The word sensitivity is thrown around a lot in relation to a number of different things. It can refer both to the senses – that is, our ability to perceive the world around us – or to our tendency to be affected by the slightest action or attack from the outside world.
More than “sensitive”, some are labelled “hypersensitive”. People who fit this description are particularly emotive and readily shed a tear when watching romantic films or listening to sad songs, for instance.
The term hypersensitivity has become gradually more popular in recent years and is often applied, partly erroneously, to hyperaesthesia (a condition similar to sensory overload) or abnormally frequent intense emotions. With a view to avoiding these negative connotations of excess, we have opted to use the term heightened sensitivity in this article.
Sensitivity can occur either internally, in a physiological reaction or an emotion, or externally, in a movement of withdrawal, for example. In both cases, it is linked to internal (e.g., thoughts) or external (e.g., surroundings) triggers known as stimuli.
Taking on a variety of natures, stimuli can be social (e.g., a phone call from a friend, a colleague speaking to us or a stranger stopping us in the street), emotional (e.g., a memory of a loved one or a cuddle from a pet), physiological (e.g., a rumbling stomach or a racing heartbeat) or sensory (e.g., auditory, olfactory or visual).
Regardless of their form, we are continually exposed to them in our everyday lives. Relying on the resources in their environment to survive, humans are required to perceive, assimilate, and process all these stimuli to keep adapting.
However, not all of us react in the same way to each given stimulus…
Why do we have different levels of sensitivity?
Most people react in roughly the same way when presented with the same stimulus, while those who exhibit a stronger reaction are said to be more sensitive. This difference is explored in a number of theories, which were consolidated in 2016 under the umbrella term of environmental sensitivity.
This definition takes in the concept of sensory processing sensitivity (SPS, as measured by the highly sensitive self-test), which corresponds most closely in theory to what we refer to as “hypersensitivity” or “high sensitivity” in everyday language. Coined in 1997 by Elaine and Arthur Aron, it presents sensitivity as a personality trait bearing the following characteristics:
greater depth of information processing
heightened emotional reactivity and empathy
increased awareness of subtle changes in one’s environment
greater propensity for overstimulation
The concept of environmental sensitivity can also be seen as a metatrait, i.e., a higher-order personality trait that encompasses and justifies, to a certain extent, existing psychological concepts such as introversion, shyness, behavioural inhibition, or a reactive temperament.
This presents important implications for therapy, clinical diagnosis of mental pathologies, and research into the origins of certain mental disorders.
The negative effects often associated with heightened sensitivity
Historically, research on environmental sensitivity has focused mainly on determining individual vulnerabilities, which stem from many different factors (be them genetic, psychological, or physiological), and result in higher sensitivity to various stimuli.
In other words, our own inherent characteristics influence the way we are affected by our surroundings. For example, if an individual has a certain version of a gene associated with a lower production of the serotonin transporter molecule (a.k.a. the “feel-good hormone”), they are more likely to exhibit symptoms of depression during stressful events. As such, a genetic factor can produce adverse effects when combined with negative stimuli.
Nevertheless, these studies do present a certain bias. Given that a large proportion of the research links vulnerabilities to heightened sensitivity, the vast majority of studies associate negative environments (e.g., childhood abuse, insensitive parents or negative life events) with heightened sensitivity and its detrimental effects (e.g., predisposition to mental health problems or a poor quality of life).
As a result, heightened sensitivity is often associated with a form of vulnerability that offers very little benefit to daily life and encourages the emergence of complications in negative contexts, including social phobia, avoidant personality disorder, anxiety and depression, self-perceived stress, agoraphobia, alexithymia and autism spectrum disorder, and poor emotional regulation.
But are those with heightened sensitivity really predisposed to developing these adverse effects?
