Phobia - an extreme fear of specific external triggers - can manifest for a wide range of reasons. What does science have to say about the factors and the dynamics of prominent phobias, inducing acrophobia (fear of heights), agoraphobia (fear of crowded places) or aquaphobia (fear or water)?


Fear has been a fundamental part of the living world, predating humans.It is a universal sensation that plays a vital role in the survival of complex organisms.  Fear serves as our built-in defense mechanism, enabling us to protect ourselves from potential danger and learn how to navigate the world safely.

Phobia, in contrast, can be seen as fear gone awry. According to the DSM-5, the official guide for diagnosing mental disorders, published by the American Psychiatric Association, a phobia is a type of anxiety disorder. It is characterized by a state of irrational fear that could potentially be detrimental to the individual’s wellbeing. Among anxiety disorders, phobia is defined as excessive fear disproportionate to the actual threat posed by a specific situation, animal or object. Individuals with phobias often alter their behavior to avoid coming in contact with the source of their fear. Merely thinking about the phobia’s object can trigger anxiety. The more frequent and pervasive the cause of the anxiety, the greater its impact on an individual’s ability to lead a normal life, ultimately affecting their overall quality of life.

Phobias typically surface during childhood, but can develop at any age. The prevalence of phobias in women is twice as high when compared to men, which likely can be attributed to hormonal, chemical and cultural differences between genders. It is also possible though that men are less inclined to seek treatment, and thus remain underdiagnosed. Data from the American National Institute of Mental Health reveals that one in eight individuals in the United States will grapple with a  phobia at some point in their lives. These phobias can persist for several years and, in extreme cases, endure throughout a person’s lifetime. 

There are various types of anxiety disorders, and while they share some similarities,  in this article, the term "phobia" will only refer to the disorder that is clinically defined as "Specific Phobia". Other anxiety disorders, such as social anxiety (sometimes referred to as social phobia) and agoraphobia (fear of public places), have distinct characteristics and distinct clinical definitions despite sharing similar names.

Phobias can develop at any age, though they often emerge during childhood. A girl holding her face in fear |  Shutterstock, Parkin Srihawong


The Place Where Phobias Are Born

As of today it remains unknown why some people develop phobias while others do not. However, it seems that the development of phobias always involves a learning process that results in the phobia. For instance, a child who becomes lost at a birthday party, might develop a phobia of balloons (Globophobia).  Importantly, the connection between the object of the phobia and the traumatic experience doesn't have to be direct. The same phobia of balloons could develop following a loud and frightening event, such as a shooting or a terrorist attack. In this case, balloons might trigger fear due to their potential to suddenly burst and evoke painful memories. Sometimes, merely experiencing a traumatic event through television, reading an article, or a book, can be enough to cause a phobia.

  One of the more famous and groundbreaking studies in the field of phobias is the Little Albert experiment, conducted by behavioral scientists John Watson and Rosely Rayner of John Hopkins University in the United States. In their study, they had an infant named Albert, who was nearly one year old, peacefully play with a white rat. After a while they created a sudden, terrifying sound by striking a metal bar with a hammer behind him. Poor Albert started crying. After calming down, he resumed playing with the rat, but every time he touched the rat, the sound of the hammer strike appeared, which frightened Albert, causing him to cry. After several iterations of this cycle, the toddler refused to play with the white, furry rat. Furthermore, merely showing him the rat was enough to make Albert cry and try to get as far away from it as possible. 

In this manner the scientists demonstrated how something that poses no inherent threat can be associated with a distressing stimulus, causing an individual to become fearful of similar stimuli. When young Albert was presented with other small and furry animals, such as a bunny or a puppy, he exhibited fear, crying at the sight of them. This reaction indicated that he had begun to associate all small furry and white creatures with the fear experienced during the experiment. One of the conclusions of the study was also that Albert's fear response extended beyond animals - he showed signs of fear even when presented with objects like a fur coat or a Santa Claus mask.  

An ethically controversial experiment: Little Albert crying at the sight of a man in a Santa Claus mask | Credit: Akron psychology archives | John B Watson


This experiment, conducted nearly a century ago in the early 1920’s, remains ethically controversial. Current day scientists would never obtain approval to subject a child to such treatment, and for a good reason. The experiment serves as a poignant illustration of how classical conditioning works: a basic learning mechanism that forges associations between two stimuli, such that a reaction (fear) to one stimulus (a loud noise) is elicited in response to another initially neutral stimulus (the white rat), which did not cause such a reaction. However, unlike phobias, Albert’s fear conditioning did not endure for an extended period of time: to maintain his fear reaction to cute animals, the scientists had to repeatedly reinforce the conditioning of the fear response every few days. 

