Struggling to sleep usually comes down to one or more overlapping factors: your body is too alert, your environment is working against you, or a habit you don’t think twice about is quietly disrupting your sleep cycle. The good news is that most of these causes are identifiable and fixable. Here’s what’s likely going on.
Your Body Stays on High Alert
The most common reason people struggle to fall asleep is hyperarousal, a state where your mind and body remain revved up even when you’re exhausted. Stress hormones like cortisol, which normally peak in the morning and taper off at night, can stay elevated if you’re under chronic stress. This keeps your heart rate slightly raised, your muscles tense, and your brain scanning for threats instead of winding down.
Acute stressors, like a job loss, a move, or a health scare, can trigger the first few bad nights. But what often turns a rough patch into an ongoing problem is what happens next. You start worrying about sleep itself. You lie in bed longer trying to force it. You check the clock and calculate how few hours you have left. This rumination creates learned associations between your bed and wakefulness, which ramps up arousal even further. Your brain essentially begins treating bedtime as a stressful event, making the problem self-reinforcing.
Elevated stress hormones also reduce the amount of deep, restorative sleep you get even when you do fall asleep. So you wake up feeling unrefreshed, which feeds more anxiety about the next night.
Screens and Light Exposure
Your body relies on a hormone called melatonin to signal that it’s time to sleep. Light suppresses melatonin production, and short-wavelength blue light (between 446 and 477 nanometers) does so most aggressively. That wavelength is exactly what your phone, tablet, and laptop screens emit. Research published in the Journal of Applied Physiology found that blue LED light causes a dose-dependent suppression of melatonin, meaning the brighter and longer the exposure, the more your sleep signal gets delayed.
It’s not just the light itself. Scrolling social media or responding to messages keeps your brain in an active, problem-solving state right up until the moment you close your eyes. That cognitive stimulation makes it harder to transition into the quieter mental state sleep requires.
Your Bedroom Temperature Matters More Than You Think
Falling asleep requires your core body temperature to drop slightly. If your bedroom is too warm, this natural cooling process stalls, and sleep onset gets delayed. The ideal range for most adults is 60 to 67°F (15 to 19°C). That feels cooler than most people expect, but thermoregulation plays a direct role in reaching and staying in the deeper, more restorative stages of sleep. A room that’s too hot doesn’t just make you uncomfortable; it actively disrupts the biological process your body uses to initiate sleep.
Caffeine Lingers Longer Than You’d Expect
Caffeine has a half-life of three to six hours, meaning that half the caffeine from your afternoon coffee is still circulating in your bloodstream well into the evening. A 2024 randomized clinical trial published in the journal SLEEP found that a single 100 mg dose of caffeine (roughly one small cup of coffee) can be consumed up to four hours before bed without major disruption. But 400 mg, the equivalent of a large coffee or two medium ones, should not be consumed within 12 hours of bedtime. If you’re having a big coffee at 2 p.m. and trying to sleep at 10 p.m., that’s likely part of the problem.
Many people build caffeine tolerance and assume it no longer affects their sleep. But caffeine can reduce deep sleep and increase nighttime awakenings even when you feel like you fell asleep fine.
Sleep Apnea and Other Physical Causes
If you wake up multiple times during the night, feel exhausted despite spending enough hours in bed, or have been told you snore, obstructive sleep apnea may be the issue. Common symptoms include breathing pauses during sleep (often noticed by a partner), waking up feeling short of breath or choking, morning headaches, night sweats, and persistent daytime fatigue. Mood changes like depression and anxiety frequently accompany it as well.
Restless leg syndrome is another physical cause that’s easy to overlook. It creates an uncomfortable urge to move your legs, especially in the evening, making it difficult to relax into sleep. One frequently missed contributor is low iron. Harvard Health recommends checking your ferritin level (a measure of iron stores), because symptoms often worsen when ferritin drops to 50 micrograms per liter or below. In many cases, simply increasing iron intake through food or supplements can significantly reduce symptoms.
How Sleep Changes With Age
If you’re over 50 or 60 and finding sleep harder than it used to be, that’s partly biology. As you age, less time is spent in deep, dreamless sleep, and you wake up more often during the night. Older adults wake an average of three to four times per night. Total sleep time doesn’t necessarily decrease much (most older adults still get 6.5 to 7 hours), but because sleep becomes lighter and more fragmented, it can feel like you’re barely sleeping at all. Many people in this age group also start falling asleep earlier and waking earlier, a natural shift in the body’s internal clock.
When Trouble Sleeping Becomes Insomnia
Everyone has bad nights. The clinical threshold for insomnia disorder is difficulty falling asleep, staying asleep, or waking too early at least three nights per week for three months or longer, combined with real daytime consequences like impaired concentration, mood problems, or fatigue. If that describes your situation, what started as a temporary issue has likely become a pattern reinforced by the anxiety and behavioral habits discussed above.
The most effective treatment for chronic insomnia is a structured approach called cognitive behavioral therapy for insomnia, often abbreviated CBT-I. It works by breaking the cycle of bedtime anxiety and retraining the associations your brain has built between your bed and wakefulness. It typically involves limiting time in bed to match actual sleep time, maintaining a consistent wake time regardless of how the night went, and identifying the thought patterns that fuel nighttime arousal. Most people see improvement within four to eight weeks.
Practical Changes That Help
The factors above tend to cluster together. You’re stressed, so you scroll your phone in bed, which suppresses melatonin, which makes you lie awake longer, which makes you more anxious about sleep. Breaking even one link in that chain can improve things noticeably.
- Keep your bedroom cool. Aim for 60 to 67°F. If you can’t control the thermostat, a fan or lighter bedding can help.
- Set a caffeine cutoff. Stop at noon if you’re a heavy coffee drinker. If you drink one cup, four hours before bed is the minimum buffer.
- Dim screens an hour before bed. Night mode filters help somewhat, but putting the phone in another room eliminates both the light and the cognitive stimulation.
- Get out of bed if you can’t sleep. Lying awake for more than 20 minutes strengthens the mental link between your bed and frustration. Move to a dim room, do something quiet, and return when you feel sleepy.
- Wake up at the same time every day. This is more important than your bedtime. A consistent wake time anchors your circadian rhythm and builds up enough sleep pressure to help you fall asleep the following night.