What Causes Insomnia?


Written by Dr. Michael Breus

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Insomnia can be caused by a variety of factors, like stress, lifestyle, mental health challenges, illness, or medications. It’s also more common in certain groups than others. Women and people assigned female at birth, older adults, and people with a family history of insomnia are more likely to experience it.

Insomnia is a sleep disorder in which you have trouble falling asleep, staying asleep, or both. Sleep issues occur even when you have the right conditions for sleep. That is, you have time to sleep and a safe space to do it, and it’s still hard to sleep well. 

Insomnia leads to difficulties during the day, too, which can be anything from feeling tired to trouble concentrating to simply being in a bad mood. Overall, insomnia can seriously impact quality of life. 

Insomnia is also common. Anywhere from 30% to 60% of adults have experienced symptoms consistent with insomnia. When it occurs, insomnia can be short-term, lasting only a few days or weeks, or it can be a long-term problem. 

No matter how insomnia shows up for you, you probably want to know why it happens. Understanding the causes behind your sleep problems can be the first step in addressing them and experiencing all the benefits sleep can provide.


Difficulty sleeping because of stress is likely a familiar issue. You might lie awake late into the night worrying about a big work presentation, a loved one’s health, or money troubles. And the more you try to force yourself to fall asleep, the more elusive sleep becomes.

Stress can be a huge contributor to insomnia, and the relationship can be cyclical. Stress in your life might keep you awake, and then your inability to sleep might make you feel even more stressed out. Stress about sleep itself can also build up and make the problem worse. 

When you feel anxious, the brain triggers the release of stress hormones like cortisol. These hormones can provide extra energy to help respond to stress, but elevated cortisol levels, especially at night, have been found in some people with insomnia. 

In many cases, stressful events only provoke brief sleeping problems. When your stress levels recede, sleep may return to normal. However, sometimes short-term insomnia from stress can turn into a longer-lasting problem. 

The way stress impacts your sleep may depend on deep-seated elements of your personality, as certain people are naturally more prone to having their sleep disrupted by stress.

Mental Health

There is a close connection between mental health and sleeping problems. Mental health disorders can lead to insomnia, and insomnia can also cause or exacerbate mental health challenges. 

Around 50% of people with long-lasting insomnia also have a mental health disorder. That can sound overwhelming, but the flip side is that treating one of these problems can often lead to relief from the other.

It helps to look at specific mental health conditions to understand their interplay with sleep.


If you have anxiety, you likely know how it can lead to racing thoughts and persistent worries. These thoughts and feelings may not turn off at night and can keep you awake. People with anxiety disorders also tend to be more susceptible to stress causing disruptions in their sleep. 

What’s more, the lack of sleep from insomnia can make it harder to regulate emotions during the day, which can feed a negative cycle between poor sleep and anxiety.


There is a close relationship between depression and insomnia. Insomnia-like sleeping problems are one of the main symptoms of clinical depression, affecting about 80% of people with depression. 

What’s going on in the brain is complex, but depression is believed to interrupt the body’s normal processes for regulating sleep. Similar to anxiety, persistent thoughts may keep you awake into the night, and disrupted routines may throw off your sleep schedule.

The connection is powerful in the other direction, too, so much so that people with insomnia are as much as two times as likely to develop depression. Despite this, there is strong evidence to suggest that treatment, such as cognitive behavioral therapy for insomnia (CBT-I), can help with insomnia and depression simultaneously.

Substance Use Disorder

Many types of substances disrupt sleep in some way. Alcohol messes with stages of sleep and can make you wake up more easily, especially later in the night. Certain drugs increase levels of dopamine, the “reward” brain chemical, which also causes alertness that may short-circuit sleep. Withdrawal from certain drugs can also interfere with sleep. 

The relationship between substance use and sleep also goes the other way. Sleep deprivation can make it harder to manage emotions and combat cravings, increasing the chances of relapse. That said, treating insomnia and getting better sleep can increase the ability to recover from a substance use disorder.

Post-Traumatic Stress Disorder (PTSD)

It is estimated that over 70% of people with PTSD experience sleeping problems like insomnia. Nightmares, which frequently affect people with PTSD, can cause a fear or avoidance of sleep. 

PTSD also leads to hyperarousal, which basically means the mind and body go into overdrive when reminded of a traumatic episode. Hyperarousal is highly connected to insomnia because it keeps the mind on alert instead of relaxed and ready to fall asleep.

Getting Help for Both Insomnia and Mental Health Conditions

The takeaway when it comes to mental health and insomnia is that it’s important to consider both issues when you talk to your doctor. The two are frequently intertwined, so sometimes treating one can help the other. 

