Before you dunk that next donut, you may want to consider the results of a new study. More junk food leads to an increased risk of depression, according to the authors. The study, published inPublic Health Nutrition, evaluated the eating habits of nearly 9000 Spanish adults, as well as their mental health. Overall, the risk for depression increased when they consumed more fast food and commercially-prepared pastries. At the beginning of the study, none of the participants had a diagnosis of depression, cardiovascular disease, diabetes, or high blood pressure. They completed questionnaires that evaluated fast food consumption (hamburgers, pizza, and sausage) and baked good consumption (donuts, muffins, and croissants). The authors divided the participants into five groups based on consumption patterns.
After more than 6 years of follow-up, the authors assessed whether the participants had been diagnosed with depression or prescribed antidepressants. The people with the highest consumption of junk food had a 37% increased risk of being diagnosed with depression compared with the lowest consumption group. The intermediate consumption groups also exhibited an increased risk of depression compared to the lowest consumption group.
The study was a prospective cohort study, so the results cannot conclusively determine cause and effect. In fact, both depression and eating habits may result from another common factor. But, the results were consistent, even after adjusting for variables such as age, gender, body mass index, smoking status, activity level, total caloric intake, and overall diet.
The participants in the highest consumption group were more likely to be single, less active, and have a poor quality diet compared to the other groups. And, the authors only evaluated the relative consumption of these foods, not the absolute consumption. More studies of larger, more heterogenous populations are needed to determine the absolute effects of diet on mental health.
In studies at the opposite end of the diet spectrum, healthy diets full of fresh fruits and vegetables, nuts, and fish and low in saturated fats appear to be protective against depression. Again, most of these studies are prospective cohort studies of fairly homogenous populations, but evidence is mounting that diet and mental health are linked. The size and scope of the association is unclear. But, for the time being, you may want to have a piece of fruit with your muffin or order a side salad with your pizza and try to offset your risk of depression.