Studies of 5-HTP

Despite the benefits marketed by suppliers of 5-HTP supplements, there are few credible scientific studies of 5-HTP.

However, the results from these studies are promising and suggest that 5-HTP can help with depression, weight loss and sleep.

5-HTP And Depression

At present, 5-HTP an amino acid and precursor to the neurotransmitter serotonin, is under researched compared to SSRI antidepressants which undergo lengthly clinical trials.

5-HTP studies to date have been on a small scale.

The small scale studies comparing the effectiveness of 5-HTP and antidepressants suggest 5-HTP may be just as effective as some SSRI antidepressants prescribed to patients. Unlike 5-HTP, which as a precursor is thought to increase serotonin levels, SSRI antidepressants work by inhibiting the re-uptake of existing serotonin.

A study by Poeldinger et al. (1991)[1] compared the antidepressant effects of 5-HTP with fluvoxamine, a modern antidepressant. Fluvoxamine is commercially branded as 'Luvox'.

Poeldinger's study found that subjects who were given 5-HTP had a slightly better response than those who had fluvoxamine. The study also found that the side effects from 5-HTP were less severe than those who had been given fluvoxamine.

An earlier study by Costa and Greengard(1984) [2] also found positive results with 5-HTP. Subjects were given a dosage of 200mg 5-HTP. The subject group experienced an almost 50 percent fall in depression.

5-HTP And Weight Loss

Another study by Costa and Greengard have shown that subjects given 5-HTP may experience weight loss.

Loss in weight was directly related to the dosage of 5-HTP.

However, 5-HTP may indirectly cause weight loss. At higher doses a loss of appetite can be a side effect of 5-HTP.

5-HTP is also thought to cause the feeling of satiety faster after eating. Thus it is the feeling of satiety not 5-HTP itself which may be responsible for any weight loss.

5-HTP and Sleep

As with weight loss, 5-HTP may indirectly help with sleep [3]. 5-HTP can increase melatonin levels, a hormone produced by the pituitary gland which regulates sleeping and waking cycles.

Please read our precautionary warning on the side effects of 5-HTP.


  1. W. Poeldinger, et al. A Functional-Dimensional Approach to Depression: Serotonin Deficiency as a Target Syndrome in a Comparison of 5 -Hydroxytryptophan and Fluvoxamine. Psychopathology. 1991; 24: 53-81.
  2. Costa and Greengard (1984) Frontiers in Biochemical and Pharmacological Research in Depression. Advances in Biochemical Psychopharmacology Vol. 39 pg. 301-313
  3. Soulairac A, et al. Effect of 5-hydroxytryptophan, a Serotonin Precursor, on Sleep Disorders. Ann Med Psychol. Paris. 1977;1(5):792-98.