Note: The study presented here was examining depressive symptoms, not major depressive disorder (MDD). In addition, this article is in no way meant to suggest that depression is “caused” by one’s diet, nor that certain diets can “cure” depression. Rather, it aims to show that the consumption of certain types of food may be one small aspect contributing to depressive symptoms.
Over the last few decades, depression and depressive symptoms have become increasingly more visible in society. As depression and depressive symptoms can substantially harm one’s life, more and more psychology studies have investigated the various factors affecting depression. One study examined the effects of consuming various types of foods on depressive symptoms in junior high school (grades 7-9) and senior high school (grades 10-12) in Japan (Tanaka & Hashimoto, 2019). This article will briefly present the findings of that study.
Methods
This study investigated 858 junior and senior high school students in Japan. The students were surveyed on the following topics. For the food questions, the answers were (never, 1-2 times a week, 3-4 times a week, 5-6 times a week, every day)
- “How often do you eat breakfast?”
- “How many days per week do you usually consume meat?”
- “How many days per week do you usually consume fish?”
- “How many days per week do you usually consume green and yellow vegetables?”
- “How many days per week do you usually consume milk and dairy products?”
- “How many days per week do you usually consume fruits?”
In addition, the Center for Epidemiologic Studies Depression scale (CES-D) was used to measure depressive symptoms. Respondents were asked to indicate how often they experienced 20 different depressive symptoms. On this measure, higher scores suggest more severe depression.
Finally, the participants were asked about their age, sex, and sleep duration. Sleep duration was measured with the following question: “How many hours of actual sleep do you get at night (average hours for one night)?” The responses were categorized into five groups: <four hours/night, four or more but less than five hours/night, six or more but less than seven hours, seven or more but less than eight hours, and eight or more hours.
Results
The following results were obtained:
- Boys and girls in junior high school reported significantly higher breakfast consumption than boys and girls in senior high school.
- Girls in senior high school reported significantly lower milk and dairy consumption than the other three groups, but there were no other differences among the four groups in terms of consumption of other foods.
- Senior high school students had significantly higher CES-D score than junior high school students, indicating higher levels of depression.
- Girls had higher CES-D scores than boys.
- Sleep duration was significantly negatively correlated with CES-D score.
- Breakfast consumption was significantly negatively correlated with depressive symptoms in junior and senior high school students.
- Green and yellow vegetable consumption was significantly negatively correlated with depressive symptoms in junior and senior high school students.
- Fish consumption was found to be significantly negatively correlated with depressive symptoms in junior high school students only.
Wrapping up
CES-D score was found to increase with age. In addition, for both junior and senior high school students, increased breakfast consumption and increased consumption of green and yellow vegetables were found to be correlated with reduced depressive symptoms. Prior research has shown that breakfast is negatively correlated with depressive symptoms, but the finding regarding green and yellow vegetables is novel.
Again, this does not mean that depression is “caused” by not eating breakfast or not eating green and yellow vegetables. In addition, it does not mean that depression can be “cured” by eating breakfast as well as green and yellow vegetables. However, it does suggest that eating breakfast and eating green and yellow vegetables may help reduce depressive symptoms for some people.
References
Tanaka, M., Hashimoto, K. (2019). Impact of consuming green and yellow vegetables on the depressive symptoms of junior and senior high school students in Japan. PLoS One, 14(2), e0211323. doi: 10.1371/journal.pone.0211323.
