Trying to snooze too early could leave you feeling wide awake and frustrated.
On the nights you commit to getting into bed particularly early and scoring eight-plus hours of sleep, you may not get the desired outcome. Once you settle in between your sheets, you might lie there with your eyes wide open for what feels like hours, only to drift off at your usual bedtime — or later.
One potential reason you can’t doze off ahead of schedule: You’re attempting to snooze during the “forbidden zone” for sleep. Here’s what to know.
The Forbidden Zone for Sleep, Explained
Sleep is brought on by a two-process model involving the circadian rhythm (aka your internal body clock, which creates an alerting signal that promotes wakefulness and inhibits sleep) and homeostatic sleep drive (aka sleep “hunger,” which builds up as you spend more time awake), says Cathy Goldstein, M.D., M.S., a professor of neurology at the University of Michigan Sleep Disorders Center. To induce sleep, your homeostatic sleep drive needs to be high and the circadian alerting signals need to decline, she says.
However, approximately four hours before your natural sleep onset (read: the point at which you typically fall asleep), your body encounters the forbidden zone for sleep, says Dr. Goldstein. Also known as the wake maintenance zone, the forbidden zone for sleep is a period in the evening during which your body produces the greatest amount of circadian alerting signal, she explains. When circadian alerting signaling is high, the suprachiasmatic nucleus, a structure located in the hypothalamus that regulates most circadian rhythms in the body, activates your arousal pathways. Simultaneously, your ventral lateral preoptic nucleus — an area of the hypothalamus that controls sleep induction — is inhibited.
“In ‘normal’ circumstances — in the absence of a circadian rhythm or sleep abnormalities/disorders and without significant sleep deprivation — [the forbidden zone for sleep] is going to begin around 7 p.m.,” says Dr. Goldstein. Around 9 p.m., your body will begin to secrete melatonin (a hormone that promotes sleep) in response to dim lighting, and circadian alerting signaling drops, she adds. “This reduction in the circadian alerting signal and elevation of the homeostatic sleep drive will result in drowsiness and, ultimately, the onset of sleep around 11 p.m.,” she says.
The Problem with Going to Bed During the Forbidden Zone for Sleep
By going to bed during your ‘forbidden zone,’ you’ll likely have trouble falling asleep. And consistently hitting the hay during this period can create additional issues over time. “The more you lie in bed awake, the greater you develop an association with the bed and wakefulness, [also known as] conditioned arousal,” says Dr. Goldstein. In other words, snuggling into bed will no longer be a strong cue for sleep, so you’re more likely to feel awake. This may be particularly problematic for individuals with psychophysiological insomnia, says Dr. Goldstein, as the condition may result from the combination of a stressor and a fear of being unable to sleep, according to the Centers for Disease Control and Prevention.
How to Manage Your Forbidden Zone for Sleep
If you truly need to go to bed during your forbidden zone for sleep, you have options. For a long-term solution, you can move this wakeful period up in the evening by shifting your entire circadian rhythm, known as phase advancing, says Dr. Goldstein. To do just that, avoid light in the hours before your natural sleep onset (remember, that’s when your body is naturally ready for sleep) to promote sleepiness and during the first two-thirds of your natural sleep period, she suggests. Then, increase your light exposure in the last third of your natural sleep period to promote wakefulness and during the hours that follow your natural wake-up time, she notes.
For the one-off occasion you want to drift off a bit earlier than usual, start dimming the lights and engaging in relaxing, screen-free activities at the start of your forbidden zone for sleep, suggests Dr. Goldstein. This wind-down period can help your body prepare for the upcoming sleep period, she says. The key: Stay outside the bedroom to prevent conditioned arousal.