Our rating
 Question mark: not recommended as a treatment for depression because of concerns about safety and effectiveness. .

What is it?

Tryptophan is an amino acid. It is not made naturally in the body, which means that humans have to get the tryptophan they need from their diet. Protein is a natural source of tryptophan and other amino acids.

How does it work?

The body converts tryptophan from food into 5-hydroxytryptophan (5HTP) and then into serotonin. Serotonin is a natural chemical messenger in the brain. It is thought that increasing serotonin can be helpful in depression.

Is it effective?

There are many poor quality studies on the use of tryptophan and 5HTP in depression. More studies of better quality are needed.

One study of 10 people found that tryptophan or 5HTP increased mood compared to a dummy pill (placebo). However, the results do not provide enough evidence to say whether tryptophan or 5HTP is effective more broadly.

Are there any disadvantages?

During studies some people have reported nausea, dizziness and diarrhoea from the use of tryptophan.

In 1989 one brand of tryptophan was thought to be the cause of a serious illness (Eosinophilia-Myalgia Syndrome). If you would like further information, please read the United States Food and Drug Administration information paper. Concerns have also been raised about possibly harmful impurities in 5HTP supplements.

Tryptophan and 5HTP can cause severe side effects if they are taken with other medications including anti-depressants. Talk with your health care professional if you are thinking of taking tryptophan.

Where do you get it?

In Australia and other countries, tryptophan is restricted. Low dose tablets of tryptophan are available over the counter in pharmacies. Higher dose tablets can only be obtained with a doctor’s prescription. 5HTP is available in pharmacies, health food stores and online.


The use of tryptophan or 5HTP to treat depression is not recommended as a treatment for depression because of concerns about safety and effectiveness. 

Key references

  • Levitan RD, Shen JH, Jindal R, Driver HS, Kennedy SH, Shapiro CM. Preliminary randomized double-blind placebo-controlled trial of tryptophan combined with fluoxetine to treat major depressive disorder: antidepressant and hypnotic effects. Journal of Psychiatry & Neuroscience. 2000; 25(4):337-46.
  • Shaw K, Turner J, & Del Mar C. Tryptophan and 5-hydroxytryptophan for depression. (Cochrane Database Systematic Review). In: The Cochrane Library, Issue 3, 2009. Published by John Wiley & Sons, Ltd.
  • Shaw K, Turner J, Del Mar C. Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysis. Australian & New Zealand Journal of Psychiatry. 2002; 36(4):488-91.

Last reviewed and updated: 1 December 2016