People are gradually accepting that food can affect migraines, or that additives can affect ADHD kids, but many do not know that diet can affect mood. Diet responding adults with various symptoms also report feeling calmer, with more even mood. Parents report that their ADHD and ASD children are much less irritable, touchy or cranky. Like other symptoms it is not an all-or-nothing change but rather a decrease in the severity of the symptom. There have been reports of reduction in worry, anxiety or panic, even sadness and poor self-confidence. Most are not the prime reason for diet but the clear reactions some report remind us to monitor the milder ones that often occur and may be an important part of the improvement with diet investigation. For more detail see
https://foodintolerancepro.com/category/evidence-base/mood-the-role-of-diet/ and “The role of diet in mood” in the Articles on my site, and more in Tolerating Troublesome Foods.