It's not uncommon to roll out of bed on Monday morning—and, okay, Tuesday, and maybe also Wednesday—half in a dream, wishing it was still the weekend. That feeling is called "social jet lag," and researchers have argued that it's caused by a combination of too much time indoors exposed to artificial light, combined with both staying up and waking up late. These factors delay your body's production of melatonin, the hormone that regulates your internal clock.
Happily, all it might take is a couple of relaxing days outdoors to put your sleep schedule back on track, according to a new study published today in the journal Current Biology.
Scientists at the University of Colorado sent nine volunteers to go camping in tents for one weekend last summer. During the day, they hiked or hung around the campsite, and they were allowed to go to sleep or wake up whenever they wanted. After their trip, the scientists took saliva samples to compare how levels of the sleep hormone melatonin rose and fell throughout the day from before they went camping to afterward.
The campers went to sleep an average of one hour and 48 minutes earlier than people who didn't go camping, and they woke up 90 minutes earlier in the morning. The times when melatonin kicked in also shifted after sleeping outdoors, starting almost 90 minutes earlier when they bedded down in their tents compared to when they were home during the week. For the group that didn't go camping, melatonin production started almost an hour later on weekends compared to the work week.
"Too little natural light during the day and exposure to electrical light at night are the two primary factors contributing to later timing of people's internal clocks," says Kenneth Wright, a professor of psychology at the University of Colorado Boulder and author of the study.
You might be thinking, "What if I like staying up late and sleeping in on weekends?" As it turns out, those late nights can add up to serious health issues. Research shows that when your shifting sleep schedule isn't aligned with your body's internal clock, the havoc it wreaks on your hormones increases your risk of depression, diabetes, and obesity. Plus you're just plain tired all the time, which means your performance at work suffers, and you make poorer decisions while driving.
The same team of researchers had previously tested out a full week of summer camping and found similar benefits, but if you don't have that kind of time off, there's a shortcut: They estimate that the weekend of camping was enough to provide around 69 percent of the benefit of a full week outdoors.
Using a small wrist-mounted light sensor, researchers determined that over the course of the day, campers were exposed to four times the total amount of light than they normally experienced at home. If that sounds like a lot, during a separate camping trip in winter, they soaked up 13 times as much light. All that light tells your body when to wake up, and the pitch blackness in the evening informs when you should be asleep.
Simply opening up your curtains or going for a short jog outside probably isn't enough to keep your body clock synchronized. "The intensity of light outside is much brighter than typical indoor lighting and brighter light has a stronger impact on our clock," Wright says. But when you're up late watching TV at home or out at a bar, the artificial light tells your body that it's still daytime, quashing your melatonin production.
Once you've been camping, however, your body will naturally line up with sunrise and sunset. The trick is to stick to that schedule; otherwise you'll slip back into your old routine of social jet lag. "If people were to go back to their modern environment and not change their exposure to light, then we would expect their clock to be later in a matter of days to a week," Wright says.
When camping, Wright recommends tracking the times you wake up and go to sleep, and then set your alarm to match those times once you're home. Around sunset, turn off some of the excess lights in your home and dim the rest. And when you find yourself dragging a few Mondays in a row, you'll know that your internal reset button might be just a trailhead away.