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 (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

  • 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 November 2019