While mental health conditions can contribute to insomnia, they may not be its only cause, especially if sleeping problems evolve over time. As a result, insomnia may require its own treatment plan. 

It may be helpful to talk with your doctor or a mental health professional about the best steps to treat insomnia, including whether to treat it separately. So, for example, if your treatment for anxiety doesn’t help you sleep better, talk to your doctor about what might help with insomnia. 


Lifestyle choices can have a big impact on sleep, and there might be choices in your day that are leading to or worsening insomnia without you even realizing it. The good news is these are relatively simple things to change. 

A variety of factors might come into play here, and maybe more than one of these is to blame for you lying awake late into the night.

  • Too Much Stimulation Before Bed: This can include anything from working late to watching an action-packed TV show right before bed. It can be hard to go straight from something stimulating into sleep. Instead, try something relaxing, like reading a book or journaling.
  • Screen Time: Cell phones, TVs, tablets, and computers all emit a type of light called blue light. Blue light suppresses melatonin, the hormone that tells us it’s time to sleep. 
  • Using Your Bed for More ThanSleep: Ideally, our beds should be reserved just for sleep and sex. If you use your bed for other activities, like watching TV or working, your mind can start to associate bed with these instead of sleep.
  • Caffeine Late in the Day: Coffee and tea in the morning is just fine, but think about switching to decaf after lunch. That’s because it can take up to eight hours for caffeine to stop affecting your brain and body. 
  • Alcohol Close to Bed: Alcohol makes many people drowsy, which is why it may seem like a good way to fall asleep. The problem is that after that initial drowsiness, alcohol disrupts our natural stages of sleep and can lead to fitful sleeping, especially in the second half of the night.
  • Irregular Sleep Schedule: When you go to bed and wake up at very different times every day, simply put, the internal clock in your brain gets confused. That might lead to you feeling tired during the day or tossing and turning at night. Having a regular sleep schedule can help signal to your brain and body that it’s time to go to sleep when you lie down at night.
  • Napping Too Late: Naps can be refreshing when they’re relatively brief and early in the day. Napping too late in the day, though, could mean you’re not tired enough to go to sleep at bedtime.

Injury or Illness

Injury and illness commonly contribute to insomnia. About 40% of people with some sort of medical problem experience chronic insomnia. A medical issue might cause anything from trouble breathing to pain to emotional distress, all of which may make it hard to sleep. 

In this way, insomnia is connected to a variety of medical challenges.

  • Pain: Short-term and chronic pain, especially when it’s widespread, makes it hard to get comfortable during the night and can make it hard to calm the mind. Pain may be caused by a recent injury or a longstanding medical problem.
  • Pulmonary Disease: Lying down at night can make it harder to breathe for people with lung diseases. Medications for pulmonary disease can also cause insomnia.
  • Cancer: Cancer can lead to sleep problems for many reasons, including pain, medication or treatment side effects, and stress. 
  • Diabetes: Having diabetes can lead to trouble sleeping, possibly because of diabetic nerve pain. 

Many other issues that affect hormones, the kidneys, or the digestive or cardiovascular systems can also interfere with normal sleep patterns. 

Unfortunately, sleep is vital to recovering from an injury or illness. That’s why it’s important to talk to your doctor about insomnia so you can get some rest and try to feel better.


What complicates sleep even further is that medications — including those used for many of the health issues already discussed — can cause insomnia. 

The relationship between certain medications and insomnia is complicated, and it depends on the specific drug. In the simplest terms, medications change brain activity, and sometimes a side effect is disrupted sleep. 

There are several different types of medications that are associated with insomnia:

  • Certain antidepressants
  • Respiratory stimulants
  • Some blood pressure drugs
  • Glucocorticoids, which are a type of steroid
  • ADHD medication
  • Over-the-counter drugs to treat congestion and colds

Sometimes sleep can be disturbed when you stop taking a medication. Withdrawal after using a drug for a period of time may provoke changes in brain activity that can temporarily throw off sleep patterns.

Depending on the situation, it may be possible to switch the medication you take, modify the dosage, or change when you take it. The important thing is to talk to your doctor about your sleep challenges while bringing a list of any drugs or supplements that you are taking. In this way, you can help determine if any medications are harming your sleep. 

Insomnia and Other Sleep Disorders

Unfortunately, insomnia can occur at the same time as other sleep disorders. The symptoms can overlap, which sometimes makes it tricky to determine whether insomnia itself or another sleep disorder is the culprit. 

