Although depression is classified as a mental illness, researchers have discovered that the condition goes far beyond the human psyche. The feelings of sadness and despair that characterize depression may be symptoms of a disease that affects the whole body.

Findings published in the Journal of Clinical Psychiatry revealed a link between depression and oxidative stress, an imbalance brought about by the overproduction of unstable atoms called free radicals. (Free radicals cause damage to cells, which can lead to such health problems as diabetes, cardiovascular disease and dementia.)

According to researchers, people with depression were more likely to have higher levels of malondialdehyde, a compound that confirms the presence of oxidative stress. In addition, scientists noted that regular treatment among people with depression lowered levels of this toxic molecule and increased antioxidants to levels identical to those of folks who didn’t suffer from the disorder.

Consequently, researchers concluded that one way to treat depression is to reduce oxidative stress and improve antioxidant function in order to prevent free radicals from damaging cells—possibly by following a diet rich in antioxidants, such as those found in berries and citrus fruits.

That means healthy eating may also nourish the mind.