A research report published in England this week suggests that a diet high in processed, fatty foods could cause depression, while a healthier diet could prevent it. According to news reports, the study, published in the British Journal of Psychiatry , found those who ate plenty of fresh vegetables, fruit and fish had a 26 percent lower risk of depression than those who ate mainly fried food, processed meat, high-fat dairy products and sweetened desserts. The researchers conducted their study by surveying about 3,500 civil servants about their dietary habits and their mental-health status. They conclude that antioxidants or a combination of nutrients in the healthier diet help protect against depression.

Read the research abstract and a popular-press article about the study.

Most of us can agree that a balanced diet including fresh fruits, vegetables, whole grains and limited amounts of fats and processed foods is a good idea. Nevertheless, I tend to question the conclusions of this study. The researchers surveyed the group regarding their eating habits, and correlated those with their risk of depression. In their conclusions, they suggest a cause-and-effect relationship: one diet causes depression while another prevents it. Now, I’m not a scientist, not do I play one on TV. I do, however, remember learning in my research methodology classes that this type of non-controlled survey research can identify relationships, but generally not cause and effect.

In this case, it seems to me, the relationship could be the other way around. Is it possible that depression leads people toward a less-healthy diet? I can imagine that a depressed person might become less conscious of health and nutrition than a non-depressed person, or possibly just seek some happiness in a plate of bacon and donuts. —John Maday, Drovers managing editor