Insomnia

How often would you say you struggle to stay or fall asleep? If it's more than three times per week (and has been going on for at least one month), then you might have one of the most common sleep disorders: insomnia.

Insomnia is often used to refer to any sort of difficulty sleeping, though official clinical diagnoses exist. Some of the diagnostic criteria include nonrestful sleep, daytime difficulties stemming from a lack of sleep, and difficulty sleeping despite opportunities to do so. (See US clinical diagnostic criteria).

Causes

Insomnia can be caused by a wide array of behaviors, events, and circumstances, such as dealing with the death of a loved one, napping too close to bedtime, or taking certain medications.

Many cases of insomnia are secondary, meaning the insomnia itself is a symptom of another condition, such as anxiety or sleep apnea. Nearly half of all people with chronic insomnia have a comorbid psychiatric condition.

The neurobiology of insomnia isn't fully understood, and several theories seek to explain the phenomenon, which appears to be at least partially influenced by genetics.

One proposes that insomnia may be a disorder of hypervigilance or hyperarousal experienced throughout the day—this sort of state occurs when a person attempts to be constantly aware of any threats, leaving them tense, anxious, and easily startled. Another suggests the disorder stems from an issue with the sleep-wake cycle controlled by one's circadian rhythm.

Risks for developing insomnia include gender and age (women and older adults have a higher chance of developing the disorder), working night or rotating shifts, and having comorbid medical or mental health disorders, including PTSD, anxiety, and depression.

Health Impacts

Acute, short-term sleep loss can trigger higher activity levels of dopamine, a hormone and neurotransmitter related to reward, memory, and motivation. A 2023 study found a sleepless night led mice to be less depressed and more aggressive than the rested control group.

But two nights without any sleep? People's decision-making abilities begin to suffer, leading to blunted reactions and failures to adapt to changing circumstances.

Sleeping less than seven hours per night is associated with increased pain perception and higher risks of diabetes, heart disease, depression, and death.

Sleeping less than six hours increases heart rate and decreases activity in the parasympathetic nervous system, which controls the body's ability to relax.

This "tired-but-wired" state can further impede a good night's sleep, beginning a deleterious cycle of sleep loss and harmful health effects.

Human behavior and cognitive performance are nearly drunken after four nights of five or less hours of sleep—common during parenthood, college, and professional training.

The brain might try to overcome the sleep gap by briefly offloading different regions, a phenomenon known as "local sleep" that may explain at least some of the cognitive issues that crop up when humans get sleepy.

Research shows that sleep deprivation also contributes to the gathering of misfolded proteins in and around neurons (such collections of misfolded proteins are believed to contribute to Alzheimer's).

Treatment

There's no one-size-fits-all cure for insomnia, though interventions typically begin by improving sleep hygiene, encouraging people to adjust their sleep habits and presleep behaviors to better prioritize rest and relaxation.

Other common treatments include cognitive behavioral therapy and medication.

Some insomniacs find sleep by giving into the age-old bi- or polyphasic approach. This segmented approach to sleep is used across the animal kingdom and may have been humanity's go-to choice before the Industrial Revolution (and regular access to electric lights).