If you're looking for potential solutions for depression and other mental illnesses, check out the book Change Your Diet, Change Your Mind by Georgia Ede. She details the evidence that's piling up in favor of a low carbohydrate/keto/carnivore diet curing multiple mental issues, including depression.

Also Brain Energy: A Revolutionary Breakthrough in Understanding Mental Health by Chris Palmer goes over the same issues and recommends the same solution (but it's not as user-friendly)

Or just listen to some interviews with these two authors. They're amazing.