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The immune system is the body’s defense system that fights off foreign intruders like bacteria, viruses and parasites. Its cells also constantly patrol the body in the search for sick cells like e.g. cancer cells.

What is the immune system?

If the cells of the immune system find a sick cell, they stop the spread of the disease by killing the cell.

The immune system consists of many different types of cells, that can kill foreign intruders, and sick body cells, eat them, and produce are great variety of chemicals like antibodies and other effector molecules that can call for help, flag intruders for destruction or kill them directly. The cells of the immune system also produce messenger molecule to communicate with each other.

If the immune system encounters an intruder certain immune cells will retain the memory of this attack and will be able to respond faster and stronger, if, later in life, they encounter this same intruder again. This is what makes vaccinations possible which show a weakened version of the pathogen or parts of it to the immune system, so that it can react better if the real pathogen comes around.
The immune system is intricately connected to the hormonal system and the brain via messenger molecules, so that emotional stress and factors like insomnia have a great influence on its ability to function properly. Since the cells of the immune system have a very high turn-over rate, and most of the products of the immune system like antibodies and messenger molecules are made from protein, the nutritional and metabolic state of the organism also has a strong impact on the ability of the immune system to respond to an attack quickly and efficiently.

What is insomnia?

Insomnia is a sleep disorder. People with insomnia have either trouble falling asleep, staying asleep, or both. There are to main forms of insomnia: primary insomnia where people experience trouble sleeping without any underlying medical conditions that might cause them, and secondary insomnia, where the problems with sleeping are caused by another medical condition or a substance the person has been taking. Conditions that can cause secondary insomnia are e.g. pain, heartburn, asthma, depression, or ingesting caffeine and other stimulants close to bed time.

Insomnia can be acute, which means it last only a short amount of time, or chronic which means it lasts a long time. Insomnia can cause the patient to feel tired during the day, and it can make it hard to function. This can lead to secondary symptoms like a decreased performance at work or school, a lowered self-esteem, and depression. It can have a significant impact the quality of life and also can have serious health consequences.

Insomnia is one of the most common medical complaints and it is estimated that as many as a third of adults have insomnia at some time. Primary insomnia can be brought on by significant stress like the loss of a job, grief, or divorce.

What is stress?

Stress is the biologic response to a possibly (real or imagined) dangerous environmental stimulus. Stress can come in two different forms: acute (short-term) and chronic (long-term) and the two forms have a significantly different impact on the body. Short-term stress responses are an evolutionary ancient way to cope with dangerous situations and the body’s adaptations to it are also called the fight-or-flight-response. It includes the increased secretion of hormones like adrenalin that increase heart rate, blood pressure, and breathing, and the metabolism.

The fight-or-flight response can make us feel awake and in control. It can also make people aggressive. Studies on short term stress induced by activities like e.g. bungee-jumping have shown that it can increase the efficiency of the immune response and can make us less susceptible to infectious diseases. The acute stress response will reside after several minutes to a few hours, once the reason for the response is removed.

If the reason for the stress (the stressor) is not removed the body reacts with a different coping mechanism. It produces the chronic stress response. The chronic stress response is mainly characterized by the increased secretion of corticosteroids. These hormones can cause metabolic changes that can lead to weight gain, high blood pressure, insomnia, and other negative consequences of stress.

How does stress affect the immune system?

Corticosteroids have a direct influence on the immune system. They are strongly immuno-suppressant because the can inhibit the ability of the immune cells to produce antibodies, kill sick cells and communicate. Therefore, chronic stress increases the risk of getting an infection. They can also alter an ongoing response in a way that can increase susceptibility to allergies and asthma. The metabolic change that stress hormones cause can also influence the way the immune system response to a foreign intruder.

Read More: Can You Inherit Stress?

How does insomnia affect the immune system?

Sleep is a very important activity. While sleeping, we refill our metabolic and psychological reserves, process memories, heal injuries, and reorganize many metabolic processes. If one is not able to sleep enough due to a sleep disorder like insomnia or even if someone does not sleep enough voluntarily, e.g. because “there is just not enough time”, there will be consequences for the entire body.

Though both acute and chronic insomnia can be induced by chronic stress, it can also work the other way around. Chronic sleep deprivation, whether due to insomnia or voluntarily, can cause the body to become stressed and increase the amount of corticosteroids, it produces. This way chronic insomnia can indirectly depress the immune system via the actions of corticosteroids and cause an increased risk for infections.

However, there might also be direct influences on the immune system. Studies have shown that animals that sleep longer produce more disease fighting white blood cells. Many studies in humans show that people who sleep longer, have a lower risk of getting sick, even when the shorter sleepers don’t consider themselves suffering from stress or insomnia.