The experiment's significance in fear psychology research is overshadowed by criticism of its ethical aspects as well as of its methodological flaws.Among these criticisms are the facts that the experimental population consisted of only one subject without a control group.  Moreover, all of Albert’s emotional reactions were described verbally, lacking quantifiable data for statistical analysis. It’s also noted that Albert suffered from a neurological condition, which was the initial cause for his hospitalization during the experiment. Thus, no conclusions can be drawn from this experiment regarding the emotional reactions of healthy infants.


What Are We Afraid Of?

Not all phobias have been studied under laboratory conditions and pinpointing when and what triggers a specific phobia can be challenging. Furthermore, some scientists argue the tendency for certain phobias may have developed during evolution, providing a survival advantage to those who possessed them. For example, one of the more common phobias, the fear of snakes, can be seen as a logical response since avoiding interactions with snakes could save an individual from a deadly bite. The same rationale applies to many other common phobias, such as fear of heights or of small enclosed places. 

However, environmental factors seem to play a more significant role than evolutionary ones in phobia development. A survey of studies conducted on  twins has shown that the likelihood of two identical twins, who share identical genetic material, both suffering from the same phobia is statistically insignificant. 

Almost anything could be the object of a phobia, from thumbtacks to pillows and aliens. Naturally, we cannot discuss all of the possible types of phobias. Instead we will focus on a few common and particularly intriguing phobias and see what we can learn about them from current scientific literature.


Acrophobia: Fear of Heights

Acrophobia is an intense fear and anxiety response to high places or the mere thought of being in elevated locations. The basic fear of heights is a normal and common reaction, as falling from a great height can be extremely perilous. Most people experience some discomfort when looking down from a significant height, be it a tall cliff or the top of a skyscraper. What distinguishes those suffering from acrophobia is the severity of their fear, to the extent that it disrupts their daily lives. Some have trouble with tasks such as climbing up or down stairs, standing on a balcony or entering a multi-story building, even when the sturdy walls and railings efficiently prevent falls. The phobia can also manifest in response to more modest heights, such as ascending a few steps on a household ladder or standing on a stool. 

Studies that examined the development of visual depth perception in infants showed that even at a very tender age humans exhibit discomfort when presented with the illusion of height, such as standing or crawling on a transparent glass floor. When the infants crawled on such a clear surface, their heart rate noticeably increased. Acrophobia is in fact a relatively common phobia that impacts one in every twenty people. The response observed in these infants likely suggests a primal fear of heights that is inherent in all humans. However, the factors contributing to the intensification of this fear in some individuals while not in others continue to be a subject of ongoing investigation.

Acrophobia: an intense fear of heights, even if it is no life threatening | simona pilolla 2, shutterstock

In recent years, a growing body of research has challenged the notion that the fear of heights is solely acquired through learning. For instance, a longitudinal study conducted in Australia and New Zealand examined nearly a thousand children, starting from their early childhood and until they reached the age of 18. Surprisingly, the study found that children who had experienced substantial falls from high places did not show a significantly increased tendency to develop a phobia of heights. 

Another hypothesis suggests that acrophobia may originate from physical impairments that disrupt the equilibrium and stability of certain individuals, thereby compromising their sense of safety in high places. To investigate this, a study published in 2008 assessed 31 subjects suffering from acrophobia, using an extensive posturography examination. This examination assesses one's spatial orientation, which relies on a combination of equilibrium, visual cues, and sensory mechanisms located in the feet. The findings revealed that individuals with acrophobia tended to have impaired equilibrium compared to others and struggled to control their posture.

The same individuals also often experience difficulties with spatial orientation, ranging from discomfort triggered by motion, such as car-sickness, to a tendency for dizziness, shortness of breath and an elevated heart rate.Similar symptoms were also found in people who suffer from problems with their vestibular system, responsible for balance and orientation, such as vertigo, a phenomenon characterized by dizziness and loss of orientation. There is a lively ongoing debate regarding the potential link between vertigo and acrophobia.  

