Not sure how relevant my experiences are to you, but I will offer them anyway.
When I paid for a Vit D deficiency test, started supplementing, and got my levels up to high/normal - my overall mood lifted
When I discovered that insomnia is a widespread symptom of magnesium deficiency, and started supplementing - my sleep improved significantly, which a knock on effect on my tension and overall mood
When I discovered that coffee (even decaff) was affecting my blood pressure, and dropped both tea and coffee - my stress, anxiety and sleep levels all improved.
I actually shudder to think what state I would be in by now, if I was still a coffee drinking, Vit D and magnesium deficient depressed insomniac with high blood pressure. It is not a pretty picture though.