Every human being has at some point in their life experienced at least one event that generates anxiety: an academic exam, a job interview, a sports competition, meeting an important person, or worry about a romantic relationship… these are some of the events that trigger feelings of apprehension. Generally, people’s anxiety is linked to future events. Halgin and Krauss (2009) define anxiety as “a state in which the individual is excessively apprehensive, tense, and worried about the possibility of something terrible happening” (p.162).
What is anxiety from a psycho-biological approach?
According to the DSM-V (2014), anxiety encompasses a series of clinical disorders ranging from separation anxiety disorder, selective mutism, specific phobia, social anxiety disorder (social phobia), panic disorder, agoraphobia, generalized anxiety disorder, substance/medication-induced anxiety disorders, anxiety disorder due to another medical condition, to specific or unspecified anxiety disorder.
The anxious response, which can sometimes be considered part of the survival instinct, becomes abnormal when its intensity level interferes with the subject’s daily and independent functioning. According to WHO/PAHO estimates for 2020, anxiety disorders had a prevalence of 4.3% in Latin America and the Caribbean. Therefore, scientific research that can yield significant results for the etiological understanding of this group of psychopathological disorders, for subsequent intervention, is of utmost importance.
For Clark et al (2020); The spinal cord, medulla oblongata, pons, midbrain, diencephalon, cerebellum, and cerebral hemispheres are the constituents of the central nervous system, remaining covered by the blood-brain barrier, which communicate with the entire body through the autonomic or peripheral nervous system. Likewise, information captured by the sense organs that travels from the peripheral nervous system to the central nervous system is called afferents, while efferents are the responses of the central nervous system that emerge towards different parts of the body through the peripheral nervous system.
According to Gadea et al (2018), afferents are linked to the sensations captured by the different sensory organs and that will be initially processed in the respective cerebral somatosensory areas. For its part, the admission of stimuli captured by the senses to the brain occurs with a previous station in the thalamus. The latter is a valuable structure housed in the diencephalon.
Herlyn (2015) states that “the expression of anxiety takes over the body, producing motor, automatic, and endocrine responses” (p. 2). Based on this, this author assures that anxiety is observable and includes unconscious responses; ensuring that the direct thalamic route is where information travels to the amygdaloid nuclear complex, which will generate the motor response. The amygdaloid nuclear complex is a subcortical part of the limbic system. The amygdala is responsible for coordinating responses linked to the expression of anxiety. This generates a motor response that can be fight, avoidance, or flight.
The response generated by the direct thalamic pathway is subcortical. This same author, Herlyn (2012), states that the motor response process, common in some types of anxiety such as generalized anxiety or panic attack, can be summarized as afference – thalamus – amygdaloid nuclear complex – efference; which corresponds to action without thought.
For its part, according to this theory, automatic expression depends on the brainstem nuclei. Afferents that generate pain arrive directly at the brainstem nuclei. They also receive afferents from the amygdala. The sympathetic response generates an increase in heart rate or tachycardia, perception of heartbeat, increased respiratory rate, blood pressure, and in general the activation of the pontine nuclei that are linked to states of alertness or wakefulness.
Furthermore, this same theory asserts that when the amygdala transfers stimuli to the hypothalamus, the hypothalamus-pituitary-adrenal axis is activated. The hypothalamus is the gland where CRH or corticotropin-releasing factor is released, which impacts the pituitary gland.
In conclusion, psycho-biology emphasizes the hypothalamus in relation to the anxious response process. Likewise, it considers the amygdala as a determinant in anxiety.
Similarly, there is the theory explained by Pacheco and Ventura (2019) which states that every anxiety disorder is activated by the response to stress, which is the organism’s manifestation to stimuli considered dangerous, activating the sympathetic system, releasing cortisol from the adrenal gland. These authors state that there are at least four neurotransmitter systems involved in distress, which are: serotoninergic, GABAergic, dopaminergic and noradrenergic. Finally, they state that a disturbed functioning of the hypothalamic-pituitary-adrenal axis has been linked to high levels of anxiety in children and adolescents, as well as separation anxiety symptoms being associated with high cortisol levels.
There is another theory that states that people with panic attacks have an excess of norepinephrine in the brain, which is a neurotransmitter that is activated when the individual is placed under stress or in a dangerous situation (Halgin and Krauss: 2019).
Another theory proposes that people with anxiety disorders suffer from a defect in gamma-aminobutyric acid (GABA), which has inhibitory effects on neurons. In support of this theory, evidence has been found of a decrease in the response of GABA receptors in the cortex of individuals with panic attacks. In this sense, distress is the result of low activity of the GABA neurotransmitter system. Neurons in the subcortical parts of the brain become more active with less GABA than inhibited ones, in people with anxiety disorders. (Halgin and Krauss: 2019).
Another theory of utmost importance for those of us dedicated to the field of mental health is Lang’s (2008) three-dimensional theory, which suggests that anxiety manifests according to a triple response system: cognitive, behavioral, and physiological. This last response is related to an increase in the activity of two main systems, the autonomic and somatic nervous systems, but also as part of the activation of the neuroendocrine activity of the central nervous system.
Reviewing the neurobiological theoretical background of anxiety allows the clinical psychologist to understand the importance of collaborative work between the psychologist and different medical specialists, especially with the psychiatrist and neurologist. All this with the intention of improving the problematic situation of the patient who consults and their family group.