The pursuit of consistently good sleep can feel endless, but restlessness about what it takes doesn’t have to be.
According to the Centers for Disease Control and Prevention, about one in three U.S. adults reported getting inadequate sleep every day, while nearly half reported falling asleep during the day without meaning to at least once a month. Additionally, 50 to 70 million Americans grapple with a sleep disorder of some kind.
Dr. Matthew Lehrer, assistant professor of psychiatry at the University of Pittsburgh and a member of numerous national sleep science organizations, offers perspective on the state that accounts for about one-third of our lives.
How many hours of sleep does a person need?
Most healthy adults need seven to nine hours per night. That range exists because people genuinely differ. A small number function well on less, though far fewer than the number who believe they do.
The better question is how you feel and function during the day. If you’re logging eight hours and still dragging, something is probably interfering with your sleep quality: a medical condition, stress, a mental health issue, medication, shift work, pregnancy, or ordinary habits.
Age matters, too. Children and teenagers need more sleep because their brains and bodies are still developing. Teenagers also undergo a biological shift toward a later internal clock. Older adults don’t actually need much less sleep — their sleep simply becomes lighter and more fragmented.
What are a few ways to maximize the effectiveness of sleep?
The single most effective thing is consistency: going to bed and waking up at roughly the same times every day, weekends included. A stable schedule stabilizes your internal clock, and a stable clock makes everything else easier.
After that, a handful of habits also have a strong impact:
Get outdoor light soon after waking. Morning light is the strongest signal your body clock uses to anchor itself, and even an overcast sky outdoors is far brighter than any indoor lighting. Exercise regularly, but not so close to bedtime that it leaves you wired.
Keep your bedroom cool, dark and quiet. Somewhere in the mid-60s is ideal for most people.
Reserve the bed for sleep and sex. If you find yourself lying awake for a long stretch, it’s usually better to get up and do something calm than to stay in bed frustrated — which keeps your brain from associating the bed with being awake.
Wind down before bed and ease off screens in the final hour. Dimming the lights and stepping away from stimulating content matters more than any single gadget or filter.
People tend to fixate on what happens at night, but good sleep is built across the whole day, especially through how much light you get and when.
What habits make sleep less effective?
The usual suspects:
Caffeine late in the day. Caffeine has a long half-life, so a coffee at 3 p.m. can still leave roughly half its caffeine in your system by 9 p.m., even if you don’t feel wired. You should also avoid alcohol close to bedtime; nicotine (a stimulant) and heavy meals right before sleep; an irregular sleep schedule; and bright lights from screens late at night.
The one that surprises people most is alcohol. It can help you fall asleep faster, but as your body metabolizes it overnight, your sleep turns lighter and more broken up. You end up with a night that looks fine on the clock but isn’t actually restorative.
What does sleep do for the body and the mind?
Sleep is active maintenance for nearly every system in the body. As you sleep, your brain consolidates memories, processes the day’s information and helps regulate emotions. Sleep also supports immune function, cardiovascular health, metabolism and hormone regulation.
One of the most striking findings from recent research, and an area I study, is that the brain appears to clear metabolic waste more efficiently during deep sleep, including some of the proteins that accumulate in Alzheimer’s disease. In effect, deep sleep may be part of how the brain keeps itself clean over a lifetime. That’s one reason the long-term relationship between sleep and brain health is drawing so much scientific attention.
From a psychiatric standpoint, sleep is one of the foundations of emotional well-being. When we sleep well, we’re better able to manage stress, hold our focus, and keep our mood steady.
What happens when people don’t get enough sleep?
In the short term, too little sleep shows up as irritability, trouble concentrating, slower reactions and poorer judgment, including food cravings. It also makes us more anxious and more emotionally reactive, so small problems start to feel bigger than they are.
Over time, chronic short sleep is linked to a higher risk of depression, cardiovascular disease, obesity, diabetes and weakened immune function.
How helpful is the data provided by sleep tracking? Why does it often tell a different story than how I feel about the previous night’s rest?
Sleep trackers are useful for spotting broad patterns: how consistent your bedtime is, roughly how long you’re sleeping, and how often you’re waking up. Where people over-interpret them is in sleep stages. Consumer devices estimate sleep stages from movement and heart rate rather than directly measuring brain activity, making stage estimates less reliable than clinical sleep studies.
That’s why the tracker and your own sense of the night often disagree. How rested you feel depends on things a wristband can’t measure well, including stress, mood and how refreshed you are on waking.
There’s even a name for the flip side of this — orthosomnia, where people grow so anxious about optimizing their sleep scores that the worry itself starts to hurt their sleep. I tell people to treat tracker data as one source of information, not a verdict. If you wake up feeling good, a low score shouldn’t talk you out of it.
What are your recommendations and warnings on melatonin?
Melatonin is generally safe for short-term use, and it’s genuinely helpful for problems rooted in the timing of your internal clock, such as jet lag, shift work or a sleep schedule that has drifted too late.
The key misunderstanding is that melatonin isn’t a sedative or a traditional sleeping pill. It works more like a timing signal, telling your brain what time it is biologically rather than knocking you out. That also means when you take it and how much matter more than people assume. A small dose at the right time is often more effective than a large one. More is not better, and the very high doses sold over the counter aren’t necessarily doing you any favors.
Melatonin isn’t tightly regulated, and studies have found that the actual amount in a bottle can differ substantially from what’s on the label. Start with the lowest effective dose, and if you’re taking it night after night, talk to a clinician. And if the real driver of your insomnia is anxiety, depression, sleep apnea, or another condition, melatonin won’t address the underlying cause.
How many nights of consecutive inadequate sleep does it take before people begin to see long-term effects? What do those look like and how can they bounce back?
Even a few nights of significantly reduced sleep can measurably impair mood, attention and judgment. The longer-term consequences tend to develop when short sleep becomes a pattern measured in weeks, months and years rather than days. That’s when you see persistent fatigue, elevated stress, higher depression risk and physical health problems.
The encouraging part is that most short-term effects reverse once you return to healthy sleep. One caveat worth knowing is that you can’t fully “bank” or repay sleep the way people hope. While most short-term effects improve once healthy sleep resumes, you can’t fully make up for chronic sleep loss with a weekend of catch-up sleep. A consistent sleep schedule remains the best remedy.
Why do we dream and what can our dreams tell us about how we’re sleeping?
We still don’t have a complete scientific answer for why we dream. Dreaming appears tied to memory processing, emotional regulation and the brain’s activity during sleep. That’s especially the case with REM sleep, when the most vivid dreaming happens.
Dreams can reflect stress, anxiety or emotionally significant experiences, but they aren’t diagnostic tools. Vivid dreams don’t automatically mean you slept better or worse. What dreams really tell us is that sleep is anything but idle. The brain stays remarkably busy overnight, doing the memory and emotional work that helps us function the next day.