Trouble falling or staying asleep usually comes down to one or more overlapping factors: stress, stimulants, screen habits, an uncomfortable sleep environment, or an underlying medical condition. About one-third of the general population reports insomnia symptoms, and 6% to 10% meet the criteria for chronic insomnia. If you’re lying awake wondering what’s going on, you’re far from alone, and the causes are more identifiable than you might think.
Your Stress Hormones Are Still Running
The most common reason people struggle to fall asleep is that their body’s stress system hasn’t wound down. Cortisol, the hormone your body releases in response to stress, normally drops to its lowest levels in the evening. In people with sleep difficulties, cortisol stays elevated, particularly in the evening and the first part of the night. That elevated cortisol doesn’t just make it harder to drift off. It also predicts how many times you’ll wake up during the night, regardless of whether you have a diagnosed sleep disorder.
What makes this especially frustrating is that it feeds on itself. Higher stress hormones fragment your sleep, and fragmented sleep raises your stress hormones further. This vicious cycle can turn a few rough nights into a persistent pattern. The underlying driver isn’t cortisol alone but a broader state of heightened alertness, where the brain’s arousal signals overpower its sleep signals. If you’ve ever felt “tired but wired,” that’s essentially what’s happening at a chemical level.
Caffeine Lasts Longer Than You Think
Caffeine works by blocking the receptors for a molecule called adenosine, which is your brain’s natural sleep pressure signal. Throughout the day, adenosine builds up and gradually makes you feel drowsy. Caffeine plugs into those same receptors without activating them, so the drowsiness signal never arrives even though your body has been accumulating it all day.
The half-life of caffeine is roughly five to six hours in most adults, meaning half the caffeine from a 3 p.m. coffee is still circulating at 8 or 9 p.m. The other half takes another five to six hours after that. So even when you feel like the coffee has “worn off,” a meaningful amount of it is still blocking adenosine at bedtime. If you’re sensitive to caffeine, that afternoon cup could easily be the reason you’re staring at the ceiling.
Alcohol Wrecks the Second Half of Your Night
A drink in the evening can make you fall asleep faster, which is why so many people think of it as a sleep aid. It does act as a mild sedative initially, shortening the time it takes to fall asleep and increasing deep sleep during the first few hours. But once your body processes the alcohol, usually partway through the night, things fall apart.
During the second half of the night, wakefulness and sleep stage transitions increase, resulting in disrupted, shallow sleep. Alcohol also suppresses REM sleep (the dreaming stage, which is critical for memory and emotional processing) in the first half of the night. Once blood alcohol drops, REM sleep rebounds aggressively, often producing vivid or unsettling dreams. The net result is that you might sleep for seven or eight hours after drinking and still wake up feeling unrested.
Screens Delay Your Sleep Clock
Your brain uses light cues to set its internal clock, and the blue light from phones, tablets, and laptops sends a strong “stay awake” signal. Blue light falls in the 400 to 500 nanometer range of the visible spectrum, with wavelengths between 460 and 480 nanometers suppressing melatonin most effectively. That’s the exact wavelength range emitted by LED screens.
The scale of the effect is striking. In one study, two hours of reading on an LED tablet reduced melatonin levels by 55% and delayed the natural onset of melatonin by an average of 1.5 hours compared to reading a printed book under low light. So if your body would normally start producing melatonin at 9:30 p.m., scrolling through your phone could push that to 11 p.m. You’re not just being “distracted” by your phone. Your brain is literally receiving a chemical instruction to stay awake.
Your Bedroom Might Be Too Warm
Your body needs to drop its core temperature by about one to two degrees to initiate sleep. If your bedroom is too warm, this process stalls. The recommended range for adults is 60 to 67°F (15 to 19°C), which feels cooler than most people keep their homes. For babies and toddlers, the ideal range is slightly higher, between 65 and 70°F.
This is one of the simplest fixes for poor sleep, and one of the most overlooked. If your room is above 70°F at night, try lowering it and see if that alone makes a difference. Light bedding, a fan, or cracking a window can all help your body shed heat more efficiently.
Medical Conditions That Disrupt Sleep
Sometimes difficulty sleeping isn’t about habits or environment. It’s a medical issue. Two of the most common sleep-disrupting conditions are obstructive sleep apnea, where your airway partially or fully closes during sleep (causing repeated brief awakenings you may not even remember), and restless legs syndrome.
Restless legs syndrome produces uncomfortable sensations deep within the legs, described as crawling, creeping, pulling, throbbing, or an electric feeling. These sensations typically begin after you’ve been lying down or sitting for an extended time, and they worsen in the evening. The defining feature is an overwhelming urge to move your legs, and movement temporarily relieves the discomfort. Many people with restless legs syndrome also experience involuntary leg twitching and kicking during sleep, which fragments sleep further. If either of these sounds familiar, these are treatable conditions worth discussing with a doctor.
What Actually Helps
Temperature and Timing
Beyond cooling your bedroom, consistency matters. Going to bed and waking up at roughly the same time each day, including weekends, reinforces your circadian rhythm. A warm shower 60 to 90 minutes before bed can also help. It sounds counterintuitive, but the rapid cooling that happens after you step out of the shower accelerates your body’s natural temperature drop.
Cutting Off Stimulants and Screens
Switching to caffeine-free drinks by early afternoon gives your body time to clear the caffeine before bed. For screens, the 55% melatonin reduction from LED exposure is hard to overcome with a blue-light filter alone. Putting devices away an hour before bed, or switching to a physical book or audio content, makes a measurable difference.
Progressive Muscle Relaxation
One popular technique, sometimes called the military sleep method, involves systematically relaxing each muscle group while breathing deeply. You start with your face, relaxing your forehead, cheeks, jaw, and the muscles around your eyes. Then you work down through your neck, shoulders, and arms, letting each area go fully limp before moving to the next. Some people pair this with a visualization, like lying in a dark room in a hammock, or silently repeating “don’t think” for ten seconds to interrupt racing thoughts.
No formal research has tested this specific method, but the components (deep breathing, progressive muscle relaxation, and mental redirection) are well-supported individually. The claim is that with six weeks of consistent practice, most people can fall asleep in under two minutes. Even without hitting that benchmark, the technique gives you something concrete to do instead of lying there anxiously monitoring how long you’ve been awake.
Magnesium
Magnesium plays a role in calming the nervous system, and many people don’t get enough of it through diet alone. In a randomized controlled trial, adults with poor sleep quality who took a daily magnesium supplement for two weeks reported improvements in both sleep quality and mood. Magnesium-rich foods include dark leafy greens, nuts, seeds, and legumes, so dietary changes can help alongside or instead of supplementation.