5-HTP for sleep and mood: what does the evidence show?

What is 5-HTP?

5-hydroxytryptophan, or 5-HTP, is an intermediate step in the body’s production of serotonin, a chemical messenger with many roles. Some supplements obtain it from Griffonia simplicifolia seeds; the body can also make it from the amino acid tryptophan. Knowing this pathway does not show that extra 5-HTP will correct an individual’s mood or sleep problem. It is not the same substance as serotonin, also called 5-HT.1

Does it help with sleep?

The US National Center for Complementary and Integrative Health says evidence on 5-HTP for insomnia is very limited. Feeling sleepy is not the same as improving chronic insomnia.

In a 2024 Singapore study, 30 older adults completed a 12-week comparison of 5-HTP with no supplement. Researchers reported improvement in some sleep measures, particularly among people who initially slept poorly. The small study had no matching placebo, so expectations may have affected self-reported sleep. The published abstract does not establish long-term safety or a general treatment effect for diagnosed insomnia.

The publisher reports funding from a National University of Singapore programme; the full report was not accessible for complete appraisal on this check. The result needs confirmation. Persistent sleep problems deserve assessment; compare melatonin and sleep.23

What about depression or anxiety?

Some small studies have reported mood changes, but their designs and participants differ. A 2019 review included 13 investigations of 5-HTP in depression. The authors described substantial variation and noted that few used placebo comparisons. The combined findings cannot establish a dependable treatment effect or replace care for a diagnosed condition. The review searched through May 2018; newer research may change the picture. Discuss persistent symptoms with a qualified clinician rather than stopping or replacing prescribed treatment.41

Interactions and serotonin toxicity

Memorial Sloan Kettering advises against using 5-HTP with medicines that affect serotonin, including some antidepressants such as monoamine oxidase inhibitors (MAOIs), without supervision from the treating clinician. It also advises avoiding combinations with St John’s wort or SAM-e. A case report described serotonin syndrome after combining 5-HTP with the antibiotic linezolid. One case cannot tell us how often this occurs, but serotonin toxicity can be serious.

Agitation or confusion, fever, shivering or a rapid heartbeat after a possible interaction need urgent medical assessment. A seizure, collapse, difficulty breathing or inability to wake after a possible poisoning or interaction requires emergency help immediately. Do not stop a prescribed medicine on your own. See supplement and medicine interactions.

Memorial Sloan Kettering also describes a case of a scleroderma-like illness in a person receiving both 5-HTP and carbidopa, with pain and swelling of the hands and feet, rash and weight loss. One case cannot establish how often this happens. If you take carbidopa, discuss 5-HTP with the treating clinician before use.16

Side effects and product uncertainty

Nausea, vomiting and diarrhoea have been reported; headache, insomnia and palpitations are less common. Product contents and other medicines matter. Short trials cannot establish long-term safety. Memorial Sloan Kettering describes an older family case of an eosinophilia–myalgia syndrome-like illness linked to a 5-HTP product containing impurities. This report does not establish the frequency of harm or the contents of products sold today.

Tell a clinician and the laboratory about 5-HTP before testing: it may affect a 5-HIAA urine test used for certain tumours. A label or “natural” origin does not prove a product is suitable for you. For another mood product and its different interaction risks, see St John’s wort.1

Does 5-HTP improve attention or ADHD?

A 2026 UK randomised, placebo-controlled study tested a single administration of 5-HTP in 112 adults with high or low scores on an ADHD-traits questionnaire. Participants completed computer tasks before and after. Researchers found no significant improvement in distractibility with 5-HTP. One working-memory accuracy measure improved with placebo but not with 5-HTP.

A high questionnaire score was not the same as an ADHD diagnosis. People taking ADHD or serotonin-altering medicines were excluded. Eleven participants in the 5-HTP group reported fatigue, nausea or vomiting; adverse events were collected through participant reports rather than a systematic assessment.

The study did not assess everyday functioning, longer use or treatment alongside ADHD medicines. Authors reported no specific funding and no competing interests. It does not establish 5-HTP as an ADHD treatment; a short null result also does not settle every future research question. Discuss attention concerns and treatment changes with a clinician.5