Apple’s Night Shift feature, which it says “may help you get a better night’s sleep,” doesn’t appear to live up to its claim, according to new research. Because exposure to blue light affects the regulation of sleep cycles, the hope is that Night Shift, which filters blue light from screens after sunset, will make falling asleep easier. But as a recent study shows, sleep is weird and complicated, and a single phone feature likely won’t do much to combat sleepless nights.

The study, published in Sleep Health, tracked the sleep of 167 young adults for one week. People were divided into three groups: one that used their phones for an hour before bed with Night Shift turned on, one that did the same with Night Shift turned off, and one that didn’t use their phones at all before bed.

“In the whole sample, there were no differences across the three groups,” said Chad Jensen, the lead researcher of the study, in a press release. “Night Shift is not superior to using your phone without Night Shift or even using no phone at all.”

This is only one small study that will need to be replicated at a larger scale with different samplings of people before it can be generalized. Still, the results for the Night Shift feature fall in line with early skepticism about how much it can help sleeplessness, especially because Apple doesn’t specify which wavelengths of light are blocked. And while blue light and phone use do likely contribute to difficulty sleeping, there are many other variables to consider within the complexities of sleep and sleep hygiene.

The researchers were mildly surprised that even the group of people who went phone-less before bed didn’t necessarily have better sleep on average. “Our hypothesis was that we would see better sleep without using the phone across the full sample,” Jensen tells The Verge, “so it was a bit surprising that we didn’t find that.”

Part of that result is likely due to the fact that most of the participants were college students who, according to the researchers, were already sleep-deprived. When people are already very sleepy, it doesn’t really matter if they’re on their phones before bed, says Jensen. “Because your need for sleep is so high at that stage that you fall asleep pretty readily no matter what you do before bed.”

One of the few phone-related differences that the study did observe actually had to do with how much sleep participants got. Of the people in the study who slept more than the roughly seven-hour average sleep time, the people who went phone-less slept better and didn’t wake up as often during the night compared to those who used their phones. But the people who slept less than the average showed no difference in any measures of sleep quality, regardless of whether they used a phone at bedtime or not.

If you are a generally well-rested person, Jensen lists myriad factors that could impact your sleep beyond your phone use: caffeine, exercise, the temperature of the room, the amount of light, the amount of noise, consistency of sleep schedules and bedtime routines, and using the bed for activities besides sleeping. And that’s all before we even consider various sleep disorders that can make people too sleepy or not sleepy enough, even if they strive for good sleep habits.

“Sleep is so individualized, there’s not one thing that works for everyone,” says Raj Dasgupta, a sleep medicine specialist at the University of Southern California. Some people are more sensitive to light and might find blue light filtering helpful, but it won’t be the singular fix that leads to better sleep for everyone.

As far as phones go, there are things to consider besides just blue light exposure, says Jensen. “All those other forms of stimulation that are not related to light are equally important.” If you’re reading a depressing article or laughing at TikToks at bedtime, that level of alertness and engagement will likely hinder your ability to fall asleep, and filtering blue light won’t offset that effect.