Reasons and Causes of Poor Sleep and Insomnia

Difficulty Sleeping May Reflect Your Threshold, Specific Triggers

It is possible to discover some of the reasons, causes, and why insomnia happens
It is possible to discover some of the reasons, causes, and why insomnia happens. Jaris Paul/The Image Bank/Getty Images

There are few things more frustrating than an inability to sleep. Insomnia may undermine your night’s rest, leading to important daytime consequences. Why does insomnia happen? Learn about the factors that may lead to an inability to sleep at night and consider what you might do about these reasons and causes.

Insomnia is defined as the inability to fall or stay asleep or sleep that is unrefreshing in the absence of another sleep disorder (such as sleep apnea).

It is the most common of all the various sleep disorders, and it may be a significant problem in about 1 in 4 people. Nearly everyone has experienced some degree of insomnia, even if only transiently, but why does this occur?

Arthur Spielman’s theoretical model of insomnia underpins our current understanding of the disorder. This theory suggests that three things contribute to the development of chronic insomnia, including: predisposing, precipitating, and perpetuating factors.

Predisposition: The Threshold for Insomnia

It is believed that everyone has the capacity to develop difficult sleeping at night. This predisposition is likely genetically determined. Some of the contributions to it likely include our individual circadian rhythm, homeostatic sleep drive, and level of arousal. The circadian rhythm directs the timing of our sleep, and it may be either advanced or delayed in some people.

The homeostatic sleep drive is dependent on the build of sleep-promoting chemicals, including the compound called adenosine. The longer we stay awake, the sleepier we become, due in part to these chemicals. Finally, the baseline level of arousal also is factored in. Some people are more "wired" – also likely due to varying levels of neurotransmitters that promote wakefulness – and this may make sleep disruption more likely.

The predisposition towards insomnia can be thought of as a threshold. Below the threshold at which insomnia will develop, you sleep fine. Given the proper scenario, however, and the balance tips toward sleep disruption. The things that provoke the development of insomnia are known as the precipitating factors.

The Precipitating Factors for Insomnia

What might cause insomnia? There will be some variability in what provokes insomnia in you. Triggers for insomnia may not be the same for every person. Something that is particularly disruptive to your sleep may have no effect on someone else’s. This varying sensitivity is normal, and it shouldn’t be a source of additional distress.

Some of the most common triggers for insomnia include stress, mood disorders, pain, substance use, and poor sleep environment. Stress of every imaginable type is highly likely to make it difficult to sleep. The night before a big examination or presentation at work may be fitful. Major life events such as moving, the loss of a job, relationship problems including divorce, or the death of a close friend or relative may also lead to insomnia. If these problems lead to anxiety or depression, the risk of insomnia may be compounded.

There are other causes of insomnia as well. In particular, chronic medical conditions, especially those that cause pain, may disrupt sleep. Sleep is usually an anesthetic state, in which pain is not sensed, but nevertheless pain can make it hard to fall asleep. There are certain substances that may contribute to difficulty falling or staying asleep as well. The most common, caffeine, is notorious for sleep disruption. Nicotine is another stimulating substance that disrupts sleep. Alcohol may cause drowsiness initially, but when it starts to wear off, sleep becomes fragmented. Other medications and drugs can also undermine sleep.

Finally, the sleep environment can also make it hard to sleep. If your bedroom is too warm or too cold, too bright, or too noisy, sleep may be fleeting. An uncomfortable bed, or none at all, may also cause insomnia. If someone is snoring nearby, or a baby cries out to be fed, sleep becomes light and fragmented. Studies have also shown that environmental noise, such as may be present in a busy city, can also disrupt sleep.

It should also be noted that working against your natural ability to sleep can also cause insomnia. If you try to sleep at a time that your body expects you to be awake (contradicting your circadian rhythm), you will likely lie awake. If you took a prolonged nap in the afternoon, your desire for sleep will be diminished due to a weakened sleep drive. In addition, if you are wound up after a fight with your spouse (with increased arousal), insomnia will likewise result.

Perpetuating an Inability to Sleep

Once your threshold for insomnia has been crossed, incited by one of the precipitating factors, you will find yourself lying awake at night. This may quickly pass, as occurs in acute insomnia. If you had insomnia due to an examination that has come and gone, for example, the difficulty sleeping goes away with it. However, there are scenarios where insomnia will persist, and unintentional behavioral or cognitive changes may actually make things worse.

If the precipitating factor has not resolved, it is very likely that it will continue to disrupt your sleep. It is possible to adapt to some of these triggers, depending on the nature of the disruption, but this may not always happen. Therefore, it can be important to identify the cause of the insomnia and try to resolve it. This will require a careful self-assessment of the factors that are important to your situation.

Unfortunately, some triggers are not easily remedied. It may require a tincture of time to grieve a death. A mood disorder may require medication or psychotherapy. A new baby may take months to sleep through the night. Focus on what you have control over, and avoid making things worse.

Many people with insomnia unintentionally make their insomnia more sustained. Several bad nights of sleep (or dozens, for that matter) may lead you to change your pattern of sleep. This can be particularly true if you find yourself waking and lying awake in the night. You may think, "I am not sleeping well, so I am going to go to bed earlier to try to get enough sleep." By extending your time in bed, you have introduced a new problem: you are now going to bed earlier than your body wants you to. If your body says you will get sleepy at 11 PM, but you crawl into bed at 9 PM, guess what happens? You will now have trouble falling asleep as well.

There can be a lot of emotions and thoughts that become associated with insomnia. Chronic insomnia is deeply frustrating. Feelings of distress, hopelessness, inadequacy, and failure become part of the scenario. People who sleep well do not wake in the morning and assess how well they slept. Insomniacs often do. Sleep becomes a focus in insomnia, and when it does, it becomes a challenge. There can also be an element of catastrophization, in which the worst possible scenario is imagined during the periods of wakefulness: "If I don’t get enough sleep, I’m going to get fired." Many of these thoughts and feelings must be defused, and cognitive-behavioral therapy for insomnia (CBTi) can be very helpful in this regard.

It is clear that insomnia can happen for multiple reasons, as detailed above. Everyone has a specific threshold at which insomnia will develop. The precipitating factors will vary for each person, but there are common triggers related to stress, mood, pain, and substance use. Acute insomnia becomes chronic when behaviors, thoughts, and emotions change surrounding sleep. If you find yourself stuck in the pattern of insomnia, it can be helpful to speak to a sleep specialist to begin to make changes that can correct the problem. Insomnia can be treated effectively, so reach out to get the help that you need.


Kryger, MH et al. "Principles and Practice of Sleep Medicine." Elsevier, 5th edition. 2011.

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