This topic intrigued me and I did a little research on Tryptophan. It looks like it also converts to Niacin as well as Melatonan and Serotonin.
Niacin has been used in the treatment of alcoholism as well. It's essentially is Vitamin B3.
Apparently the founder of AA BillWilson was very interested in nutrient solutions to alcoholism before his death and experimented with Niacin.
Here's an excerpt: "Bill was very curious about it and began to take niacin, 3 g daily. Within a few weeks fatigue and depression which had plagued him for years were gone. He gave it to 30 of his close friends in AA and persuaded them to try it. Within 6 months he was convinced that it would be very helpful to alcoholics. Of the thirty, 10 were free of anxiety, tension and depression in one month. Another 10 were well in two months. He decided that the chemical or medical terms for this vitamin were not appropriate. He wanted to persuade members of AA, especially the doctors in AA, that this would be a useful addition to treatment and he needed a term that could be more readily popularized. He asked me the names that had been used. I told him it was originally known as vitamin B-3. This was the term Bill wanted. In his first report to physicians in AA he called it "The Vitamin B-3 Therapy." Thousands of copies of this extraordinary pamphlet were distributed. Eventually the name came back and today even the most conservative medical journals are using the term vitamin B-3. "
References:
DoctorYourself.com - Niacin Therapy Details
Tryptophan - Wikipedia, the free encyclopedia