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The Pathophysiology of Insomnia

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The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.

Insomnia is a sleep disorder that affects millions of Americans. The main symptom of insomnia is the inability to fall asleep or to stay asleep. This results in a feeling of dissatisfaction with the amount and quality of sleep. As a consequence his or her productivity both at home and at work may get compromised. This is why it is important to get a better understanding of the pathophysiology of insomnia.

What is pathophysiology?

Pathophysiology is a medical discipline.  It studies the functions and symptoms of diseased organs. Medical experts conduct this study in order to diagnose a disorder.  It allows them to come up with appropriate patient care. Pathophysiology is slightly different from pathology. Pathology involves the study of all aspects of a disease instead of concentrating on just organic function.

Pathophysiology of insomnia

Insomnia is a product of an interaction of several factors. These include biological, psychological, environmental, and physical factors. Chronic insomnia in particular seems to occur only on patients who have an underlying predisposition to insomnia. Normal individuals fall asleep or stay asleep with ease. Individuals who suffer from insomnia have the following:

  • Increased risk of anxiety and depression
  • Higher rates of arousal
  • Increased daytime sleep latency
  • Increased metabolic rates
  • Greater variation in their night-to-night sleep patterns
  • Increased electroencephalographic (EEG) beta activity during sleep onset
  • Increased global glucose consumption while transitioning between waking and sleep onset.


Clinical research shows that individuals affected by chronic insomnia manifests increased brain arousal. Increased fast-frequency activity during non-rapid eye movement (NREM) sleep is common in patients with chronic insomnia. This is an EEG sign of hyperarousal. It is also evidence of reduced deactivation in vital sleep/wake regions during NREM sleep compared with controls.

Insomnia also causes higher day and night body temperatures. Those with insomnia also have higher urinary cortisol and adrenaline secretion. They also have higher adrenocorticotropic hormone (ACTH) compared to individuals with normal sleep. These results seem to be proof that insomnia is a manifestation of hyperarousal.

Mechanisms for stress

Stress is the response of a person to any change the requires an adjustment or response. The human body responds to these changes through mental, emotional, and physical responses. Stress is a normal part of a human’s life. An individual may experience stress from his environment, his thoughts, and his own body.

Stress activates the sympathetic nervous system. It also typically activates the hypothalamic-pituitary-adrenal (HPA). There is an indication of increased activities of the HPA axis in individuals with insomnia. This makes them reactive to stressors. When activated by the infusion of corticotropin-releasing hormone, the HPA axis produces sleep disruption in individuals without insomnia. Corticotropin-releasing hormones can also cause a decrease in nocturnal melatonin levels in normal individuals.

Individuals with insomnia have an increased metabolic rate, body temperature, and heart rate. In addition they have higher levels of cortisol and catecholamines. These suggest an increase in the activities of the body’s stress-response system. EEG showed higher levels of fast activity and lower levels of slow-wave activity.


There is evidence that suggests that sleep is not under the control of  just a single gene or a subset of genes. Instead control of sleep is the domain of a number of individual genes. It was also found that the neurotransmitters and signaling pathways that serve wakefulness serve other functions as well.

One study found that a person’s sensitivity to caffeine’s effect on sleep is a result of differences in the adenosine 2A receptor. This means that consuming coffee, tea, or any caffeinated beverages increases beta activity during sleep. When a person without insomnia begins to fall asleep the EEG should begin to slow. This does not occur in persons with insomnia.

Melatonin Levels and Insomnia

Patients with chronic insomnia have lower nocturnal levels of melatonin. Melatonin is a hormone that is responsible for regulating the Circadian Rhythm. An increase in melatonin levels in the body induces sleep. When an individual has insomnia they have lower levels of melatonin. The levels of melatonin show greater decline the longer a person has insomnia.

There is a study of the polysomnographic sleep patterns and melatonin secretion in children with chronic insomnia. This study used children who have healthy sleep patterns as well. Researchers noted their nocturnal plasma melatonin concentrations and measured on an hourly basis.  Aside from getting measured they were also statistically compared between those with insomnia and healthy subjects.

This study showed that plasma melatonin levels in children with insomnia begin increasing in the early evening. These levels were significantly lower during the middle of the night compared to the levels obtained from the healthy subjects. Severely reduced levels of nocturnal plasma melatonin showed up in test subjects with sleep disturbance longer than five years. The results of this study showed that the Circadian Rhythm of melatonin secretion is not normal in patients who suffer from chronic primary insomnia. It also showed that nocturnal melatonin secretion is significantly lower to patients who  

Understanding a disorder and what it does to the human body is of vital importance. The more we know how organs act in relation to a disease the better equipped we are of knowing how to come up with an efficient diagnosis. Pathophysiology also allows doctors and sleep specialists to come up with appropriate treatment plans not just for insomnia but for other sleep disorders as well. The knowledge gained from pathophysiology also allows doctors to minimize whatever side effects treatment or medication may have. This way sleep specialists can treat sleep disorders like insomnia with as little undesirable effects as possible.

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The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.

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