Other researchers have demonstrated that the quality of equilibrium and body control is a good predictor of the severity of the fear of heights in individuals. Based on the assumption that individuals who have struggled with posture control tend to rely primarily on their sight when in motion, a series of complex tests were conducted on a group of 45 subjects to explore the relationship between the fear of heights and the level of reliance on sight versus posture. The tasks that the subjects were asked to perform were designed to test this connection. For instance, one task involved positioning a stick within a distorted and warped frame,  requiring subjects to align it perpendicular to the ground. Those who relied more on their sight tended to place the stick at a slightly awkward angle, whereas those emphasizing posture were more precise. Another test challenged subjects to stand still for two minutes on a narrow line with one heel against the toes of the other foot, eyes closed, and hands crossed in front of them. Measurements of their body movements and the frequency of tripping helped to assess the quality of their posture and equilibrium. 


Another test, conducted at the top of a five-flight staircase aimed at assessing their anxiety levels at varying heights. Based on the hypothesis, subjects who were more reliant on their sight and had trouble maintaining their equilibrium and posture with their eyes closed, also experienced stronger fear in response to height. 

Such studies underscore the complex interplay between body and mind in phobias such as acrophobia. Currently, there is no definitive understanding of whether posture difficulties lead to phobias or vice versa. The more we learn about the links between these factors, the greater the odds that we will be able to help those affected by such disorders. 

Fear of Enclosed Spaces

Every eighth person in the world suffers from some degree of claustrophobia - fear of enclosed spaces, and this phobia as well is more common in women. This anxiety emerges when staying in narrow or enclosed spaces or when approaching them - like caves, tunnels, elevators, basements, airplanes and narrow medical imaging machines, like MRI machines. The fear can emerge even when the narrow space has accessible exits, such as windows or doors.  

 An MRI test can pose is a significant challenge for individuals suffering from claustrophobia | zlikovec, shutterstock

In the past it was widely believed that the propensity to develop, fear of enclosed spaces, primarily stems from traumatic childhood experiences. Some cases seem to support this explanation, such as the story of a 55 year old woman who struggled with a CT scan due to a phobia developed during childhood after being locked in a small bathroom stall for over ten minutes. However, in recent decades this perspective began to shift and expand, following the rise in cases of individuals who suffered from claustrophobia but were unable to point to a relevant childhood event as an origin for the phobia. So it appears that the mechanism of fear acquisition is not the sole explanation for claustrophobia.  

A 2020 study identified a neural pathway triggered in mice when placed in confined spaces, leading to claustrophobic behavior. When the same neural pathway was artificially stimulated outside of confined spaces it resulted in the mice demonstrating the same claustrophobic behavior patterns. Thus, it appears that at least in mice there is a clear physiological basis for phobias and their associated behaviors.

Current genetic studies further contribute to our understanding of the puzzle, indicating that sometimes hereditary factors can play a role in specific phobias. One such factor is a gene in charge of producing a protein that is active in the brain region responsible for emotional processing during stressful situations. Mutations in this gene have been previously linked with an increased tendency for recurring anxiety attacks in humans. 

In a 2013 study, researchers demonstrated that mutating this gene in mice led to claustrophobia-like behaviors, including restlessness, distress vocalizations and increased heart rates when placed in confined spaces. These mice displayed normal development and behavior in larger cages but exhibited signs of anxiety and distress when transferred to smaller cages. In contrast, regular (control) mice continued to act normally after being transferred to the smaller cage. From this the researchers concluded that the protein that the gene encodes for plays a crucial role in regulating emotional reactions to fear in mammals, and its impairment could result in uncontrolled emotional responses.

In humans, there also appears to be a link between this gene and fear reactions. When researchers compared the sequences of the gene in individuals with claustrophobia and those without, they found several differences that were more frequently observed in people with claustrophobia.  While it is possible that different gene variants of this gene contribute to this specific phobia, a definitive explanation for how this gene leads to such a common phobia in humans has yet to emerge.  Additionally, the gene version that was linked to claustrophobia was not identified in all the claustrophobic individuals, and there were also individuals who did not suffer from claustrophobia but were found to carry this specific version of the gene. Thus, it is clear that other factors are also involved in the development of this phobia.


