5-Methoxy-DL-tryptophan is primarily used in research settings to study the biosynthesis and metabolism of serotonin and melatonin. It serves as a precursor in the synthesis of these neurotransmitters, aiding in the understanding of their roles in sleep regulation, mood stabilization, and circadian rhythms. Additionally, it is employed in the development of pharmacological agents targeting serotonin-related disorders, such as depression, anxiety, and sleep disorders. Its application extends to investigating the effects of altered serotonin levels on neurological and physiological processes.