For a long time, tryptophan was a natural, well-performing standard medication for depression until it was banned worldwide for years because of a production error in a single Asian factory – at the very time when patent-protected synthetic antidepressants were introduced. The whole tryptophan thriller is described in detail in the book “Bye bye, booze!“
For the alcoholic, tryptophan is very important – and he may have a much higher demand for the amino acid than others, because in a biochemical emergency, the body empties the tryptophan stores to produce vitamin B3 (niacin), which is immensely important. The body needs this vitamin in large quantities to break down alcohol, but at the same time alcohol prevents it from being absorbed from food. Since the body from the Tryptophan the messenger material Serotonin is made, which is responsible for good tendency, the robbery at the Tryptophan leads to a Serotonin deficiency and not rarely as consequence to depressions.
This is described in detail in the book Alcohol adé.