Vegetarians have about twice as many depressive episodes as meat eaters, according to a new study.
The study, based on survey data in Brazil, agrees with previous research who found higher rates of the Depression among those who give up meat. However, the new study suggests that this link exists independently of nutritional intake.
It may seem straightforward to look at a link between diet and specific health conditions and assume that the former is causing the latter via some form of nutritional deficiency.
Yet the new analysis, published in the Affective Disorders Diaryconsidered a wide range of nutritional factors, including total calorie intake, protein intake, micronutrient intake and level of food processing.
This suggests that the higher rates of depression among vegetarians are not caused by the nutritional content of their diet.
So what could explain the link between vegetarianism and depression? Is there a non-nutritional mechanism that causes the first to cause the second? Or does the relationship depend entirely on something else?
First, it’s possible that depression makes people more likely to become vegetarians rather than the other way around. The symptoms of depression may include rumination of negative thoughts, as well as feelings of guilt.
Assuming that depressed and non-depressed people are equally likely to encounter the shocking truth of slaughterhouses and factory farming, it is possible that depressed people are more likely to ruminate on these thoughts and more likely to feel guilty about their role in creating demand. .
The depressed vegetarian, in this case, is not necessarily wrong to think so.
While depression is sometimes characterized by unrealistic negative perceptions, 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 perceptions of their own role and abilities.
In this case there is really cruel treatment of animals in meat production. And this is really due to consumer demand for cheap meat.
Second, adherence to a vegetarian diet may cause depression for reasons other than nutrition. Even though there is no “happy nutrient” missing from a vegetarian diet, giving up meat may cause depression in other ways.
For example, adopting a vegetarian diet can affect relationships with others and participation in social activities, and can sometimes be associated with teasing or other forms of social ostracism.
Notably, the new study is based on survey data collected in Brazil, a country famous for its meat-rich diet. Some survey data have shown a strong increase in vegetarianism in Brazil in recent yearsfrom 8% in 2012 to 16% in 2018.
However, the recent article polled more than 14,000 Brazilians and found only 82 vegetarians, or just over half a percent.
One has to wonder if the same link between vegetarianism and depression would be seen in India or other countries where vegetarianism is more of a social norm.
More importantly, as the the rate of vegetarianism is increasing in the UK and other developed countries, will we see the relationship disappear over time?
Finally, neither vegetarianism nor depression may cause the other, but both are associated with a third factor. It could be any number of characteristics or experiences associated with both vegetarianism and depression.
For instance, women are more likely than men to be vegetarians, and experience depression. However, the Brazilian study took gender into account, excluding this particular third variable.
One variable that has not been examined, but is likely related to both vegetarianism and depression, is exposure to violent images of the meat industry. Preventing animal cruelty is the most cited reason vegetarians give to avoid meat.
documentaries like Domination and earthlings that depict cruelty in the meat industry cannot easily be described as feel-good movies. One can easily imagine that someone who consumes this kind of media would become both a vegetarian and, especially when most people choose to look away, depressed.
There are several possible reasons for the link between vegetarianism and depression. This new study suggests that vegetarian nutrition is not the cause of depression.
Instead, vegetarian social experience may contribute to depression, depression may result in an increased likelihood of becoming a vegetarian, or vegetarianism and depression may be caused by a third variable, such as exposure to violent images of the meat industry.
Chris BryantHonorary Research Associate, Department of Psychology, University of Bath
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