Causes and Risk Factors of Insomnia

Insomnia is the most common sleep disorder, affecting about 10% of people. It is characterized by difficulty getting to sleep or difficulty getting back to sleep after waking—in the absence of another sleep disorder. If it occurs at least three nights per week and lasts at least three months, it is called chronic insomnia. There are many potential causes of insomnia, including genetic risk factors as well as common triggers such as lifestyle, diet, exercise, habits, sleep environment characteristics, medications, and coexisting psychiatric and medical disorders. By understanding these causes, it may be possible to resolve your difficulty in sleeping. 

Common Causes

One model to organize the numerous common causes of insomnia was outlined by the psychologist Dr. Arthur Spielman, PhD. He suggested that the contributions could be viewed as predisposing, precipitating, and perpetuating factors. Reviewing the various causes from this viewpoint may help to understand how difficulty sleeping evolves from a few bad nights in a row to unrelenting insomnia.

Predisposing Factors

Your predisposition towards developing insomnia is likely largely based on your genetics, which influences the processes that direct sleep and wakefulness. This can begin early in life: people with idiopathic insomnia can start having trouble in childhood. 

Circadian rhythms can be similarly influenced, usually starting with symptoms in adolescence, leading to a night owl tendency. This condition is called delayed sleep phase syndrome, with trouble getting to sleep (often not falling asleep until 2 a.m.) as well as trouble waking early in the morning. Further evidence of a genetic role includes the fact that insomnia often runs in families, especially for women. 

This predisposition toward insomnia influences both your ability to become sleepy at night as well as your ability to stay awake during the day. Some people always sleep well and never seem to have trouble falling or staying asleep. Others have a high tendency towards developing insomnia, describing themselves as light sleepers. It doesn’t take much to push these latter people past the threshold at which they develop symptoms of insomnia. 

There can be other associated conditions present that may set someone up to later develop insomnia. Anxiety and depression commonly coexist with insomnia. There may be personality factors. Chronic pain may contribute. Various untreated sleep disorders, including sleep apnea and restless legs syndrome, may have a role.

Psychiatric and medical conditions that may predispose towards insomnia, include:

• Depression
• Anxiety
• Post-traumatic stress disorder (PTSD)
• Stroke
• Alzheimer's disease
• Parkinson's disease
• Multiple sclerosis
• Traumatic brain injury
• Asthma
• Sleep apnea
• Heartburn
• Thyroid problems (hyperthyroidism)
• Menopause
• Restless legs syndrome
• Cancer
• Chronic pain

Even before the symptoms of insomnia become apparent, these factors may make it more likely to occur.

Precipitating Factors

Insomnia is often triggered by specific, identifiable conditions. Imagine some situations where you would expect to have trouble falling or staying asleep. These causes can be internal or external. When the precipitating factors are present, insomnia can begin. When thinking back to the start of insomnia, it may not always be possible to identify the initial trigger. Often too much time has passed to recall how it all began.

A common cause of insomnia relates to stress. This can be routine: you have a final examination in school and you don’t sleep well in the nights preceding it. It can be related to major life changes: a lost job, divorce, moving, or the death of a loved one. The demands of life may also cause difficulty sleeping; for example, young children often provoke insomnia and shift workers sleep poorly. Socioeconomic factors also affect sleep: those who are poor have higher rates of difficulty sleeping.

The environment may frequently contribute to poor sleep: light, noise, and temperature all play a role. A lumpy hotel bed, a noisy street, or a hot summer night may disturb sleep. Sleep is best in a cool, quiet, and dimly lit room. If the sleep environment is uncomfortable, or unsafe, this may contribute to insomnia. A bed partner who snores or a child who needs attention at night may make it hard to sleep.

Fortunately, as soon as these triggers resolve, sleep often improves. Once the test passes, you go back to sleeping well again. Returning home from the trip, you sleep well again. In the case of major psychological stress—such as with bereavement—this may take time to improve. This resolution is what usually happens in life. However, sometimes it doesn’t, and insomnia becomes chronic due to perpetuating factors.

Perpetuating Factors

Insomnia becomes chronic when it occurs at least three nights per week for at least three months. It may last for months or even years. Intractable insomnia may persist for decades. This may be due to perpetuating factors.

Your relationship with sleep may change. Sleeping can become a challenge, a source of frustration, anger, and anxiety. These feelings may make it hard to sleep. Even the thought of sleeping or being in your bed may bring up these negative emotions. Waking in the night, which may occur normally, is followed by a check of the alarm clock. You might react to the time on the clock with unhelpful thoughts— calculating the time you have slept or the time left to sleep or feeling frustrated and worrying about what must be accomplished the next day. All of these thoughts may prolong your wakefulness when you want to be sleeping. It may simply not be possible to get back to sleep when waking too close to morning.

The behavior of sleep can also change and undermine the quality of your sleep. You may go to bed earlier or stay in bed later, desperate for any sleep that you can get. You may even try to take naps. By spending too much time in bed, exceeding your sleep needs, you may unintentionally worsen your insomnia. Someone who may only need to sleep seven or eight hours may be spending 10 hours in bed, ensuring two or three hours of wakefulness each night. Poor sleep habits worsen the ability to sleep.

Untreated contributing conditions will also cause insomnia to persist. If you have anxiety or depression that is ignored, your sleep problems will continue. Obstructive sleep apnea frequently causes light sleep and awakenings during the night. These will not resolve until your breathing is improved during sleep. Shift work or jet lag may exacerbate insomnia. The underlying causes of insomnia must be properly addressed in order for insomnia to resolve.