Regardless of the specific diagnosis, several sleep disorders can exacerbate insomnia or contribute to sleep difficulties that closely resemble insomnia. 

Sleep Apnea

Sleep apnea causes a person to briefly stop breathing at multiple points during the night, which can lead to restless and shallow sleep. Sleep apnea is one of the sleep disorders that can go hand in hand with insomnia. As many as 55% of people with sleep apnea have insomnia-like symptoms.

Because sleep apnea and insomnia can have similar symptoms, it is important to talk to a doctor who can review your sleeping problems and overall health. In this conversation, it is essential to mention things that could be symptoms of sleep apnea, such as: 

  • Loud snoring that may be punctuated with choking or snorting sounds, which may first be noticed by a bed partner
  • Morning headaches
  • Dry mouth when you wake up
  • An increased need to urinate during the night

Finding the right diagnosis can help make sure the best treatment is prescribed. For obstructive sleep apnea, this may involve treatment with a CPAP device, which frequently enhances sleep and reduces daytime symptoms. 

Careful collaboration with the doctor can also avoid unwanted side effects of treatment. For example, taking sleeping pills may cause even worse breathing during sleep for people with sleep apnea. Working with the doctor can avoid this kind of complication and identify the best methods to start getting better sleep. 

Shift Work Disorder

Shift work is any work that falls outside of the typical work hours of 7 a.m. to 6 p.m. It can include night shifts as well as evening and early morning shifts. These shifts might be fixed, meaning the same times and days each week, or rotating. Shift work is required for many people, but it can wreak havoc on sleep.

If you’re a shift worker, you’re probably intimately familiar with how an irregular schedule impacts your sleep. You might feel tired at work or have a hard time concentrating. But when your shift is over, and it’s finally time to lie down, you might not be able to fall asleep, especially if it’s daytime. 

That’s because shift work interferes with natural sleep-wake rhythms. Circadian rhythms are 24-hour cycles in our bodies, and they help regulate sleep and wakefulness. This sleep-wake cycle is influenced by environmental cues, like sunlight. When you work at night and try to sleep during the day, this cycle gets thrown off and can cause shift work disorder.

The impact of shift work on sleep depends a lot on the type of schedule you’re on.

  • Rotating Night Work: Rotating night work is perhaps the most difficult type of schedule when it comes to getting quality sleep. Not only are you working when your body naturally wants to sleep, but your schedule is always changing, making it difficult for you to adjust. 
  • Fixed Night Work: While working at night is difficult, being on a fixed work schedule can help you stick to regular sleep times when you’re not working.
  • Early Morning or Evening Work: Working at these times tends to be a bit less disruptive to sleep than a night shift. That’s because you may still get to do the majority of your sleeping during the night. It’s also a little easier to tweak your schedule to get the right amount of sleep.

To cope with the impacts of shift work on sleep, focus on developing some sort of regular  schedule, if you can. For example, even if you work the night shift on a rotating schedule, it may help to request forward-rotating shifts, which get progressively later in the day and are often easier to adapt to.

Restless Legs Syndrome

Another sleep disorder connected with insomnia is restless legs syndrome (RLS). RLS leads to discomfort in the legs. If you have RLS, you often feel tingling or the need to move your limbs, especially while you’re resting. 

Around 85% of people with RLS find that this sensation makes it hard to fall asleep. In addition, even after falling asleep, that uncomfortable tingling might keep waking you up throughout the night.

Though the sleep problems caused by RLS can be frustrating, treating RLS often improves sleep. The choice of treatment for RLS depends on a lot of different factors but might include iron replacement, behavioral changes, or medication.

Working With Your Doctor

As there can be multiple causes of insomnia, it is important to consult with your doctor and discuss any symptoms you are experiencing. They can work with you to find the cause and take steps to resolve your symptoms.


About The Author

Dr. Michael Breus

Clinical Psychologist, Sleep Medicine Expert

Michael Breus, Ph.D is a Diplomate of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine and one of only 168 psychologists to pass the Sleep Medical Specialty Board without going to medical school. He holds a BA in Psychology from Skidmore College, and PhD in Clinical Psychology from The University of Georgia. Dr. Breus has been in private practice as a sleep doctor for nearly 25 years. Dr. Breus is a sought after lecturer and his knowledge is shared daily in major national media worldwide including Today, Dr. Oz, Oprah, and for fourteen years as the sleep expert on WebMD. Dr. Breus is also the bestselling author of The Power of When, The Sleep Doctor’s Diet Plan, Good Night!, and Energize!

  • POSITION: Combination Sleeper
  • TEMPERATURE: Hot Sleeper

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