What Causes Insomnia?

If you’re having trouble sleeping, there can be many potential reasons

Graphic of person in bed suffering from racing thoughts including money, alarm, and weather.
Getty Images / Leo Medrano

As anyone who’s experienced insomnia knows, being awake at night when you’d rather be asleep can be frustrating and stressful: The more you worry about not sleeping, the more awake and stressed you’ll likely feel. And you’re not alone — it’s a situation that’s fairly common, with about 30% of US adults reporting that they have trouble sleeping.

For some, insomnia can be a one-off, but for others, it may be a longer-term issue known as chronic insomnia, defined as having trouble sleeping at least three times a week for at least three months.

However, you can take action before it gets to this point, says Jade Wu, Ph.D., a sleep psychologist at Duke University School of Medicine, Sleep.com advisor, and author of the book, “Hello Sleep.”

“It’s pretty par for the course to spend a week or two in poor sleep if you’re going through a stressful time, adjusting to jet lag, or something like that,” she says. “But if it’s more than a week or two, then it’s probably time to take some concerted effort.” Even though it “technically doesn’t count as chronic insomnia disorder yet,” addressing the situation can help prevent chronic insomnia.

How insomnia can affect you

The repercussions of not getting enough quality sleep are far-reaching. After a night of poor sleep, you’re less alert, which makes it more difficult to concentrate, affects your ability to learn and retain information, and can make it harder to complete tasks. Plus, it means you’re less alert and responsive when you’re behind the wheel: In fact, drowsy driving is behind an estimated 16.5% of fatal car crashes.

Your mood and mental health can also be affected. You’re apt to feel negative emotions more intensely when you haven’t slept well, and have a higher likelihood of experiencing depression, anxiety, and other mood disorders.

Additionally, sleep loss is a contributing factor to poor cardiovascular health, weight gain, and diabetes, and even affects immunity and healing.

What causes insomnia?

There are a number of factors that can cause (or contribute to) your sleeplessness.

Age and stages in life

Being female

Beginning in adolescence, biological females are more likely to experience insomnia. For those who menstruate, the reproductive cycle is often to blame: Premenstrual syndrome and painful periods can both contribute to poor sleep and exacerbated mood issues, which in turn may further impact sleep.

Women are more likely to experience mental health issues, including depression and anxiety, which affect sleep. Post-traumatic stress syndrome (PTSD), which can trigger insomnia, is also more common in women.

Pregnancy or new parenthood

Hormonal and physiological changes during pregnancy can make it hard to fall asleep and may cause middle-of-the-night wakings. While up to 80% of women experience insomnia during pregnancy, fragmented sleep is most likely during the first and third trimesters. Plus, restless leg syndrome and obstructive sleep apnea may occur, especially during the third trimester. Other causes of nighttime wakings include nausea, general discomfort, anxiety, and the need to urinate.

Once the baby arrives, caring for a newborn means frequent awakenings, and parents may find it difficult to drift off to sleep when they head back to bed. Both hypervigilance and anxiety can also lead to fragmented sleep.

Perimenopause or menopause

As menopause approaches, hormonal changes can wreak havoc on sleep. Hot flashes, experienced by up to 80% of women, can cause you to wake up sweating, followed by chills as the hot flash subsides. They typically arrive during perimenopause (which starts about four years before menopause) but persist afterward as well: The average is about 7.4 years, but they can last even longer.

Getting older

As you age, you may find yourself waking up at night more often. Changes to sleep architecture mean less time spent in N3 (deep sleep) and more time in N1 (transition) and N2 (light sleep), which are easier to be awakened from. Additional sleep disruptors include having to wake to use the bathroom, along with aches and pains and potential side effects from medications.

Obstructive sleep apnea, in which airway blockages can prompt multiple awakenings each night, is more likely in older adults. Although sleep apnea is more common in men, the risk for women increases after menopause.

Mental health-related

Mental health issues

Mental health issues, including stress, anxiety, and depression, are all risk factors for insomnia. Plus, there’s a bidirectional relationship, with lack of sleep exacerbating mental health symptoms. In addition to making it difficult to drift off to sleep — anxiety, loneliness, and worrying can prolong middle-of-the-night awakenings.

Hyperarousal or PTSD

If you suffer from post-traumatic stress disorder (PTSD), it’s highly likely that your sleep is affected. “The majority of people with PTSD experience insomnia — difficulty falling and staying asleep,” says Philip Gehrman, Ph.D., professor of clinical psychology at the University of Pennsylvania and clinical psychologist at the Penn Sleep Centers. Many have chronic repetitive nightmares that disrupt sleep as well, he says.

Hyperarousal, which is another common symptom of PTSD, may interfere with sleep and cause frequent wakings as well.

Sleep-schedule related

If you travel frequently for work or regularly work nights, the disruption to your schedule can make it difficult to drift off when it’s time to sleep. That’s because your body’s sleep-wake cycle is governed by your internal circadian rhythms. When you fly to a different time zone — especially one that’s several time zones away — your body clock needs time to catch up. In the interim, you’re likely to experience jet lag due to the mismatch between your internal clock and the new time zone.

