What is Insomnia? (Types and Causes)

Insomnia is the most common sleep disorder in adults. It has a significant impact on both life expectancy and quality of life, as this sleep disorder lays the groundwork for hosting major health problems as well as social or economic burdens later, if left untreated. 

What's more, untreated insomnia leads to serious problems with sleep deprivation, a health concern considered our largest public health threat in the US by the Centers for Disease Control (CDC).

Diagnosing insomnia accurately is fundamental to finding the best treatments for it so people can move forward with their lives.


What is Insomnia?

Simply put, it describes situations in which, even with the best opportunities and circumstances for sleep, you still have persistent difficulty with:

... all of which lead to some sort of disabling daytime impact (excessive daytime sleepiness, inability to be productive at work, increase in car accidents, depressive disorder, as examples).

Insomnia used to be defined in even more specific terms, but a recent 3rd edition update to the sleep medicine master catalog, the International Classification of Sleep Disorders (ICSD-3), simplified its definitions.  Part of this effort was to work in concert with definitions of insomnia also chronicled by the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), the main reference in the fields serving practitioners of mental illness healthcare.

These major changes to how medical professionals define and approach insomnia stresses the importance in recognizing that insomnia is usually related to some other medical disorder. While insomnia is neither strictly a dysfunction of sleep, nor is it solely a dysfunction of mental health.

Most importantly, this recognition shared by leaders in both sleep and mental health medicine has led to simplified approaches that should help to streamline diagnosis, treatments for insomnia, outcomes, and future research. 

Types of Insomnia

As a result of these major changes in defining insomnia, this sleep disorder now falls into 3 categories: 

Chronic Insomnia 

At least 3 months of problems with falling asleep, staying asleep, or being impaired by sleep loss define this form of insomnia. Trouble with sleep occurs at least 3 times weekly and other health concerns related to sleep deprivation may be present.  

Short-term Insomnia

Complaints or symptoms are not ongoing and the problem has existed for less than 3 months.

Insomnia Disorder

When neither of the other definitions adequately describes issues with sleeplessness.

A word about hyperarousal

Breaking it down even further, there are 2 distinct subgroups of people who can't fall asleep or who can't stay asleep, which are differentiated as a means for choosing appropriate treatment:

Those with physiological hyperarousal. People in a hyperalert state generally don't get enough sleep because of this condition of arousal.

Hyperarousal occurs when the sympathetic nervous system overreacts, leading to exaggerated startle responses, hypersensitivity to sensory details in the environment, and an inability to calm the mind.

These people are at higher risk for problems with hypertension, heart arrhythmias, type II diabetes, cognitive dysfunctions, and psychiatric problems.

Those without physiological hyperarousal. Without hyperarousal as a driving force for insomnia, these people are less likely to suffer from the same related effects of insomnia as their hyperalert companions.

Who is most at risk for having insomnia?

Insomnia is more common in women than in men. Older people are more likely to suffer from insomnia that children.

Not surprisingly, people who are experiencing major life stress (due to divorce, job loss, or retirement) often can't sleep at night. People with major depression and anxiety disorders are also at a much higher risk for experiencing signs of insomnia.

Smokers and people who use alcohol to fall asleep at night are also more likely to shorten the amount of sleep they actually get, night after night, because of those habits. 

What are the symptoms of Insomnia?

Nighttime insomnia symptoms include:

Daytime consequences of insomnia include:


What are the causes of insomnia? 

Here are the most common insomnia causes:

Medical conditions. These reasons for insomnia could arise from either physical or mental health problems.

Either the discomfort of the symptoms leads to sleeplessness (such as with GERD), or the medical condition itself interferes with the sleeping process. 

Menopause. Changes in hormones can stir up brain chemistry, leading to sleeplessness, often with wakeful periods around 3 a.m. Menstrual cycles may also be to blame for some cases of insomnia.

Prescription or over-the-counter drugs. Insomnia frequently occurs as the result of taking certain medications.

Alcohol, caffeine, marijuana, nicotine usage. All of these can interfere with healthy sleep architecture and lead to sleeplessness.

Undetected sleep disorder. Obstructive sleep apnea, restless leg syndrome, and circadian rhythm disorders may account for insomnia.

Poor sleep hygiene. The conditions of your sleeping environment and habits, which you can control, may make it harder to sleep well and lead to sleepless nights. 

Voluntary sleep restriction. Having an unusual sleep schedule due to work, social activities, or a family crisis can lead to bouts of insomnia. (How much sleep do you actually need to avoid accumulating sleep debt?)

Learned behaviors. Sometimes we pick up habits from childhood that are never resolved in adulthood, leading to troubles getting enough sleep.

Genetics. Insomnia patterns can run in families and be inherited. 

What are the risks of not treating insomnia?

Insomnia is highly prevalent and, if left untreated, dangerous to one's well being.

Insomnia has been linked to obesity, stroke, diabetes, hypertension, and heart disease. It may also be associated with untreated sleep disorders (such as obstructive sleep apnea).

Perhaps one of the most problematic behaviors that comes from not successfully treating insomnia is the abuse of drugs (legal or illicit) and/or alcohol in order to "self medicate" to achieve sleep. 

As you may have already guessed, identifying what causes insomnia for any individual may require a bit of detail gathering. However, insomnia typically doesn't require an overnight sleep study for diagnosis, unless there are other potential sleep disorders the physician needs to rule out.

See your doctor if patterns of sleeplessness are beginning to trouble you and leave you with undesirable daytime symptoms. A proactive approach guided by a knowledgeable physician is your best best for finding relief from insomnia.


Centers for Disease Control (CDC)
International Classification of Sleep Disorders, 3rd Ed.
National Sleep Foundation
Psychiatric Times
Review of Brazilian Neurology
Sleep Medicine
Sleep Medicine Review


You Might Also Enjoy...

Parasomnia: 5 Interesting Facts You Didn’t Know

If you walk, talk, eat, or even drive while you’re asleep, you’re experiencing a parasomnia. Here are five facts about parasomnia, along with advice on what to do if you engage in unusual behavior while you sleep.

How Sleep Problems Increase with Age

As you age, you may have more trouble falling asleep, staying asleep, and getting enough sleep to feel refreshed. It’s normal for age to affect sleep, but there are steps you can take to get the rest you need.

Can Melatonin Really Help You Sleep?

If you’re having trouble falling asleep or staying asleep, you may think of taking melatonin supplements. But do they really help with sleep? For some people, the answer is yes.