The 3 Most Important Biological Theories Of Anxiety
Anxiety has become a real epidemic in the 21st century. There are many people who suffer from this problem in their daily lives and, in many cases, at a pathological level.
We know how to define it, we have felt it, some of us suffer from it right now, but… Do we know where it comes from? Are we equally vulnerable to feeling it?
Of course, anxiety has a psychological part, which can be a great impediment to daily life, but it also has a biological part that is not at all omissible. Here we are going to see biological theories of anxiety and what mechanisms are involved
Since experiencing anxiety is a practically universal phenomenon, its definition is not difficult to understand. It is understood by anxiety the emotional response caused by being exposed to a problem or situation that may involve risk, whether on an emotional, physical or psychological level. Thus, the situations that generate it can be very varied and, depending on how the person experiences them, they will manifest a greater or lesser degree of anxiety.
But it is not only individual differences that are responsible for people manifesting varying degrees of anxiety. The consumption of certain substances also mediates this response, which demonstrates its biological basis.
It has been seen that certain medications such as decongestants and psychoactive substances such as caffeine imply an increase in this emotion Also medical diseases, such as acute myocardial infarction, make the patient more vulnerable to suffering an anxiety episode.
Predisposition towards anxiety disorders
As we were already saying, there is a different predisposition to suffer from anxiety and, consequently, to suffer from disorders associated with it. Research has tried to see to what extent biological factors may be involved in a person displaying excessively exaggerated behavior in the face of a stimulus that, perhaps, is not as dangerous as he or she perceives.
According to work carried out by Svenn Torgensen (1983), who evaluated the genetic risks of developing an anxiety disorder, hereditary factors seem to play a significant role. He saw that About 34% of monozygotic twins and 17% of dizygotic twins shared the diagnosis of an anxiety disorder
Components of anxiety
To understand anxiety a little better and relate it to the biological theories that try to explain it, it is necessary to review the three aspects involved in experiencing this type of emotion.
1. Cognitive
Anxiety arises before threatening anticipations or overly exaggerated assessments of potential risk of a certain stimulus.
Automatic thoughts that are negative may also be involved, triggering when the seemingly threatening situation appears.
2. Physiological
The autonomic nervous system is activated, implying changes at the level of circulation and respiration, which contributes to the perception of risk as something even more dangerous
3. Motor and behavior
The person can carry out various types of behavior when exposed to the threatening stimulus. Mainly, when faced with a dangerous element, one of the following two behaviors is carried out: either fight or flight
However, other behaviors are possible, such as submission to the individual who poses a threat or trying to de-escalate the environment. These behaviors are neither considered fighting nor fleeing, and are common in social animals.
These three aspects involved in the anxiety experience and response can involve very varied levels of intensity. However, when the intensity is very high and, in addition, There is no correlation between the anxiety-producing stimulus and the anxious response, we are talking about an anxiety disorder. In these cases, the degree of suffering is very high, in addition to entailing great incapacity for the person and damage on a physical, mental and emotional level.
How is the anxious response mediated?
The neurological mechanisms that produce and mediate the anxious response have been studied. The central nervous system, characterized by being a complex, dynamic and open system, is the structure involved in this process
Before going into detail about how the anxiety response occurs at an organic level, it is necessary to mention the structures that make up the central nervous system: spinal cord, medulla oblongata, pons, midbrain, diencephalon, cerebellum and both. brain hemispheres..
Signals from the outside are captured by the sense organs, which send signals to the peripheral nervous system and subsequently reach the central nervous system. Once they have been processed in the central system, it sends signals to the parts of the body to carry out an appropriate response.
Stimuli from outside are processed by different brain structures First, the stimulus passes through the primary association areas and then through the secondary ones, where they are combined with information from other stimuli. For example, visual information first passes through the occipital visual area, which is a primary area, but so that what is seen can be combined with what is being heard (for example, the song of a canary that we are seeing and hearing) it will pass to the secondary association area.
One of the structures involved in this process, whose importance is key in the manifestation of anxiety, is the thalamus. The thalamus is located in the diencephalon and has two main functions: it is a kind of relay station It stops information before it reaches the brain and also works as a filter for it. This way you avoid sending too much information to the brain, which could lead to real oversaturation.
Two pathways arise from the thalamus, responsible for responding to stimuli: the direct thalamic pathway and the indirect thalamic pathway. If the thalamus presents some type of dysfunction, such as not being able to prevent certain information from passing to the brain, psychopathology may occur. This has been seen in disorders such as schizophrenia and also in anxiety disorders.
Biological theories of anxiety
The anxious response involves up to three types of expression. On the one hand we have the motor, that is, the observable behavior that the individual can carry out when faced with the potentially harmful element, such as fleeing from it or facing it. Then we have the autonomic expression, such as the increased heartbeat and increased breathing, and, finally, the changes at the endocrine level, such as the secretion of certain hormones.
All the explanations that follow are biological theories of anxiety, which although they do not have a specific name, have tried to demonstrate how the body responds, at a neurological level, to a certain anxiety-producing stimulus, in addition to trying to explain the process. Let’s look at them further.
