Inflammation From Stress. A New Theory Of The Onset Of Depression

2024 Author: Harry Day | [email protected]. Last modified: 2023-12-17 15:43

There are many theories for the development of depression. There are known theories about hormonal imbalance, about disruption of the synapse (change in the number of mediators). Currently, the most promising hypothesis is that mood disorders develop as a result of inflammation in the tissues of the brain.

Where does the inflammation come from?

There is a widespread belief that inflammation occurs only when foreign organisms enter the body: bacteria, viruses, fungi, etc. However, inflammation is a universal defense mechanism for which infectious objects are not required. Often, the immune system responds with an explosion of activity to external and internal non-infectious factors. For example, autoimmune diseases are widely known when the immune system attacks its own tissues. Hypoxia (oxygen deficiency in tissues) can also activate the body's defenses. Stress has a similar property.

Since the brain is a unique organ, its defense mechanisms are completely different from those in other parts of the human body. In addition to neurons, it contains auxiliary cells - neuroglia. The protective functions are assumed by one of the types of neuroglia - microglial cells. These are phagocytes capable of absorbing infectious objects and "digesting" them. In addition, they release a large amount of anti-inflammatory substances.

The anti-inflammatory substances released by microglia transform the environment in which the neurons are located and change their metabolism. As a result, the formation of mediators responsible for the transmission of impulses between brain cells is disrupted. The microglia itself also changes shape. Many processes appear, and cells migrate towards nearby synapses, probably affecting their function negatively.

Inflammatory Depression Theory

It has been shown that stress, especially chronic stress, is the very factor that most affects the activity of microglia. It has been suggested that persistent negative experiences cause changes in brain function, which can ultimately lead to depression.

Pro-inflammatory substances can also be carried into the brain with blood from other organs and tissues. If there are enough of them, then they are able in the same way to cause disruption of the functioning of neurons and the activation of microglia. For this reason, among patients with chronic inflammatory diseases, the percentage of depressive disorders is higher than among healthy people.

Is the theory of inflammation the only correct one? Naturally, it has its supporters and opponents. The main cons are:

1. People react differently to stress. Not everyone gets depression, despite the fact that the trauma can be quite severe. It is not entirely clear: whether some people can independently overcome the destructive effect of inflammation, or whether it actually does not play a role in the development of depression (or does not play a significant role). It is possible that the brain responds with inflammation to depression, rather than stress.
2. While depression and chronic inflammation often coexist, it is impossible to say 100% that one causes the other. Disorders may well coexist. And not every person with inflammatory diseases is doomed to depression.
3. Many people with chronic conditions take anti-inflammatory drugs on a regular basis. If the inflammation hypothesis were 100% correct, then this group would be completely protected from depression. But that doesn't happen.

If inflammation is to blame for depression, why are mood disorders treated with antidepressants? After all, they act on completely different mechanisms, enhancing the transmission of neurotransmitters in the synapse. It turned out that some of the antidepressants also have anti-inflammatory activity. In one study, regular intake of fluoxetine and citalopram significantly reduced inflammation in arthritis in mice. It is likely that the drugs are also able to reduce inflammation in brain tissue. In addition, antidepressants have been observed to reduce the intensity of chronic pain, even if it is clearly inflammatory rather than psychological in nature.

Inflammation triggers

Obviously, depression is made up of many factors. Much depends on individual genetic characteristics, on the state of health and psychological properties. However, inflammation is indeed often present in depressed patients. It is not entirely clear whether this is a cause or an effect, but the fact remains. Moreover, inflammation accompanies not only depression, but also other neurological and psychiatric disorders, such as schizophrenia, multiple sclerosis, Parkinson's disease and sleep disorders. Therefore, it makes sense to take care of the causes that can cause changes in the functioning of the immune system.

How can you protect yourself from inflammation? Current Psychiatry editor-in-chief Henry A. Nasrallah believes that the main thing is to avoid triggers, triggers of inflammation. From his point of view, it can prevent the development of depression or reduce the severity of symptoms. He identifies 10 risk factors for the development of inflammatory phenomena in the brain tissues.

1. Smoking. The smoker inhales hundreds of toxic substances that the body seeks to get rid of. As a result, immune cells are activated in all systems and organs. It is believed that it is the immune mechanism that triggers all the processes associated with the effects of smoking. Many people with depression smoke. This is due to the fact that nicotine slightly improves mood and relieves anxiety. However, given the inflammation situation, in the end, smoking deepens the problems in the brain even more.
2. Unhealthy diet. Foods included in the so-called "Western diet" contain substances that provoke inflammation. These foods include refined sugars and saturated fats. With such a diet, a person constantly maintains inflammatory processes, which leads not only to a depressive state, but also to a disease of other systems and organs.
3. Diseases of the oral cavity (caries, gingivitis and periodontitis). Dental problems are the source of many health problems. People with untreated caries are more likely to suffer from diseases of the gastrointestinal tract, are prone to developing pneumonia. Chronic purulent foci of the oral cavity constantly keep immune cells on alert. Near the "bad" teeth, there is a fight against pathogenic bacteria, and immune cells actively secrete pro-inflammatory substances, which the blood carries throughout the body.
4. Violation of sleep hygiene. Lack of sleep leads to activation of immune cells in the brain, which leads to the release of inflammatory products.
5. Vitamin D deficiency. Yes, the lack of this vitamin occurs not only in children, but also in adults. Vitamin D is important not only for bone tissue, but also for the functioning of the immune system. It is known that in conditions of its deficiency, human immunity reacts too "sharply" to everything. That is, other things being equal, much more inflammatory substances are emitted than normal. Obese people are more likely to suffer from vitamin D deficiency. Every extra 10% of body mass index corresponds to a 4% decrease in vitamin D concentration. It is believed that the reason for this phenomenon is the dissolution of vitamin D in adipose tissue.
6. Obesity. Obese people have an increased risk of depression by more than 50%. Obesity isn't just about being overweight. In addition to destroying vitamin D, adipose tissue is also a constant source of anti-inflammatory substances that negatively affect the functioning of the entire body, including the brain.
7. Violation of intestinal permeability. Inflammatory bowel disease, such as ulcerative colitis, has been recognized as one of the causes of depression. The inflamed intestine becomes permeable to certain substances that normally should not enter the bloodstream. The body responds with the release of anti-inflammatory substances, which causes depression.
8. Stress. As mentioned above, stressful events are the trigger for inflammatory reactions in tissues. This is true not only for the brain, but also for other body systems. For example, the same mechanisms are involved in the development of damage to the cardiovascular system.
9. Allergy. Also a kind of "inflammation". However, it is not microorganisms that act as foreign agents, but, as a rule, proteins of substances coming from outside. These can be food, pollen, medicinal substances, elements of the bacterial cell wall. The meaning of what is happening is the same - the immune mechanism is triggered, as a result of which substances responsible for the development of inflammation are formed in the body.
10. Sedentary lifestyle. In fact, a combination of several factors: usually obesity, vitamin D deficiency and an inappropriate diet.