Long gone are the days of having to calculate how many hours of sleep you got last night. Between fitness trackers, downloadable apps, and the health kits that come on our smartphones, pretty much everyone in the modern world has access to sleep data—how long they slept, and how well—right at their fingertips.

But could all that data actually make your sleep worse? That's the implication from a new study published in the Journal of Clinical Sleep Medicine.

Researchers at Rush University highlighted three case studies from their sleep lab, including a 39-year-old man who bought a sleep tracker after having trouble getting a good night's sleep. As soon as he began checking the tracker on his goal of logging at least eight hours of sleep every night, though, he actually started to felt worse than before he had the facts at his fingertips.

Similarly, a 27-year-old woman complained of feeling "unrefreshed" after waking up from what her device said was a poor night's sleep, but, once in a laboratory setting separated from her tracker, she actually sleep soundly and in a state of deep sleep.

“Tracking sleep can become an obsession,” says study author Kelly Glazer Baron, Ph.D., sleep researcher and assistant professor of behavioral sciences at Rush University. “In attempting to reach eight hours every day, people were spending more and more time in bed trying to increase their sleep. The anxiety about not getting enough sleep is enough to keep people up, and by trying to sleep, it’s actually more difficult to relax and fall asleep.”

Baron readily admits trackers are certainly not all bad. And for healthy sleepers, trackers can indeed help raise awareness about sleep, says Jessica Payne, Ph.D., associate professor of psychology who runs the Sleep, Stress, and Memory Lab at the University of Notre Dame, who wasn’t involved in the study. "Just like if you learn that, at the end of the day, you've only walked 5000 steps, finding that you've only slept five or six hours can motivate you to do better the next day," Payne explains. 

It’s when people start obsessing over the data that trackers become counterproductive. And even though this study was small, highlighting only three case studies, but both experts say this anxiety from data is a pattern they see in their clinical practice and research. 

The problem is this: When armed with the most detailed data on your sleep, you start stressing about not getting enough shuteye, which intensifies what Payne calls the “sleep, stress snowball”—the more stressed you are, the less or more poorly you sleep. In turn, the more sleep deprived you are, the more stress your brain and body is under. “That's a powerful negative association that can be difficult to unlearn,” Payne adds. 

What’s more, your sleep is controlled by homeostatic sleep pressure, Baron explains, which basically says the longer you’re awake, the sleepier you are. Contrarily, the longer someone spends in bed attempting to snooze (which often happens with insomniacs), the more people have difficulty falling asleep, the more frequently they wake up, and the harder of a time they have getting back to dreamland.

If you love your tracker, we’re certainly not saying toss it aside. After all, we hear countless stories about guys who didn’t realize they were in that health- and hormone-compromising zone of under six hours a night until they started checking a tracker. 

But take sleep data with a grain of salt, because, in reality, it’s not steadfastly reliable. “I've tried most trackers and wear one myself," Baron says. "I find the data to be motivating for my sleep and steps—they just aren't very accurate about measuring sleep." She’s seen trackers err by up to 45 minutes when compared to lab measurements.

It’s really the focus on a specific number that’s most often at blame for sleep trackers screwing with people’s sleep, Baron says. “Don't fixate on making it perfect each day—instead, look for the overall trend toward a consistent sleep schedule," she says.

Put another way: “If sleep is something someone is worried about in an anxious sort of way, I don't recommend tracking sleep, but rather seeking our professional help, especially if you have insomnia,” Payne says. “However, if sleep is slipping simply because someone isn't prioritizing it, trackers can help.”