5-hydroxytryptophan (5-HTP) can be converted to serotonin in the body. It is often used for depression. It has less evidence for insomnia and anxiety.
5-HTP is a chemical byproduct of the protein building block L-tryptophan. It is produced commercially from the seeds of an African plant known as Griffonia simplicifolia. 5-HTP works in the brain and central nervous system by increasing the production of the chemical serotonin. Serotonin can affect sleep, appetite, temperature, sexual behavior, and pain sensation.
Since 5-HTP increases serotonin levels, it is used for conditions in which serotonin is believed to play an important role. These include depression, anxiety, and many other conditions, but there is no good scientific evidence to support most of these uses.