Mood disorders are psychiatric processes that can simultaneously affect a person’s emotions, energy, and motivation. Carbohydrates serve as fuel for brain activity. Carbohydrate metabolism and abnormal brain function can result in a variety of psychological and physiological disorders, the most common of which are depression and anxiety. The quantity and quality of dietary carbohydrates are crucial in mood disorders. Carbohydrate quality is generally determined by dietary fiber, whole grain and legume consumption, and glycemic index (GI) and glycemic load (GL) content of the diet. Dietary interventions for mood disorders often include the consumption of whole grains, high-fiber carbohydrate sources, and the avoidance of processed foods and added sugars. The gut-brain axis is a bidirectional communication system that significantly influences the relationship between diet and mood disorders. Increasing the consumption of prebiotic fibers, such as fructooligosaccharides (FOS), galactooligosaccharides (GOS), and inulin, shows promising results in improving depressive symptoms.