Genetics also play a role. In a study published in 2019 in Nature Communications, researchers analyzed data from around 698,000 people and identified hundreds of genetic loci associated with a tendency toward morning activity. This does not mean that our habits are predetermined: age, exposure to light, and the surrounding environment also help shape them. This tendency can change over the course of a lifetime: sleep timing naturally shifts later for many teenagers, while older adults tend to wake earlier. Artificial lighting and daily habits also affect the rhythm of sleep. So simply describing someone as lazy is not enough to explain why they struggle to wake up, just as staying up late does not necessarily mean that someone is naturally a night owl.
