Biology of Fear and Anxiety

What Is the Biology of Fear and Anxiety?

Fear is a primitive human emotion that is caused by specific threat-related stimuli leading to adaptive behaviors aimed at preventing or coping with that threat. The central organ that controls and regulates fear is the amygdala, an almond chapped structure located deep within the brain’s temporal lobes.

What Is the Function of the Amygdala in Fear?

The amygdala is the central hub for the management of fear within a network that involves other brain organs including the thalamus, the neocortex, the hypothalamus, the pituitary gland, the hippocampus, and the adrenal glands located on the top of the kidneys.

When stimuli (e.g., environmental changes) are received by the thalamus, they are sent to the amygdala for processing which involves interrogating the memory siege, the hippocampus, for previous similar stimuli.

Once the information is received from the hippocampus indicating a potential threat, the amygdala triggers the hypothalamus-pituitary-adrenal axis to initiate an adaptative reaction [1].

What Is the Role of the Hypothalamus-Pituitary-Adrenal Axis in Fear?

In this event, the hypothalamus secretes CRH (corticotropin-releasing hormone) to stimulate the secretion of ACTH (Adrenocorticotropic hormone) by the pituitary gland leading to the secretion of cortisol by the adrenal glands as part of the “Fight-or-Flight” mechanism [2].

How Fear Is Biologically Controlled?

When stimuli (e.g., environmental changes) are received by the thalamus, parts of the stimuli are also sent to the neocortex, a brain structure responsible for thinking and rationality, which processes this information and informs the amygdala of the absence of threat.

What Causes Fear?

To better understand the fear and cope with it, it is essential to understand its causes. They are several theories that suggest the origin of fear such as individuals’ personality, social construction, anxiety sensitivity, modularity of the mind, basic emotion, and evolutionary [1].

1- What Is the Link Between Personality and Fear?

A study that analyzed more than 4892 studies on the relationship between anxious personality traits and fear, found that individuals who score high on anxious personality tend to generalize fear to safe or novel situations [3]. 

2- What Is the Link Between Social Construction and Fear?

Fear can be socially constructed through mass media, horror movies, and news. For instance, as media is an integral daily part of our lives, they can lead to the production and constitution of emotions and feelings, including fear, which can be socially shared due to the media-wide social outreach [4].

3- What is the Link Between Anxiety Sensitivity and Fear?

Anxiety sensitivity (AS) describes individual differences in cognitive and affective risk factors of fear of bodily sensations such as pain, pleasure, headaches, nausea, itches, and tickles.

A study investigated the effects of an anxiety-based smoking cessation treatment on 579 adults and found that 35.6% had at least one emotional distress disorder diagnosis, and 11.9% of individuals had at least two emotional distress disorder diagnoses [5].

4- What Is the Link Between Modularity of the Mind and Fear?

According to the theory of modularity of the mind, the mind is comprised of innate neural structures or mental modules. It was suggested that a module of fear also exists and controls threat-related stimuli through some specialized neural structures [6].

5- What Is Basic Emotional Fear?

This theory states that fear is an emotion that evolved from adaptations to fundamental life tasks through signal, physiology, and previous events. Using neuroimaging techniques, a study showed that basic emotions such as fear, happiness, anger, sadness, and disgust, have specific regional brain activations [7].

6-What Is Evolutionary Fear?

This theory suggests that fear is evolutionary and is associated with survival circuits that are found in all animal species. Due to the presence of sensory receptors and motor effectors within the central nervous system, that coordinates the interface between bodily functions and the environment, these survival capacities increased in complexity during evolution [8].

How is Fear Measured?

There are two types of tests used to measure the fear index: behavioral and psychophysiological measures [1].

1- What Are the Behavioral Measures for Fear Index?

Behavioral measures assess the correlation between self-report questionnaires and behavioral response:

 Skin-conductance response 

– Pupillometry

– Facial electromyography

– Potentiation of auditory startle

– Heart rate and respiration

– Salivary cortisol

2- What Are the Psychophysiological Measures for Fear Index?

Psychophysiological Measures are used to evaluate attention and emotion responses to stimuli:

– State-Trait Anxiety Inventory

– Beck Anxiety Inventory

– Anxiety Sensitivity Index

– Fear Survey Schedule

– Fear Questionnaire

– Social Avoidance/Distress Scale

– Albany Panic and Phobia Q

– PANAS-X Fear

– Fear of Negative Evaluation Scale

How to Deal with Fear?

Fear can lead to stress, anxiety, and panic attacks and several measures could be used to overcome fear such as taking some time off, facing our own fears, and learning about our fears to better face them; however, there are some debilitating fear conditions where therapy is required. In this case, therapies such as medications, psychotherapy, and hypnosis are used to treat specific phobias [9].


Several theories are suggested to explain the origin of fear; however, fear is likely originated from a combination of all those theories as most of them appear to overlap in some respects. One of the points that rises attention is the social construct theory where large media outlets can create a large-scale state of fear within a population, a country, or globally, that can lead to unforeseen consequences.


[1] Adolphs, R., 2013. The biology of fear. Current biology23(2), pp.R79-R93.

[2] Miller, W.L., 2018. The hypothalamic-pituitary-adrenal axis: a brief history. Hormone research in paediatrics89(4), pp.212-223.

[3] Sep, M.S., Steenmeijer, A. and Kennis, M., 2019. The relation between anxious personality traits and fear generalization in healthy subjects: a systematic review and meta-analysis. Neuroscience & Biobehavioral Reviews107, pp.320-328.

[4] Renda, C.D., 2019. Watching” Insidious”–On the Social Construction of Fear. The Qualitative Report24(7), pp.1784-1804.

[5] Allan, N.P., Norr, A.M., Capron, D.W., Raines, A.M., Zvolensky, M.J. and Schmidt, N.B., 2015. Specific associations between anxiety sensitivity dimensions and fear and distress dimensions of emotional distress disorders. Journal of psychopathology and behavioral assessment37(1), pp.67-78.

[6] Gross, C.T. and Canteras, N.S., 2012. The many paths to fear. Nature Reviews Neuroscience13(9), pp.651-658.

[7] Vytal, K. and Hamann, S., 2010. Neuroimaging support for discrete neural correlates of basic emotions: a voxel-based meta-analysis. Journal of cognitive neuroscience22(12), pp.2864-2885.

[8] LeDoux, J., 2012. Rethinking the emotional brain. Neuron73(4), pp.653-676.

[9] Antony, M.M., Craske, M.G. and Barlow, D.H., 2006. Mastering your fears and phobias. Oxford University Press.

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