Now, one major caveat of this study’s findings is that the results were recorded in 188 Berlin patients who were suffering from sleep disorders — although none of them were taking any sleep medications to help them sleep. So these weren’t your typical sleepers.

But the team of scientists from the Charité Medical University of Berlin who recruited these patients and tracked their sleep throughout the year noted that, while the sleep disorders could potentially affect the results, this data is still valuable. And that’s because it comes from people being evaluated in a special sleep lab that monitored the quality, length and type of sleep these folks were getting, which can be more reliable data than someone self-reporting how well or how long they think they slept. What’s more, the fact that these subjects were under observation for sleep disorders meant that researchers were working with a large study group evenly spread throughout the year, which allowed the scientists to investigate any month-to-month differences in sleep. 

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Still, the researchers cautioned in their report that this study should be replicated with “a large cohort of healthy subjects.” And they noted that seasonal changes in sleep may be even greater among people with no sleep problems. 

“Seasonality is ubiquitous in any living being on this planet,” said Dr. Dieter Kunz, the corresponding author of the study, in a statement. 

Also interesting was that, even though these subjects were living in an urban area with low natural light exposure and high light pollution, their sleep patterns still changed with the seasons. 

Kunz, who is based at the Clinic of Sleep & Chronomedicine at the St. Hedwig Hospital, Berlin, suggested that the “sensation of ‘running-on-empty’ in February or March” that many people feel could stem from the fact that “over the winter, human physiology is down-regulated.” 

There’s more research to suggest that our circadian rhythms — aka our internal body clocks, which are affected by changing sunlight — are telling us to catch more Zs as the days get shorter and darker in winter.

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More than one in three (34%) U.S. adults surveyed by the American Academy of Sleep Medicine also reported sleeping more in winter. On the flip side, more than a third (36%) said that they sleep less than usual in the summer. 

“The shorter days during the winter create a great, natural opportunity to spend more time sleeping,” said AASM President Dr. Kelly A. Carden in a statement. 

Data from the National Sleep Foundation also finds that healthy adults tend to sleep 1.75 to 2.5 hours more during the winter. And a new NSF survey of 1,250 adults released in January found that heavy snow also seems to get people snuggling in bed longer. In fact, people added an extra 10 minutes of sleep on average during heavy snowfall. And those in areas getting two feet of snow or more reported snoozing for an extra 18 minutes. 

“Heavy snow, like heavy rain, may trigger some tendency to sleep in and stay in,” Dr. Alex Dimitriu, founder of Menlo Park Psychiatry & Sleep Medicine in Menlo Park, Calif., told the NSF. “[But] this has not been fully studied.”

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The American Academy of Sleep Medicine also has some tips to help you get your best sleep the rest of this winter. 

• Set a bedtime that gives you enough sleep — which is between seven to nine hours for adults ages 18 to 64, and seven to eight hours for adults over 65. An individual’s sleep needs may vary, but you should wake up feeling refreshed and alert. The AASM has an online bedtime calculator to help you pick the right bedtime.

• Step away from screens. Don’t binge on entertainment activities before bed, especially things like watching movies, checking social media or playing videogames, which involve screens or electronics. Too much exposure to light at night can disrupt your circadian rhythm and sleep cycle. 

• Kick that 3 p.m. coffee habit and skip the nightcap. Don’t have caffeine after lunch, and avoid alcohol near bedtime, as both can disrupt sleep.

• Create a wind-down ritual. Treat yourself before bed in scientifically proven ways to help you relax, such as taking a warm bath, sipping tea, journaling or meditating.

• Keep your sleeping space cozy. Make sure that your bedroom is quiet, dark and a little cool — it should remind you of a cave.