https://www.psychologytoday.com/blog/diagnosis-diet/201702/worlds-first-clinical-trial-finds-diet-works-depression Empirical study proves low sugar diet is excellent treatment for depression.  One suggestion is that "refined carbohydrates (sugar, flour, refined cereals, etc) non-foods put your blood sugar, insulin, hormones, and neurotransmitters on a dangerous invisible roller coaster. This destabilizes mood and increases risk for insulin resistance, which causes brain damage over time."

"clearly the most powerful way to fundamentally change your brain chemistry is through food, because that’s where the brain chemicals come from in the first place! I believe a healthy diet can in many cases reduce or eliminate the need for prescription medications."