Fast Food and Depression

There's been a fair amount of research into depression and diet, mostly focusing on the Mediterranean Diet in general, one component of it (olive oil) or looking at specific nutrients like omega-3 fatty acids and B vitamins. All of these are associated with a reduced risk of depression.

Researchers in Spain wondered if a poor diet might be associated with an increased risk of depression (Pub Hlth Nutr 2012;15(3):424-432). To find out, they made use of an ongoing study of university graduates in Spain that started in 1999. At the start of the study the participants responded to a detailed dietary questionnaire as well as providing information about their health, demographic information such as marital status and employment status, and their height and weight.

For their study, the researchers excluded all of the participants who reported being diagnosed with heart disease, high blood pressure, or poor cholesterol scores. They also excluded those who had been diagnosed with depression or who were taking antidepressants for any reason, resulting in a total of almost 9,000 people participating in the study.

Every other year until 2007 (when this study regarding depression was ended) the participants responded to regular update questionnaires which included questions about whether they had been diagnosed with depression. The diets of those who developed depression were then compared with the diets of those who did not.

They found that those who ate fast food (which the researchers defined as hamburgers, sausages or pizza - what, no Taco Bell in Spain?) the most frequently were 40% more likely to report developing depression than those who ate fast food the least. Those most-frequent fast food eaters actually ate a LOT more fast food: they ate an average of 22 times as much fast food, by weight, as those who ate the least.

What this means for you

The problem is that it's hard to say that X causes Y without a really good understanding of what exactly causes Y. While we can certainly see a link between those who eat more fast food being more likely to develop depression, that doesn't mean that eating fast food is actually causing the depression. Our understanding of the root causes of depression in terms of brain chemistry is still in its infancy. That said, if you or someone you love suffers from depression, encourage them to eat healthfully in addition to their other treatments. They'll feel physically better, and that may help them feel better emotionally.

First posted: April 18, 2012