The study tracked the diets and medical conditions of 8,000 people over 22 years (all part of a larger study called the Whitehall Study II) using surveys about diet and doctors’ visits completed every few years. By keeping tabs on what the participants ate and the sorts of conditions they were seeing doctors to treat, the researchers could analyze correlations between diet and health outcomes. The one that popped out is that men who consumed 67 grams or more of sugar per day were 23% more likely to be diagnosed with depression in a five-year period than men who ate 40 grams or less.

Source: The Link Between Sugar And Depression: What You Should Know