Most Americans are doing one nightly activity that's wrecking their sleep, expert says

If you’re not sleeping well, there could be a variety of reasons — but one habit stands out as the biggest culprit.

Dr. Wendy Troxel, a licensed clinical psychologist and senior behavioral scientist at RAND based in Utah, revealed that phone use at night is the activity that is most likely to have a negative effect on slumber.

"Most people are aware of this, but probably the No. 1 habit that's contributing to interrupted sleep, and poor-quality sleep, in Americans is the use of phones at night, particularly in bed," she said in an interview with Fox News Digital.

"About 90% of Americans are using their phones in bed, and as much as I would like to tell everybody to remove the phone entirely from the bedroom, I realize that ship has probably sailed by now."

This disruption is driven by both blue light exposure and the stimulating content on phones, according to Troxel.

"There is blue light emitted from our devices, and blue light can suppress the hormone melatonin, which is the hormone of darkness."

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"But it's not just the blue light that is causing sleep disruptions from our phones. It's really the stimulating content that we're consuming … social media, which is designed to be addictive, so that you can't put that phone down," she added.

This content is also "very emotionally activating," Troxel noted, which is "antithetical to the state we want to be in as we approach sleep."

To counteract attachment to phones, the sleep expert recommends setting a boundary with one simple rule.

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"I recommend that you try to keep your phone more than arms' distance away from you while in bed," she advised. "And set a rule for yourself — if you're going to use the phone, don't do it in bed. In fact, make your feet be on the floor if you're going to use that phone."

Setting this boundary creates "behavioral friction," according to Troxel.

"As a clinical psychologist, I work with people to help them … break habits that aren't serving them," she said. "Having that little bit of behavioral friction makes the habit of immediately grabbing for the phone and scrolling while in bed a little more difficult."

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"And when that automatic behavior is a little more difficult, it's less likely to occur."