The Role of Arousal

Finally, one component beyond the Spielman model for insomnia that cannot be ignored is the role of arousal. People with insomnia are often more awake, both day and night. Their brains demonstrate increased metabolism, even an increased temperature, with heightened arousal. This activity keeps the person awake during the day: people with insomnia are tired but wired, often unable to take naps if given the opportunity. 

There are also situations when the sympathetic nervous system provokes wakefulness. The system for sleep is overridden by wake-promoting signals. This can be driven by fear or anxiety. This is protective when there are environmental threats. When you feel unsafe to sleep, your brain will keep you awake. No matter the source of these negative or anxious feelings, this same system will promote wakefulness.

Genetics

There are several techniques that have been employed to understand the genetic predisposition towards insomnia, including the study of twins and genome-wide association studies.

One obvious genetic risk factor may be biological sex: women have higher rates of insomnia compared to men.

Circadian disorders, including delayed sleep phase syndrome, often have a familial pattern and genetic predisposition.

More work remains to be done to understand this complex relationship.

It is likely that one gene may influence multiple, often, unrelated traits. For example, some genes may contribute to both insomnia and anxiety, depression, or PTSD.

Multiple genes may work together to create a complex physiological process like sleep. Genes may affect the intrinsic excitability of neurons and lead to overactivity in areas of the brain that promote wakefulness. GABA is a neurotransmitter that inhibits activity in the brain, and one identified gene (RBFOX3) is known to affect this. If that gene is hypoactive, the brain may have difficulty quieting down to promote sleep.

Genes that affect the stress response, and may contribute to hyperarousal, also likely have a role.

Further research is necessary to understand what genetic variations contribute to difficulty sleeping and how this condition manifests.

Lifestyle Risk Factors

Certain lifestyle factors may precipitate insomnia in susceptible individuals. Some of the considerations may include:

Caffeine: If consumed too late in the day, caffeine may contribute to difficulty sleeping. It is found in coffee, tea, soda pop, energy drinks, and chocolate. It may take 4 to 6 hours for half a serving to be metabolized. If you are sensitive to caffeine, it may be best to avoid it after noon—or altogether.

Alcohol: Alcohol contributes to sleepiness due to its interaction with adenosine. It is metabolized fairly quickly, however, and this may fragment sleep. It suppresses deeper sleep stages. It may also contribute to snoring and sleep apnea. Therefore, it is best to avoid alcohol at least several hours before bedtime. 

Nicotine: Smoking may lead to serious sleep disturbances. Nicotine may prolong wakefulness. Nicotine withdrawal can fragment sleep. Smoking may also contribute to irritation of the airway and risks for snoring and sleep apnea.

Recreational drugs: Though sometimes used as a sleep aid due to the effects of cannabinoids to promote relaxation, marijuana also suppresses REM sleep. It may lose its efficacy with time, ultimately failing to improve sleep. Cocaine, methamphetamine, and other illicit drugs are uppers that contribute to insomnia. As these drugs are not well-studied, it is probably best to abstain from all of them, including those like marijuana that purport to serve as sleep aids.

Medications: Stimulant medications that promote wakefulness, including over-the-counter medicines that contain caffeine and prescription treatments for ADHD and hypersomnia, may contribute to insomnia. These include modafinil (Provigil), armodafinil (Nuvigil), methylphenidate, dextroamphetamine, and amphetamine. Steroids are notorious for causing insomnia. Some blood pressure medications (known as beta-blockers) may interfere with melatonin, leading to poor sleep. Review any potential side effects from medications with a prescribing healthcare provider or pharmacist to understand the risks.

Late meals: Food seems to promote wakefulness. Eating too close to bedtime may also contribute to heartburn or reflux symptoms once lying down. Try to allow two hours to elapse between the last meal and bedtime.

Exercise timing: Aerobic exercise—increasing body temperature, heart rate, and blood pressure—may affect the onset of sleep. The body normally cools down overnight with sleep, reaching its minimum several hours prior to the normal wake time. Proper exercise does enhance sleep quality, but the timing may be important. If possible, try to avoid exercising in the last hour of the day.

Resolving Insomnia

In theory, if a cause of insomnia can be properly identified, the condition may be resolved. This may be more or less challenging, depending on the nature of the contribution. It may be helpful to participate in a more structured program to resolve the issues that may be present.

Cognitive behavioral therapy for insomnia (CBTI) can be helpful to track and resolve the potential contributions. The American College of Physicians recommends CBTI as the first-line treatment for chronic insomnia, even before the use of prescription sleeping pills.

CBTI is usually structured as a six-week program that uses sleep logs or wearable health trackers to document sleep habits. Sleep education—including information on sleep needs, homeostatic sleep drive, and circadian rhythms—is presented. Techniques to strengthen sleep are used, including sleep consolidation or sleep restriction, stimulus control, and optimized conditioning. Anxiety and stress are reduced with interventions.

Participation in a CBTI program may be successfully pursued with the help of a sleep psychologist or via shared medical appointment workshops, or online courses. Over time, changes can be made that will enhance sleep and resolve insomnia.

A Word From Verywell

No matter the cause of insomnia, understanding how normal sleep occurs and establishing expectations for sleep can be very helpful. Participation in a CBTI program is highly recommended for individuals who have chronic difficulty sleeping. If difficulties persist, consider evaluation by a board-certified sleep physician.