Can Eating Too Much Sugar Lead to Depression?

For years, researchers have suspected that excess sugar in food and drinks can cause depression. One reason it was suspected was because people with diabetes have an increased incidence of depression that is beyond what would be expected only from the challenges of dealing with a chronic illness. Having diabetes is associated with two to three times the rate of depression compared to the general population.

The increased rate of depression in people with diabetes was thought to be due to rapid increases in blood sugar, followed by steep declines. These fluctuations can affect mood, causing irritability, anxiety, cognitive problems, and fatigue, and increasing the risk of depression.

Recent studies have demonstrated that excess sugar can cause depression in non-diabetics. For example, data from the National Health and Nutrition Examination Survey showed that a 100 mg per day increase in dietary sugar correlated with a 28 percent increase in depression (Zhang, 2024).

Another study showed that artificially sweetened beverages and not just excess sugar were associated with an increased incidence of depression (Xie, 2015). This research supports prior data about the role of artificial sweeteners in contributing to depression.

How does excess sugar intake increase the risk of depression? One major way is that excess sugar affects the function of the gut microbiome. A microbiome is a collection of trillions of bacteria, viruses, and fungi that live symbiotically both in and on the body. These microbes are found on the skin and in the GI tract ("the gut"), mouth, lungs, airways, and the genitourinary tract, including the vagina.

The gut microbiome is the largest one in the body. The food we eat provides nutrients for the bacteria; in turn, the bacteria complete the digestion of food, providing nutrients for us.

Excessive sugar intake can disrupt the gut microbiome by favoring strains of bacteria that thrive on sugar (e.g., Actinobacteria), which causes inflammation. There is also a decrease in the production of short-chain free fatty acids, which also produces inflammation (YuanYuan, 2025). Inflammation can cross the blood-brain barrier and increase the risk of depression.

Additionally, the change in the gut microbiome can disrupt the production of the neurotransmitters serotonin and dopamine, which also increases the risk of depression. The gut microbiome has a significant connection with the brain through the peripheral nervous system, the vagus nerve arising in the brain stem, and hormones produced in the gut. It is not surprising that the gut can influence the brain and vice versa—hence, the saying that he or she had a "gut feeling."

So, yes, excess sugar intake can cause depression. It can also cause anxiety and various other mood disorders. Anyone susceptible to depression or anxiety should be particularly conscious of their intake of sugar and artificial sweeteners.

Because having a dysfunctional gut microbiome is very common in depression, some physicians recommend taking probiotics and/or prebiotics to normalize the microbiome. If you are considering this, I recommend that you speak with your doctor or pharmacist first.

Peter M. Hartmann, MD, DLFAPA