1. Motor expression
The direct thalamic pathway is, as its name suggests, the shortest and fastest The thalamus passes the information to the amygdaloid nuclear complex, in which the motor response will be orchestrated. The response in the direct thalamic pathway involves the following path: signal (afferent) – thalamus – amygdaloid nuclear complex – response (efferent). It involves action without thought.
For example, this circuit is the one that would be used if we put our hand on the lid of a pot that is burned and quickly removed our arm, without thinking about it. The amygdaloid nuclear complex is a subcortical structure, belonging to the limbic system. The amygdala has the role of coordinating responses linked to the expression of anxiety
As we already said, in most cases, the individual’s motor behavior when faced with an anxiety-producing stimulus can be either flight or fight, with some exceptions.
The indirect thalamic pathway is longer, involving the following structures: afferent – thalamus – prefrontal cortex – amygdaloid nuclear complex – efferent (motor response). This cortical response is more elaborate, more integrated and sophisticated The difference between the direct and indirect thalamic pathways is that the former is about 300 milliseconds faster than the latter.
When both pathways are not well coordinated, inappropriate and inefficient responses appear, such as being completely paralyzed by a dangerous stimulus. The functioning of the amygdala is controlled by the prefrontal cortex. Its most dorsal part is responsible for executive functions, while the ventral part is what inhibits the functioning of the amygdala when necessary.
2. Autonomous expression
Autonomic expression of anxiety depends on brainstem nuclei It is in this structure where the signals of those stimuli that imply some damage arrive, directly, such as being pricked with a needle or feeling a burn. They receive information from the amygdala, which, as we were already saying, is responsible for coordinating anxious responses.
When the sympathetic nervous system is activated, changes occur at the organic level, preparing the body for the dangerous situation. The body is in a state of alert, monitoring how the situation will evolve and preparing for the worst. Among these changes are an increase in heart rate or tachycardia, in addition to an accelerated respiratory rate. Blood pressure shoots up and pupils shoot up.
As opposed, The activation of the parasympathetic system involves responses that would not be adaptive in a threatening situation such as bradycardia, a decrease in heart rate, leading to cases in which the person suffers syncope or faints.
3. Endocrine expression
When the amygdala transmits stimuli to the hypothalamus, an important endocrine system is activated, the hypothalamic-pituitary-adrenal axis. The hypothalamus is a structure that is responsible for controlling the other glands in the body.
The hypothalamus releases a substance, adrenocorticotropic hormone-releasing hormone (CRH), which impacts the pituitary gland and both structures will impact the entire body through the release of adrenocorticotrophin (ACTH).
Among all the glands that The hormone ACTH will bathe the adrenal cortex, which produces corticosteroids Corticosteroids vary depending on the time of day. Normally, the maximum amount of this substance is secreted in the morning and they are related to the stress hormone cortisol.
When a stressful stimulus is presented, the hypothalamic-pituitary-adrenal axis is activated and the amount of cortisol in the blood increases. Cortisol implies changes at an organic level, such as greater performance, an increase in energy, a higher pain threshold, a decrease in the inflammatory response and promotes calorie reserve.
It also makes it happen an increase in carbohydrate intake, especially sugars It is for this reason that in stressful situations people tend to binge on sweet foods, such as ice cream, candy or chocolate.
When plasma concentrations of cortisol are high, the number of receptors for this substance in the hippocampus decreases. This causes a cognitive process such as episodic or biographical memory to be affected.
At the moment the anxiety stimulus disappears, cortisol is decreased, the number of receptors in the hippocampus recovers and episodic memory returns to a normal state. However, and in situations in which stress is too long, there is a suppression of cortisol production, something that has been seen in depression.
Cortisol in large quantities and in the long term produces a damaging effect on the neurons of the hippocampus It causes the number of dendrites to decrease, in addition to making them smaller.
But cortisol is not the only substance involved in the anxiety response. In anxiety states there is also an increase in the secretion of thyroxine, catecholamines, prolactin, vasopressin and growth hormone.
What do the experts say?
Once we have seen the biological bases of anxiety, the time has come to mention the main explanations that several scientists have tried to give to the phenomenon.
Michael S. Eison considers that a disturbance of the dynamic interactions between catecholaminergic and serotonergic neurotransmitters occurs in both anxiety and depression. In fact, he maintains that a manipulation of the serotonergic system affects noradrenergic tone. When there is an alteration in the balance of serotonergic neurotransmission, it contributes to the appearance of psychopathology, being anxiety when there is too much and depression when there is an absence
Jeffrey Allan Gray maintains that anxiety is generated from the stimulation of the behavioral inhibition system, which is located in the structures of the limbic system and connects with the brain stem and subcortical regions. This system can be stimulated by punishment cues or non-reward cues, and innate fear stimuli.
Joseph Ledoux gives importance to the direct thalamic pathway, which connects directly to the amygdala. This pathway is very involved in emotional reactions. According to Ledoux, emotional responses begin in this structure, even before being aware of the stimulus that causes us to react in an anxiety-ridden way or even without identifying it.
