Do you love waking up with the sun, or do you prefer to stay up late? Your natural preference for sleeping and waking, called your chronotype, isn't just a habit—it's partly decided by your genes! A 2019 study published in the Nature Communications, involving nearly 700,000 people, has given us amazing new information about the genes that control our chronotype and how they might affect our mental and physical health. Everyone falls somewhere on a spectrum: early risers on one end and late sleepers on the other. While things like seasons, where you live, and whether you're in a city can influence your chronotype, studies show that anywhere from 20% to 50% of your chronotype is decided by your genes from birth. Until recently, we didn't know much about these specific genetic factors. Uncovering New Genetic Connections By looking at genetic information from 250,000 people from 23andMe and 450,000 from the UK Biobank, researchers matched their genes to whether they identified as "morning" or "evening" people. Our study found an incredible 351 new genetic variations that help determine a person's chronotype. Before this research, we only knew about 24! Past studies have suggested that night owls might have a higher risk of conditions like obesity, depression, and even type 2 diabetes. Our new discoveries about chronotype genes allowed us to investigate whether staying up and waking later directly causes these health problems. How Your Genes Affect Your Body Clock Your body clock is more than just a timekeeper; it's like an internal manager. It tells your body when to be active, when to feel hungry, and when to release important hormones. Most importantly, it signals when you should feel tired and go to sleep. Some of the genetic changes found were in or near genes that are essential for the proper working of this body clock. This suggests that some of the differences between larks and owls come from small variations in their internal clocks. This could explain why owls often have body clocks that run a bit slower than larks. Even though your body clock can run on its own, it usually runs a little longer than 24 hours. To stay in sync with the actual day and night, it gets clues from your surroundings, like temperature and light levels. These clues help "reset" the clock each day. The researchers also found genetic variations in genes important for the retina, the part of your eye that translates light into signals for your brain. One experiment showed that artificial light at night affected owls' body clocks more than larks'. This might mean that owls' retinas are less effective at sensing and communicating light, making it harder for their clocks to stay in sync. They also identified many other genetic variations that have appeared in studies of other health conditions. These include genes related to insulin levels, appetite, and how quickly your liver breaks down stimulants like nicotine. More research is needed to understand if these variants affect your body clock directly or through other behaviors. Other Ways Genes Affect Our Health This study significantly expanded our knowledge of the genes influencing whether you're a morning person. Many of these newly identified genes are involved in how our internal body clock works. The genes that were linked to being a morning person genuinely influence when you go to sleep and wake up, not just how long or how well you sleep. The research suggests that having a genetic tendency to be a morning person might actually lead to a lower risk of mental health issues like depression and schizophrenia, and generally higher well-being.