Trouble sleeping usually comes down to one of a few culprits: stress keeping your brain wired at night, habits that interfere with your body’s sleep signals, an uncomfortable sleep environment, or an underlying health condition you may not have identified yet. Most adults need seven or more hours of sleep per night, but roughly a third of Americans regularly fall short. The good news is that once you identify what’s disrupting your sleep, most causes are fixable.
Your Brain May Be Too Activated to Sleep
The most common reason people struggle to fall or stay asleep is what sleep researchers call hyperarousal. When you’re stressed, anxious, or emotionally wound up, your body’s stress response system increases its output of cortisol, the hormone that keeps you alert. This happens not just during waking hours but continues into the night, raising your heart rate and keeping your nervous system in a state that’s fundamentally incompatible with sleep.
This isn’t just about having a stressful day. Chronic stress can recalibrate your baseline arousal level so that your body stays revved up even when nothing acutely stressful is happening. Almost all scientific models of insomnia point to persistent hyperarousal on cognitive, emotional, and physiological levels as the central problem. That’s why you can feel exhausted and still lie awake: your body is tired, but your brain hasn’t gotten the signal that it’s safe to power down.
Depression also disrupts sleep in a different pattern. People with depression often wake too early and can’t fall back asleep, or they sleep excessively but never feel rested. If your sleep problems started around the same time as persistent low mood, loss of interest in things you used to enjoy, or difficulty concentrating, the sleep issue and the mood issue are likely connected.
Caffeine and Alcohol Are Common Saboteurs
Caffeine has a half-life of three to six hours, meaning half the caffeine from your afternoon coffee is still circulating in your bloodstream well into the evening. A 2024 clinical trial found that a single large dose of caffeine (400 mg, roughly the amount in two strong coffees) can measurably disrupt sleep even when consumed 12 hours before bedtime. A smaller dose of about 100 mg, equivalent to one cup, was safe up to four hours before bed. If you’re sensitive to caffeine, that window may need to be even wider.
Alcohol is trickier because it actually helps you fall asleep faster. It acts as a sedative in the first half of the night, increasing deep sleep and suppressing dreaming sleep. But as your body processes the alcohol during the second half of the night, the effect reverses. You spend more time in light sleep, wake up more frequently, and your dreaming sleep rebounds in fragmented bursts. The net result is that even a moderate amount of alcohol traded a decent first few hours for a terrible second half of the night, leaving you feeling unrested in the morning.
Your Bedroom Might Be Working Against You
Your body needs to drop its core temperature slightly to initiate and maintain sleep. A room that’s too warm interferes with this process directly. The Cleveland Clinic recommends keeping your bedroom between 60 and 67°F (15 to 19°C), a range that supports stable dreaming sleep throughout the night. Many people keep their bedrooms several degrees warmer than this without realizing it’s costing them sleep quality.
Light exposure matters too, especially blue-spectrum light from phones, tablets, and laptops. This type of light suppresses your body’s production of the hormone that signals nighttime, effectively telling your brain it’s still daytime. Even relatively brief exposure in the hour before bed can delay sleep onset by 20 to 30 minutes. If you’re scrolling your phone in bed and wondering why you can’t fall asleep, that’s a direct cause-and-effect relationship.
A Sleep Disorder Could Be the Cause
If you’ve addressed the obvious lifestyle factors and still can’t sleep well, a medical condition may be involved. Sleep apnea is one of the most underdiagnosed sleep disorders. It causes repeated pauses in breathing during the night, and the hallmark symptoms include loud snoring, gasping for air during sleep, waking with a dry mouth, and morning headaches. Many people with sleep apnea don’t know they have it because the breathing interruptions happen while they’re unconscious. A bed partner noticing pauses in your breathing is one of the most reliable early indicators. Diagnosis requires a sleep study, either in a lab or with an at-home device.
Restless legs syndrome is another common disruptor. It creates an uncomfortable urge to move your legs, particularly when you’re lying still, making it difficult to fall asleep. The sensation is often described as crawling, tingling, or aching deep in the legs, and it temporarily improves with movement.
Hormonal changes can also play a role. Perimenopause and menopause frequently cause sleep disruption through night sweats and hot flashes. Thyroid disorders, both overactive and underactive, alter sleep patterns. And chronic pain conditions of any kind make it harder to get comfortable and stay asleep through the night.
How Sleep Cycles Explain Nighttime Waking
Sleep isn’t a single uniform state. Your brain cycles through distinct stages every 80 to 100 minutes, moving from light sleep into deep sleep and then into dreaming (REM) sleep before starting the cycle again. You typically complete four to six of these cycles per night. Brief awakenings between cycles are normal and happen to everyone, but most people don’t remember them because they fall back asleep within seconds.
When something disrupts this process, whether it’s stress hormones, alcohol, a breathing obstruction, or a too-warm room, those between-cycle awakenings become longer and more conscious. You check the clock, start thinking, and the wakefulness feeds on itself. Understanding that brief wake-ups are a normal part of sleep architecture can actually help reduce the anxiety that keeps you awake longer during those moments.
What Actually Fixes the Problem
The most effective treatment for chronic insomnia is cognitive behavioral therapy for insomnia, known as CBT-I. It works by retraining both your habits and your thought patterns around sleep. A recent clinical trial of 155 adults with chronic insomnia compared CBT-I (delivered digitally), sleep medication, and a combination of both. Combination therapy had the highest response rate at 81%, compared to 57% for medication alone. But what makes CBT-I especially valuable is that its benefits persist after you stop the program, while the benefits of sleep medication typically end when you stop taking it.
CBT-I includes several components you can start applying on your own. Sleep restriction, counterintuitively, involves limiting the time you spend in bed to match the time you actually sleep, which builds up stronger sleep pressure. Stimulus control means using your bed only for sleep (and sex), so your brain associates the bed with sleeping rather than lying awake. And cognitive restructuring helps you identify and replace the anxious thoughts about sleep that fuel the cycle (“If I don’t fall asleep in the next 20 minutes, tomorrow will be ruined”).
Beyond CBT-I, consistent sleep and wake times are one of the most powerful tools available. Your body’s internal clock relies on regularity. Waking at the same time every day, including weekends, reinforces your circadian rhythm and makes falling asleep at night easier within a week or two. Morning light exposure, ideally natural sunlight within 30 minutes of waking, further anchors this rhythm. A consistent wind-down routine of 30 to 60 minutes before bed, with dim lighting and no screens, gives your brain the transition period it needs to shift from waking mode to sleep mode.