The fear of entering caves or tunnels could have a genetic component | Shutterstock, Ginger Livingston Sanders


Aquaphobia: Fear of Water

In 2021 medical doctors from the United States published a report about a 69 year old man who complained about a persistent cough and shortness of breath, which began about a year after he began treatment for lung cancer. Alongside these symptoms, there was a dramatic change in his attitude towards water. Any water-related activity, even the mere sight of a glass of water, triggered panic, shortness of breath and suicidal thoughts. He went to great lengths to avoid any interaction with water, to the extent that he repeatedly suffered from dehydration. Since lung cancer often manifests with coughing and shortness of breath, his doctors suspected that he may have choked or coughed while drinking water, leading to the development of this phobia. After four months of treatment with anti-anxiety medication and breathing exercises, his condition improved,  allowing him to engage in activities involving water, such as drinking and showering, once again.

While avoiding high or narrow places  can impact one's quality of life, a phobia of water can pose a genuine threat to the lives of those who suffer from it. In severe cases, individuals with aquaphobia avoid brushing their teeth, forego showering, and even refuse to drink water, leading to dehydration, poor hygiene, and potential health risks.

For this reason severe phobia of water requires instant and effective treatment. You can assume that it will usually include exposure treatments, when the patient is guided through gradual exposure to the object of his or her phobia. An extreme case of this could be found in Steven Spielberg’s movie “Jaws”. The protagonist suffers from aquaphobia that developed following a drowning experience in his childhood; during the movie he overcomes the phobia and finally defeats a killer shark while his boat is sinking into the sea.  

In reality you do not need such an aggressive exposure treatment to overcome fear of water. You can start with a friendlier task - like looking at images and videos of water, or placing your hand under a running tap. Other treatments include anti anxiety psychiatric medicine and relaxation techniques such as breathing exercises and meditation.  

Exposure treatment helps patients to gradually learn to cope with their fear | ThirtyPlus, shutterstock

It's important not to confuse aquaphobia with the deadly medical condition known as hydrophobia. In both cases, there is a profound fear and aversion to water, but hydrophobia is not an acquired anxiety; instead, it is an advanced symptom of rabies that appears in 50-80 percent of rabies cases.

The rabies virus infects mammals, including dogs, jackals and humans. It damages the brainstem - a region in the central nervous system that is responsible for basic vital functions, such as consciousness, pulse regulation, breathing and swallowing. As a result of this damage, whenever a patient attempts to swallow,  their respiratory muscles contract forcefully, obstructing the throat and preventing swallowing. For the same reason many rabies patients drool and foam at the mouth - they are unable to swallow their own saliva. Additionally, patients develop an intense aversion to water, which is associated with their convulsions triggered by any sight or thought of water.

Rabies is a fatal and incurable disease, typically causing death within two weeks of infection. However, the existing vaccine against rabies is one hundred percent effective, provided that it is administered before the onset of symptoms. This underscores the importance of promptly reporting to health authorities any animal bites or exposure to the saliva of an animal of unknown rabies vaccination status and seeking immediate vaccination.


Living Without Fear?

Similar treatments to those that help people who suffer from aquaphobia, ranging from relaxation techniques to anti-anxiety medications, are also used for addressing other phobias. However, many individuals who suffer from phobias do not seek treatment, primarily out of fear, which hinders them from confronting their phobia’s triggers.  

As previously stated, one of the more common and effective methods for confronting phobias is exposure therapy.  In this approach, patients are gradually and systematically exposed to the source of their anxiety in a controlled manner. . This exposure allows them to become accustomed to the presence of the fear-inducing object or situation and teaches them how to manage the overwhelming fear. In recent years virtual reality goggles have been used to confront phobias, allowing individuals to face their fears without the actual physical presence of the feared object. Some studies have found that combining exposure therapy with relaxation techniques enhances the effectiveness of both treatments.  

Would Life Be Easier Without Fear?

An article published in 2011 discussed a woman who experienced a lack of fear, which demonstrated the potential dangers of living without fear. This woman had suffered damage to her amygdala, a brain region responsible for emotional reactions, leading to her inability to experience fear. Various attempts to frighten her, including exposing her to venomous snakes and spiders, taking her on a tour of a haunted house, and showing her horror movies, proved futile. Out of curiosity she even attempted to touch the snakes, which could have bitten her if not for the researchers’ intervention. This case indicates that living without fear can be dangerous. 

Many phobias have an evolutionary basis, as they promote avoidance of potential dangers. What remains unclear is what causes a reasonable and healthy fear to escalate into an anxiety that disrupts everyday life. The most effective way to overcome a phobia is by facing the fear gradually within a therapeutic framework, where individuals can learn to control their automatic emotional reactions. This approach has proven successful in about 90% of cases