Endogenous melatonin and impulsivity in humans.

Objectives: This study aimed to examine the relationship between salivary melatonin levels and impulsivity in humans, as the literature has not examined this relationship in healthy individuals.

Methods: We recruited 75 participants aged 18-55 years, measuring their salivary melatonin concentrations using an enzyme immunoassay and their impulsivity using the Barratt Impulsiveness Scale (BIS) scores.

Results: The participants' salivary melatonin levels were positively correlated with impulsivity. With regard to the three main factors of the BIS, melatonin levels were positively correlated with attentional impulsiveness but not with motor impulsiveness or non-planning impulsiveness. Of the six subfactors assessed by the BIS, melatonin levels were positively correlated with attention, motor, and cognitive instability, while negatively correlated with perseverance. They were not correlated with self-control or cognitive complexity.

Conclusion: Individuals exhibiting high melatonin levels are more likely to have impulsive attention and cognitive instability, in addition to lacking perseverance.