A similar mismatch occurs with shift work if you frequently work nights or have a sporadic schedule that requires changes to your sleep.

If your sleep hours are inconsistent, you may experience a condition known as social jet lag. For example, if you sleep late on the weekends to catch up on missed sleep, you may find it harder to fall asleep that night.

Environmental factors

Your sleep environment

The best setup for sleep is one that’s quiet, cool, and dark.

If your sleep environment is noisy, you may have trouble drifting off and may be roused from sleep during the night.

Similarly, if your bedroom is too hot, your sleep is likely to be disrupted.

Light is another sleep disruptor, whether it’s inside (for example, if the TV’s on or there’s other lighting in the room) or seeping in from outside sources such as a street lamp. Additionally, using back-lit tech devices before bed can delay the release of melatonin, making it hard to fall asleep.

Sleep hygiene

What you do during your waking hours can affect how well you sleep. If you nap too long or too late, you may find it harder to fall asleep when bedtime rolls around. Similarly, caffeinated beverages or caffeine pills can alter your sleep by keeping you alert late into the night. Alcohol is another known sleep disruptor: Even though you might fall asleep faster, your overall sleep will be more fitful and will likely include middle-of-the-night awakenings.

Sharing a bed

If your partner has sleep issues, you may have trouble falling asleep or find yourself waking up during the night. “When you have another human in the bed, there’s more opportunity for disruptions,” says Wendy Troxel, Ph.D., a senior behavioral scientist at the RAND Corporation and author of “Sharing the Covers: Every Couple’s Guide to Better Sleep.”

Other health issues


Some medications (either prescription or over-the-counter) can have side effects that impact your sleep. “Stimulants obviously are going to be potentially poor for sleep,” Wu points out, “because they can keep you up if they stay in your system too long.” Other culprits include medications such as mood stabilizers, antidepressants, and anti-anxiety medications that can cause drowsiness during the day. “They may make you take little micro naps or just make you feel poorly during the day so you’re not as active,” Wu explains, “and that causes poor sleep at night.” Some antidepressants can disrupt REM sleep, she adds.

Starting a new medication or weaning off of one can also cause sleep disruptions. “These are definitely prime times for sleep to be thrown off track, but that doesn’t mean the medication is bad for you or that you shouldn’t take it,” she says. “If tapering off of it makes you sleep worse, it just means your body is adjusting to a change.”

Sleep disorders

Obstructive sleep apnea

Although estimates vary, obstructive sleep apnea, which can cause snoring, gasping, and pauses in breathing, affects about 12% of US adults. However, the vast majority remain undiagnosed, according to a report by the American Academy of Sleep Medicine. “Often, people who have sleep apnea have sleep maintenance insomnia, where they just have a much harder time staying asleep,” says Wu. “When they wake up, they stay awake for a long time. And they don’t even know all the times that they wake up.”

Men are generally twice as likely as women to have sleep apnea.

Restless leg syndrome or periodic limb movement disorder

If you’re part of the estimated 10% of the population with restless leg syndrome, which occurs when you’re awake, you may have a related condition, periodic limb movement disorder, that affects your sleep. “If you have pretty significant restless legs in the evenings, chances are you’re also moving your legs a lot throughout the night,” says Wu. Even if the movements don’t fully wake you or keep you awake, they can still affect your sleep quality.

Other medical conditions

Chronic pain

Although chronic pain is a risk factor for insomnia, “it doesn’t have to guarantee insomnia,” says Wu, who notes that traditional approaches to treating insomnia can still be effective. “And if you sleep better,” she adds, “your chronic pain can often get better as well.”


Having attention-deficit hyperactivity disorder (ADHD), which can include racing thoughts and make it difficult to settle down, increases your risk for insomnia. The two conditions often go hand in hand: Up to 80% of adults with ADHD have insomnia. Plus, insomnia can be a side effect of some medications used to treat ADHD.

Cardiovascular disease

Not getting enough sleep is a risk factor for cardiovascular disease, but the relationship goes both ways. Chest pain and shortness of breath can both contribute to poor sleep. “If you have classic cardiovascular risk markers like high blood pressure, that’s going to make it harder to sleep well, and you’re also more likely to have issues such as sleep apnea,” says Wu. Even if you have sleep disturbances that don’t yet meet the threshold for sleep apnea, “little by little, the risk factors affecting your sleep add up,” she points out.

Degenerative diseases

Patients with degenerative diseases are at increased risk for insomnia, which affects about 25% of patients with dementia and about 30% of those with Parkinson’s disease. Sleep disruptions are often linked to circadian rhythm changes, Wu notes: “It’s not just nighttime sleep; it’s that our 24-hour rhythms are less pronounced and are a lot more blunted.”

Treating insomnia

If you have insomnia, there are several steps you can take to address it. In some cases, addressing sleep hygiene aspects can help, as can treating any underlying conditions (such as PTSD or sleep apnea). Overall, the most effective first-line treatment is cognitive behavioral therapy for insomnia (CBT-I), which can help reduce the symptoms of insomnia even in those with underlying medical or psychiatric conditions.