As a diabetic and a sufferer of Bi-polar, I can tell you that letting your blood sugar get out of control will f**k your head up.
Actually, I was being facetious. There is research done on the effects of a low carb/high fat diets and intermittent fasting on mental issues ranging from ADHD to schizophrenia to Parkinsons to Alzheimer’s that show positive results for all those conditions and more. They just don’t get much follow up or attention because no big money to make on diet of healthy, non-processed food. Big pharma and big food all want you to keep buying their chemicals, no matter the damage to your health.