Serotonin is a vital neuromodulator in social cognitive processes of understanding emotions and intentions. Zamoscik and colleagues at Heidelberg University examined the effect 5-hydroxytryptophan (5-HTP) intake on two social-cognitive tasks, a moral appraisal and an emotion detection task, in a double-blind placebo-controlled study with 77 healthy participants. With 5-HTP, unethical action without repercussions was deemed to be more abhorrent. As people age, their ability to recognize emotions declines, but serotonin precursors can make up for negative emotions. The study suggestedthe usefulness of 5-HTP supplementation to make up for age-related declines in social-cognitive functions.

Zamoscik V, Schmidt SNL, Bravo R, Ugartemendia L, Plieger T, Rodríguez AB, Reuter M, Kirsch P. Tryptophan-enriched diet or 5-hydroxytryptophan supplementation given in a randomized controlled trial impacts social cognition on a neural and behavioral level. Sci Rep. 2021 Nov 4;11(1):21637. doi: 10.1038/s41598-021-01164-y. PMID: 34737364; PMCID: PMC8568973.