Consumption of carbohydrates increases blood sugar levels to varying degrees, depending on the type of food ingested. The more highly refined the carbohydrate, the higher its score on the glycemic index (GI) scale. James E. Gangwisch, from Columbia University (New York, USA), and colleagues analyzed the dietary glycemic index, glycemic load, types of carbohydrates consumed, and depression for 69.954 postmenopausal women enrolled in the Women's Health Initiative Observational Study between 1994 and 1998. The team found that progressively higher dietary GI scores and consumption of added sugars and refined grains associated with increased risk of new-onset depression. In contrast, greater consumption of dietary fiber, whole grains, vegetables and non-juice fruits associated with decreased risk. The study authors write that: “The results from this study suggest that high-[glycemic index] diets could be a risk factor for depression in postmenopausal women. Randomized trials should be undertaken to examine the question of whether diets rich in low-[glycemic index] foods could serve as treatments and primary preventive measures for depression in postmenopausal women.”
James E. Gangwisch, Lauren Hale, Lorena Garcia, Dolores Malaspina, Mark G. Opler, Martha E. Payne, Rebecca C. Rossom, and Dorothy Lane. "High Glycemic Index Diet as a Risk Factor for Depression: Analyses from the Women's Health Initiative." Am J Clin Nutr., 2015 Aug;102(2):454-63.