Genetic Markers of Sleep and Sleepiness.

The circadian clock interacts with the sleep homeostatic drive in humans. Chronotype and sleep parameters show substantial heritability, underscoring a genetic component to these measures. This article reviews the genetic underpinnings of chronotype and of sleep, including sleepiness, sleep quality and latency, and sleep timing and duration in healthy adult sleepers, drawing on candidate gene and genome-wide association studies. Notably, both circadian and noncircadian genes associate with individual differences in chronotype and in sleep parameters. The article concludes with a brief discussion of future research directions.