I truly believe that reducing inflammation is beneficial in mental illness and depression is right up there for that. There is emerging evidence supporting the role of diet in helping depressive illness.
How does the inflammation start – I put a lot of that down to the polyunsaturated oils and particularly in combination with fructose and refined carbohydrates.
I know of several people who have had a significant improvement of their depression on LCHF.
Part of that is just taking back control of part of your life and eating habits. Part is probably a reduction in inflammation. It can all help.