L-tryptophan

L-tryptophan is sold as a «natural sleep aid» on the hypothesis of melatonin synthesis from tryptophan via serotonin. Small 1970s-1980s RCTs showed mild reduction in sleep latency at 1-3 g doses before bed; modern evidence is weak. AASM 2021 and SES 2016 list CBT-I first-line for chronic insomnia; L-tryptophan is in no international sleep guideline. If L-tryptophan was recommended for chronic insomnia instead of CBT-I or workup for sleep apnoea and restless legs syndrome, consider seeking a second opinion. It is also important to check whether the patient takes serotonergic drugs – serotonin syndrome risk.

L-tryptophan supplement is sold as a «natural antidepressant» promising a «safe SSRI alternative». Evidence base in mild-to-moderate depression is insufficient: Cochrane 2002 did not confirm clinically meaningful efficacy. NICE 2022 and SEP 2014 list CBT and SSRIs first-line for mild-to-moderate depression; L-tryptophan is not included. Main risk: self-combination with an antidepressant, tramadol or triptans – serotonin syndrome (tachycardia, hyperthermia, myoclonus, rigidity, confusion). If L-tryptophan was recommended for depression instead of a psychiatric consultation, consider seeking a second opinion.

L-tryptophan is sold as a «natural anxiolytic» on the «tryptophan → serotonin → anxiety reduction» hypothesis. Evidence in anxiety disorders is weak: a significant fraction of tryptophan goes to the kynurenine pathway rather than serotonin, and CNS effect is unpredictable. NICE 2022 and SEP 2014 list SSRIs and CBT first-line for anxiety disorders. Main risk: combination with SSRIs, tramadol or triptans – serotonin syndrome. EMS (eosinophilia-myalgia syndrome) after the 1989 outbreak continues to be reported in isolated cases. If L-tryptophan was recommended for GAD or panic attacks instead of a psychiatric consultation, consider seeking a second opinion.