If you're like most people, you've probably drifted off to sleep as soon as you put on a movie or show at night. Sleep experts told HuffPost there are many reasons this happens.
When you're watching TV at night, you're often in a good sleep environment. "When you wake up in the morning, you develop something called a sleep drive, which is how much your body wants to sleep," said Dr. Neal Walia, a sleep specialist at UCLA Health. "Usually, people are watching movies in the evening after a long workday. This is when their sleep drive is at the highest."
"And then sometimes it's just a lack of stimulation," said Dr. Molly Atwood, at Johns Hopkins Medicine. Watching TV is, generally, a low-stimuli activity. "If you're lying down, it is dark — so your body's kind of getting that signal that it's nighttime and if the movie is not very stimulating, it might be a lot easier for any sleepiness that is there to take over."
"Another big thing is that, especially patients with insomnia, a lot of times what they'll say to me is 'I just can't turn my brain off.' But if you're watching something like a show, you're not really in your own head for the most part," Walia said. Your attention is drawn to the show, not the taxes you still need to do. This encourages your body to drift off to sleep.
Your body's natural circadian rhythm can play a role. "In some circumstances, if you're more of a morning person, your body naturally makes you alert early in the morning and it shuts down alertness early at night," Atwood said.
It's also more common if you re-watch shows. "Our nervous systems are super calm and comforted," Atwood said. You also don't have to pay much attention to the show to know what's going on, which allows your body to drift off easily.
Most people are also sleep-deprived. "A lot of our population is sleep deprived," said Walia. Because of busy days, you may not even notice you're sleepy until you're interacting with something that's low-stimuli. This is when your sleep deprivation can catch up with you.
If you fall asleep during a movie once in a while, there isn't much cause for concern ― but if this is a regular habit, it's worth evaluating your sleep. "If you're sitting upright, the lights are on, it's an engaging movie and you still can't keep yourself awake, that might be more of like, 'OK, I should reevaluate how much sleep I'm getting overall,'" Atwood said.
If you think you're getting enough sleep but still falling asleep during engaging shows, it's worth talking to a sleep specialist. A professional can help test you for underlying conditions that could disrupt your sleep.