Poor sleep is major health concern facing Americans today, and melatonin supplements are one of the most popular sleep aids in the US. Melatonin is an endogenous hormone produced by the pineal gland in the absence of light that affects circadian rhythmicity. Interestingly, the prevalence of the use of melatonin as a sleep aid and the reasons for its use among young adults are unclear. A question also remains regarding the costs and benefits of the use of melatonin supplements in young adults with healthy sleep. The evidence on whether melatonin affects sleep in young individuals with health sleep is mixed, and some studies have shown that melatonin can impair cognition in individuals with healthy sleep. Therefore, my dissertation includes two studies that aim to better elucidate the prevalence and effects of exogenous melatonin in young adults. Study 1 assessed sleep aid use in undergraduates using an online survey. Participants answered a series of questions about their history using sleep aids, including melatonin, diphenhydramine- and doxylamine-based sleep aids, cannabis, and alcohol. We also measured sleep quality, time of day preferences, insomnia severity, anxiety, and depression to assess individual differences in sleep aid use. Melatonin was the most popular sleep aid- over 57% of participants reporting using melatonin at some point in their life, and the top reasons for use were trouble falling asleep and to prepare for an important commitment the following day. Those who reported using melatonin had worse sleep quality, higher insomnia severity, and higher anxiety and depression, and were more evening-oriented, than those who had never used melatonin. Study 2 used an experimental design to investigate the effect of melatonin on sleep and morning cognition in young adults. Participants completed the Psychomotor Vigilance Task (PVT; a measure of attention), the UNRAVEL task (a measure of placekeeping), and the Paired Associates Learning (PAL) test (a measure of declarative memory) in the evening. Participants then took a pill, under double-blind conditions, containing melatonin (5mg or 2mg) or placebo, and received an 8-hour sleep opportunity with polysomnography to measure sleep. One hour after waking, participants completed the tasks again. Results showed that melatonin did not affect sleep, but impaired placekeeping and attention in the morning. Thus, the costs of taking melatonin seem to outweigh the benefits for young adults with healthy sleep. These results also suggest that melatonin may not have sleep-promoting effects in young adults, which could be because melatonin does not promote sleep outside of its effect on circadian timing. Taken together, these two studies suggest a potential disconnect between the expected effects of using melatonin as a sleep aid and the observed effects of melatonin on sleep.
Read
