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


The rating system

  • 3 smiliesThese treatments are very useful. They are strongly supported as effective by scientific evidence.
  • 2 smiliesThese treatments are useful. They are supported by scientific evidence as effective, but the evidence is not as strong.
  • 1 smileyThese treatments are promising and may be useful. They have some evidence to support them, but more evidence is needed to be sure they work.
  • No smiley On the available evidence, these treatments do not seem to be effective.
  • Question markThese treatments have not been properly researched. It is not possible to say whether they are useful or not.
  • Exclamation MarkSafety or other concerns have been raised for the use of these treatments.

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 (5-HTP) 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 some studies that have looked at the use of tryptophan and 5-HTP for depression. Generally, these studies have found that tryptophan was more effective than a placebo (dummy pill) at reducing depression symptoms. However, these studies are of poor quality and more research is needed to fully understand whether tryptophan can be helpful in the treatment of depression.

Are there any disadvantages?

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 5-HTP supplements.

Tryptophan and 5-HTP can cause severe side effects if they are taken with other medications including antidepressants. Talk with your doctor or pharmacist if you are thinking of taking tryptophan.

Where do you get it?

In Australia and other countries, tryptophan is restricted. Low dose tryptophan supplements are available over the counter in pharmacies. Higher dose tablets can only be obtained with a doctor’s prescription.


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

  • Kikuchi AM, Tanabe A, Iwahori Y. A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning. Journal of Dietary Supplements. 2021;18(3):316-33.
  • 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.
  • Silber BY, Schmitt JAJ. Effects of tryptophan loading on human cognition, mood, and sleep. Neuroscience and Biobehavioral Reviews. 2010; 34(3):387-407.

Last reviewed and updated: 27 November 2023