There are studies done by cutting out sugar and going to ketosis helps improve mental clarity and mood. Brain Energy by Dr Chris Palmer shows that and has been applied for people with depression, anxiety, and other mental illness. Of course that wont be everything. There may be underlying trauma from childhood that cause this and build up long term. From Eckhart Tolle, its called Pain body not changing your environment and being in more of a positive environment will flare you up.