An adaptive advantage
A study on the heritability of sensitivity revealed that 47% of individual variations in sensitivity are genetically determined, while the remaining 53% are due to environmental influences. This means that sensitivity is a heritable trait. If heritable, it must therefore present some adaptive advantage (or at least, not be debilitating), however minor, to have been kept by natural selection down through the ages.
This trait may even have been long preserved through evolution, since it is also present in other mammals (as shown, for instance, by the reliable measurement of sensitivity in dogs published in 2017).
Moreover, numerical simulations and empirical research suggest that heightened sensitivity could be advantageous if present in 15 to 20% of the population as a negatively frequency-dependent trait. This means that individuals within a group can rely on their variations in sensitivity to employ diverse strategies, adapt more quickly to changes in their environment, and be more attentive.
Exploring potential benefits
For over a decade, an increasing amount of research has examined how beneficial environments can positively affect individuals with heightened sensitivity.
A 2015 study on the link between heightened sensitivity and responsiveness to a depression-prevention programme among teenagers showed that sensitive individuals were more responsive to the offered support. More importantly, such changes were considerably more noticeable in the highly sensitive subjects.
In 2018, another study revealed a link between heightened sensitivity and responsiveness to a school-based anti-bullying programme. In this case, not only was there a significant drop in bullying, but the phenomenon could be observed almost exclusively among highly sensitive individuals.
These studies suggest, therefore, that highly sensitive individuals have a better capacity for socialisation, reflective thinking, learning, and awareness.
These results are consistent with a brain imaging study that shows how, when exposed to positive or negative emotional stimuli, highly sensitive individuals experience increased activity in the areas of the brain linked to these same capacities (i.e., the hippocampus, parietal-frontal area, prefrontal cortex, etc.).
For example, showing them positive images (if they had a positive childhood) triggers increased activity in the centres associated with calmness, relating to others (i.e., the insular cortex) and reward responses (i.e., the ventral tegmental area, locus niger, and caudate nucleus). The latter of these acts as our basic survival motivator and can be involved in generating pleasure, including through substance use.
Similarly, presenting them with negative images causes overactivity in the areas associated with self-control (i.e., the medial prefrontal cortex), and cognitive and emotional self-regulation.
Making the most of hypersensitivity
Research into addiction and mood disorders has shown that the medial prefrontal cortex plays an important role in self-control, and that greater impulse control in response to positive stimuli is linked to reduced risk-taking and addictive behaviours.
This research suggests that heightened sensitivity, coupled with a healthy developmental environment, could be a factor in preventing addiction. This is because highly sensitive individuals may be less likely to exhibit abusive or problematic behaviours (related to Internet use, online gaming or gambling, etc.) or to become dependent after using narcotics.
All of these studies agree on the vital importance of a healthy childhood and environment. Given that environmental factors account for around half of all individual variations in sensitivity, it is essential to limit any negative experiences (or mitigate deleterious effects) that can be exacerbated by a sensitive personality trait.
Properly identifying individual sensitivity levels could prove helpful in gauging the success of certain therapies and intervention programmes. In fact, the importance of this particular success factor is such that therapygenetics research is currently moving toward more personalised psychotherapy.
How to thrive through hypersensitivity
Studies on environmental sensitivity are already starting to understand individual developmental differences under specific contexts and the related susceptibility to certain psychopathologies. This research may also be useful in early intervention for preventing abnormal developments in highly sensitive individuals, while giving them the tools to thrive in our modern society, with its many challenging stimuli.
In time, these studies will help shed light on this trait, in terms of the neural mechanisms involved, as well as its origin or associations with certain disorders.
Heightened sensitivity or hypersensitivity can therefore be a precious asset! Far from a mental disorder, it plays a vital role in the way we adapt to our environment. Its myriad evolutionary, medical and social implications are already being outlined in many ongoing studies in psychology, genetic biology and neuroscience. It is our hope that such research will allow the individuals concerned to overcome the prejudices that are all too often attributed to them.
Translated from the French by Enda Boorman for Fast ForWord.