and changes in diet during the previous 6 months.
We found a positive association between the prevalence of depressive episodes and a meatless diet. Meat non-consumers experienced approximately twice the frequency of depressive episodes of meat consumers, PRs ranging from 2.05 (95% CI 1.00–4.18) in the crude model to 2.37 (95% CI 1.24–4.51) in the fully adjusted model.
The cross-sectional design precluded the investigation of causal relationships.
Depressive episodes are more common in individuals who do not eat meat, regardless of socioeconomic and lifestyle factors. Nutritional deficiencies do not explain this association. The nature of the association remains unclear, and longitudinal data are needed to clarify the causal relationship.