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.

1. 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].

2. 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].

3. 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.

4. What Causes Fear?

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

A. 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]. 

B. 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].

C. 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].

D. 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].

E. What Is Basic Emotional Fear?

This theory states that fear is an emotion that evolved from adaptations to fundamental life tasks through signals, 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].

F. 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].

5. How is Fear Measured?

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

A. What Are the Behavioral Measures for the Fear Index?

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

  •  Skin-conductance response 
  • – Pupillometry
  • – Facial electromyography
  • – Potentiation of auditory startle
  • – Heart rate and respiration
  • – Salivary cortisol

B. What Are the Psychophysiological Measures for the Fear Index?

Psychophysiological Measures are used to evaluate attention and emotional 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

6. 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 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].

7. Frequently Asked Questions about What Is the Biology of Fear and Anxiety?

What is fear and anxiety from a biological perspective?

Fear and anxiety are natural responses to perceived threats or dangers. Biologically, they involve complex interactions between various brain regions, neurotransmitters, and hormones.

What brain regions are involved in processing fear and anxiety?

The amygdala, prefrontal cortex, and hippocampus are key brain regions involved in the processing and regulation of fear and anxiety.

The amygdala plays a central role in detecting threats and initiating fear responses, while the prefrontal cortex helps regulate and contextualize these responses. The hippocampus is involved in memory formation and emotional regulation.

What neurotransmitters are involved in fear and anxiety?

Neurotransmitters such as serotonin, dopamine, and gamma-aminobutyric acid (GABA) play crucial roles in modulating fear and anxiety. Imbalances in these neurotransmitter systems can contribute to the development of anxiety disorders.

How do hormones influence fear and anxiety?

Hormones like cortisol and adrenaline are released in response to stress and play important roles in the body’s fight-or-flight response.

Chronic stress and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which governs the release of these hormones, can contribute to the development of anxiety disorders.

Can genetics influence susceptibility to anxiety disorders?

Yes, genetics can predispose individuals to anxiety disorders. Certain genetic variations may impact the functioning of neurotransmitter systems or the regulation of stress response pathways, increasing vulnerability to anxiety.

How does the environment contribute to the development of anxiety disorders?

Environmental factors such as early-life experiences, trauma, chronic stress, and substance abuse can all contribute to the development of anxiety disorders. These factors can interact with genetic predispositions and alter brain function and chemistry in ways that promote anxiety.

Are there effective treatments for anxiety disorders targeting the biology of fear and anxiety?

Yes, several treatments target the biological underpinnings of anxiety disorders, including medication (e.g., selective serotonin reuptake inhibitors, benzodiazepines) that modulate neurotransmitter activity, and psychotherapy techniques (e.g., cognitive-behavioral therapy) that help individuals reframe their thoughts and behaviors related to fear and anxiety.

Additionally, lifestyle interventions such as exercise and mindfulness practices can help regulate stress response systems and alleviate symptoms of anxiety.


Several theories are suggested to explain the origin of fear; however, fear is likely to originate from a combination of all those theories as most of them appear to overlap in some respects.

One of the points that raises 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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