Very few people make it through life without experiencing a restless night or two. Whether it’s tossing and turning before a big test, feeling wired before an important presentation, or adjusting to a new time zone on the first night of vacation, a rough night is frustrating—but usually forgettable.
For millions of others, however, poor sleep is not a rare disruption but a nightly struggle.
Roughly 30 percent of adults report insomnia symptoms at any given time, and about 10 percent meet the criteria for chronic insomnia disorder.
Because sleep deprivation affects everything from cardiovascular health and immune function to mood regulation, “insomnia really is a 24-hour disorder, not just a nighttime challenge,” explains Wendy Troxel, a senior behavioral sleep scientist at RAND Corporation.
Moreover, a growing body of research shows that the disorder can also become self-perpetuating, as sleeplessness fuels more sleeplessness through the anxiety and stress responses that accompany it.
What insomnia actually is—and isn’t
Clinically, insomnia is not simply not getting enough sleep. “It’s characterized by persistent difficulty falling asleep, staying asleep, or waking too early—along with daytime impairment,” explains Troxel. “That daytime impact is essential to the diagnosis.”
Another key factor is the level of distress the sleep difficulty causes. “If it takes you 30 minutes to fall asleep but it doesn’t bother you, you likely don’t have insomnia,” says Jamie Zeitzer, co-director of Stanford University’s Center for Sleep and Circadian Science. “But if it takes you 10 minutes and it causes anxiety, then you might.” In other words, it is normal for some people to take time to fall asleep, but if you become agitated by how long it takes, it may indicate a problem.
Symptoms of acute (short-term) insomnia “often include daytime fatigue, irritability, and poor concentration, memory problems, and mood disruption,” says Raj Dasgupta, a pulmonary and sleep medicine physician at Huntington Memorial Hospital in California.
Chronic insomnia is different. It includes many of the same symptoms but usually also brings longer-term health consequences.
To be classified as chronic, insomnia symptoms must occur at least three nights a week for three months or longer, “and cannot be explained by another sleep disorder, medical condition, or substance use,” explains Meir Kryger, professor emeritus of medicine at Yale’s School of Medicine and author of The Mystery of Sleep: Why a Good Night’s Rest is Vital to a Better, Healthier Life.
The health consequences of chronic insomnia
Since sleep is one of the body’s most fundamental regulatory systems, persistent disruption can have wide-ranging effects on overall health. “The number one health risk of insomnia is the development of psychiatric disorders, particularly depression and anxiety,” Kryger says.
Longitudinal research supports this. A landmark Johns Hopkins study followed more than a thousand sleep-deprived young men for over three decades and found that insomnia significantly increased their risk of developing clinical depression. Other large studies have reached similar conclusions.
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This association is also why insomnia is increasingly linked with reduced brain health, including impaired cognitive performance and a higher long-term risk of neurodegenerative conditions.
Chronic insomnia is also associated with cardiovascular and metabolic risks, as shown in 2025 research linking it to higher risks of hypertension and coronary heart disease. Other studies have associated insomnia with impaired immune function, increased systemic inflammation, and a greater risk of type 2 diabetes.
Some of these effects occur because “physiologically, the stress system stays overactive as cortisol and sympathetic activity remain elevated when they should quiet down at night,” explains Dasgupta. “In simple terms, insomnia means the body does not fully power off the way it should, which strains multiple systems over time.”
Because sleep deprivation also affects next-day functioning, “insomnia can also cause impaired social, family, occupational, or academic performance as well as increased proneness for errors or accidents,” adds Kryger.
These factors contribute to findings from large cohort studies showing that persistent insomnia is associated with increased mortality risk.
How a bad night turns into a vicious circle
While a sleepless night would theoretically make it easier to sleep the next night, insomnia does not always follow that pattern. “Some individuals experience paradoxical hyperactivity in which the brain tries to compensate for feeling sleepy by overproducing wake-promoting neuromodulators [brain chemicals like norepinephrine that stimulate alertness], which then makes it more difficult to fall asleep the next night,” says Zeitzer.
In other cases, behavioral conditioning or anxiety about sleep itself develops. “Insomnia often becomes a feedback loop driven by physiological and psychological hyperarousal,” Troxel says.
Recent research highlights this self-perpetuating cycle between hyperarousal—which can be measured through brain imaging and cortisol levels, notes Kryger—and insomnia symptoms. People with chronic insomnia often show elevated nighttime brain activity and increased stress-hormone signaling compared to normal sleepers.
Irregular sleep schedules can further disrupt the circadian clock, the body’s internal 24-hour timing system that regulates sleep and wake cycles, Zeitzer explains. This creates a mismatch between biological readiness for sleep and actual bedtime—an effect he compares to jet lag.
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One of the most striking aspects of insomnia research is how strongly the brain learns through repetition and association, to the point where it changes how a person perceives their bed.
“Our brains learn based on paired associations,” Troxel explains. “So, if night after night, you’re awake in bed feeling frustrated, the bed itself becomes associated with wakefulness rather than rest.”
In other words, “insomnia usually starts with stress, but it becomes chronic when the brain learns to associate the bed with frustration or alertness,” says Dasgupta.
This negative association can become very strong. Stuart Quan, a senior physician in the division of sleep and circadian disorders at Mass General Brigham, points to one study showing that 91 percent of individuals with insomnia exhibited anxiety, distress, and maladaptive sleeping beliefs tied specifically to their sleep environment.
Over time, this connection often strengthens and is one reason why “prevalence of chronic insomnia increases with age,” says Kryger.
Breaking the cycle
Insomnia is highly treatable, but the standard approach can seem counterintuitive. “If you can worry less about your insomnia,” Zeitzer says, “it will often go away.”
The gold-standard treatment is Cognitive Behavioral Therapy for Insomnia, a structured, evidence-based approach that targets both behavioral habits and thought patterns that maintain insomnia.
Beyond formal therapy, Kryger emphasizes that establishing healthy sleep habits and maintaining a consistent sleep schedule is essential for those with sleep disorders. “This helps to regulate the circadian rhythm, which is one of the processes that controls sleep,” echoes Troxel.
Listening to the body is also important, with research showing that going to bed only when genuinely sleepy reduces time spent lying awake. “If you cannot fall asleep within a short period of time, get out of bed and go to another room until you feel sleepy again,” advises Quan. This helps retrain the brain to associate the bed only with sleep rather than frustration.
For the same reason, it is important “to use the bedroom only for sleep and for sex,” says Kryger. Research shows that strengthening this association can significantly improve insomnia.
“Having a highly patterned relaxing pre-bedtime routine can also be very helpful,” adds Zeitzer. This includes limiting screen use and stimulating activities before bed, avoiding caffeine late in the day, and adopting calming practices such as meditation or taking a warm bath.
“And be sure to seek medical care,” advises Quan, “when insomnia symptoms have been present for several weeks despite trying simple measures to try and improve sleep.”
