— Recently, a group of scientists from the University of California at San Diego discovered a new mechanism responsible for the occurrence of acute fear. The researchers concluded that at times of stress, connections between neurons switch from the excitatory neurotransmitter glutamate to gamma-aminobutyric acid (GABA), which performs inhibitory functions. What does this data say?
“This is very logical, since the brain needs to limit the hyperarousal that occurs during times of stress. Naturally, the restriction of neuronal excitation occurs as a result of the secretion of an inhibitory neurotransmitter, in particular GABA. So there is nothing sensational in these data, just another confirmation of already known mechanisms.
GABA is a kind of opponent of glutamate, which plays an excitatory role. The exception is early childhood, when GABA can also act as an excitatory neurotransmitter.
— Please tell us about the biochemistry of fear and stress - what and how happens at the moment of fear in the human body? And how does this condition develop if the stressful situation drags on?
— It is impossible to put an equal sign between stress and fear, since stress factors do not always cause fear. Fear is an emotion that accompanies stress, but this is not always the case. In general, stress factors are divided into biotic and abiotic; their influence is not always accompanied by the emotion of fear. Biotic are associated with the impact on the body of other living organisms, abiotic - with unfavorable conditions and environmental factors, such as climate, temperature, intense physical activity, etc.
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If we talk directly about stress and how our body copes with it, then we should mention three main endocrine mechanisms: somatotropic, thyroid and adrenocortical. That is, during the development of the adaptation syndrome (stress reaction), the production of somatotropic hormone by the pituitary gland, as well as thyroid and adrenal hormones, is activated. The adrenal glands produce adrenaline, norepinephrine, glucocorticoids, in particular cortisol and mineralocorticoids. In response to stress, a whole cascade of changes is launched in the body.
With fear, the balance of serotonin and dopamine also changes.
— Do all these changes help the body mobilize in the face of danger?
— Of course, fear is our evolutionary acquisition, which ensures our survival.
— What exactly does this hormonal cocktail do to the body, what changes occur next?
“With fear, not only does the level of norepinephrine, adrenaline and cortisol increase, but a cascade of processes is launched, including a sharp increase in the level of dopamine, which most people know as the “pleasure hormone.” Dopamine in our body acts as a neurotransmitter - a carrier of information from neuron to neuron. Dopamine affects the functioning of neurons in the amygdala, or amygdala, a key structure of the limbic system of the brain, which is responsible for the emergence of emotions, including fear. If increased levels of dopamine secretion in the brain persist for a long time, the threshold for the sensitivity of amygdala neurons to dopamine decreases. As a result, the person experiences constant anxiety and worry.
The amygdala is a key link in these processes. It includes many nuclei that have connections with different parts of the brain. Thus, the deep nuclei of the amygdala are connected to the frontal lobes, to the prefrontal cortex, which is responsible for the conscious control of our behavior. Other nuclei are connected to the hypothalamus - the center of all autonomic manifestations of fear, such as increased sweating, etc. These reactions are ensured by the connection between neurons of the amygdala and the hypothalamus, which is also functionally part of the limbic system of the brain.
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— As you noted, dopamine is usually associated with something positive, with satisfaction from achievements, joy... Why is it able to be actively produced in response to stress?
— The influence of any factor is optimal only within certain limits. When going beyond the optimum, negative effects arise. When dopamine acts as a pleasure hormone, a key component of the reward system and control of flow, it is secreted normally. Excessive production of dopamine causes restlessness, anxiety, and affective reactions.
— Is it possible to determine whether a person is experiencing chronic or acute stress by analyzing the level of cortisol in the blood?
— In principle, it is possible, but each person has his own characteristics, which are determined genetically. Cortisol is constantly secreted in the body; during stress, its level simply increases. Each functional state is characterized by its own hormonal cocktail. For example, a state of euphoria is also a form of stress, so-called eustress. In this case, there is also a strong release of adrenaline, an increase in the secretion of “happiness hormones” - serotonin, dopamine, oxytocin, endorphins and enkephalins.
— It is known that chronic stress destroys health, allergies can occur against its background, and it is also associated with the appearance of oncology and other diseases. Even obesity has been linked to increased cortisol levels and stress. What is the mechanism of stress’s influence on the body, immune and other systems?
“Normally, stress ensures our adaptation to the environment; in small doses it is even beneficial. A person accustomed to ideal conditions simply cannot survive when he finds himself in an imperfect and unfair world. But if stress becomes chronic, then it really destroys the body, causing, in particular, stomach ulcers. Its risk increases due to the fact that stress hormones (glucocorticoids, in particular cortisol) increase the secretion of hydrochloric acid in the stomach. As for obesity, it is not a direct consequence of increased cortisol levels, but rather is generally associated with metabolic disorders that can begin under stress due to the hormonal changes that I talked about at the beginning. In addition, many people tend to “eat” stress. But again, whether a person in a state of stress gains weight or, on the contrary, loses weight, depends on individual characteristics - many, for example, lose weight due to negative experiences.
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The immune system can also be affected by stress. This is due to the fact that high levels of glucocorticoids lead to atrophy of the thymus gland, as well as to a reduction in the lymph glands. As a result, the production of antibodies, lymphocytes, and the intensity of phagocytosis decreases. This increases the risk of infectious diseases, cancer and other ailments. Usually those diseases manifest themselves to which a person initially has a tendency - “where it’s thin, that’s where it breaks.”
— What signs, besides frequent illnesses, may indicate chronic stress?
— Let me give you the example of professional burnout, which is also a manifestation of chronic stress. The main sign of professional burnout is
reduction of the emotional sphere. Interest in work, in those things that previously interested and pleased a person, is lost. Plus, affective reactions and hot temper towards colleagues and household members are added. This is caused by excessive activation of the amygdala and, accordingly, increased sensitivity to adrenaline, serotonin and dopamine.
— Which specialists should I contact in such a situation?
— You can see a psychologist, but in general it depends on the specific manifestations, because often stress also provokes hypertension, since glucocorticoids increase the sensitivity of vascular smooth muscles to adrenaline and norepinephrine. Water retention in the body is also often observed, and swelling can also indicate chronic stress. But these same manifestations can be symptoms of a specific disease, so each case needs to be examined separately.
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— How can you reduce the risk of chronic stress at the lifestyle level?
— It is important to find an optimal balance between work and rest, as well as to have some other activities besides your main job. A good HR service of a company should monitor staff for professional burnout. If signs of burnout appear, it is advisable to send such an employee on vacation, even outside the schedule.
— Modern residents of developed countries face little real danger. At the same time, they are in a global information flow, constantly consuming news about disasters and catastrophes that are happening to other people somewhere. What has a stronger stressful effect on a person: the presence of real threats or being in a negative information context? Is it appropriate to compare this?
— Of course, the abundance of negative information affects us and can cause organic stress reactions. We may not even experience fear on a conscious level; the brain still reads negativity as a potential threat. At a minimum, in such a situation, people’s mood may deteriorate, but alarming reactions may also arise. One theory for the emergence of psychosis is that the brain is literally flooded with information as a result of a disruption in the filtering mechanism. A huge amount of information, including contradictory and negative information, leads to psychotic disorganization. Therefore, you should try to dose the impact of the information flow on the brain.