A number of epidemiological studies have established a link between insulin resistance and the prevalence of depression. The occurrence of depression was found to precede the onset of diabetes and was hypothesized to be associated with inherited inter-related insufficiency of the peripheral and central insulin receptors.
In a study of more than 1000 women, the team found that each standard deviation increase in the intake of zinc, magnesium, and folate was associated with a respective 48%, 40%, and 34% reduction in the risk for depression/dysthymia, after accounting for total energy intake.