Highly Sensitive People: Genes, Brain Function, and Sensory Sensitivity

Key takeaways:
~ Approximately 15-20% of the population has characteristics that psychologists classify as Highly Sensitive People (HSPs).
~ HSPs are more sensitive to visual and auditory stimuli, more easily excited, and more attuned to the emotions of those around them.
~ Genetic research shows that variants in the dopamine pathway, stress-related pathways, and pain sensitivity pathways are common in HSPs.

What is a Highly Sensitive Person (HSP)?

Highly Sensitive People (HSPs) are individuals with heightened sensitivity to environmental stimuli, deeper cognitive processing, and high emotional reactivity. The term was popularized by psychiatrist Dr. Elaine Aron, who began studying and writing about the characteristics of HSPs in the 1990s.[ref]

In short, some people are simply more sensitive to both emotions and physical stimuli – such as small sounds, visual distractions, or the feelings of others around them. HSP is increasingly understood in the context of genetic variants, the combination of genetics and childhood experiences, and changes that can be seen on brain imaging scans.

Highly Sensitive Person Traits

Dr. Aron created a psychological test and scale to measure sensitivity. Based on this Highly Sensitive Person Scale, researchers narrow down the three factors that influence sensitivity:[ref]

• Easier excitation (HSPs tend to avoid scary movies and overwhelming situations)
• Aesthetically sensitive (HSPs notice colors, surroundings, artwork, and music)
• Low sensory threshold (They may be irritated by tapping pencils, the high-pitched hum of a fan, and bright lights)

These traits are found in 15-20% of the population, and psychologists have linked the trait to inheriting variants in certain groups of genes.

The terms “highly sensitive person,” “environmental sensitivity,” or “sensory processing sensitivity” are used in psychological research. While there are some technical differences in the definitions of these terms, in essence, researchers are able to quantify and describe the differences found in people who are highly sensitive to both negative and positive environments. These differences may include a heightened awareness of interactions with other people or a heightened sensitivity to the physical environment.

Some of the earliest research on this topic was done by psychologists, Dr. Elaine Aron and Dr. Arthur Aron, in the 1990s. Dr. Aron offers a free quiz if you want to find out if you are a highly sensitive person.

Another site for HSP quizzes and more information is sensitivityresearch.com. Note that when you do the quiz you have the option to enter your email or allow your answers to be used for research, but there is also a button at the bottom just to see your results without including your personal information.

Before we get into the genetics research, here’s a quick overview of the characteristics of an HSP:

1. Deeper processing: They often think deeply about things, reflecting more than average.
2. Emotional intensity: HSPs experience emotions more intensely.
3. Overstimulation by inputs: They tend to get easily overwhelmed by sensory inputs.
4. Sensitivity to subtleties: They are often more aware of slight changes in their environment.

Researchers have found that people tend to fall into three classes – high, medium, and low sensitivity.[ref]

Sensory Processing Sensitivity (SPS): Scoring High on the HSP Scale

Sensory Processing Sensitivity (SPS) is a psychological trait defined by psychologists as a heightened response to stimuli that most people find normal. People with SPS are more easily aroused and excitable, and they tend to avoid upsetting situations. They also have a low threshold for sensory discomfort and are preoccupied with details in their environment. [ref][ref]

People who score high on the HSP test will have the trait of Sensory Processing Sensitivity.

Note that sensory processing sensitivity isn’t quite the same as sensory processing theory, which is more concerned with behavioral changes to sensory stimulation. There is some overlap between the two, but SPS is more of an emotional response to sensory stimulation.[ref]

Back to SPS: A brain imaging study using fMRI showed that people with higher sensory processing sensitivity have differences that show up on imaging. The results showed that people with higher SPS had greater activation of brain regions involved in higher order visual processing. The authors concluded: “These results provide the first evidence of neural differences associated with SPS, the first direct support for the sensory aspect of this trait that has been studied primarily for its social and affective implications, and preliminary evidence for heightened sensory processing in individuals high in SPS.”[ref]

Sound and visual sensitivity:

Researchers looked at the overlap between people who were sensitive to visual stimuli, such as pattern glare sensitivity or photosensitivity in migraine, and sound sensitivity. They found that those who scored high on sensitivity to visual stimuli also scored higher on auditory discomfort from different sounds.[ref]

Gastrointestinal symptoms, and sensitivity to stress:

Highly sensitive people are more likely to have gastrointestinal symptoms such as abdominal pain, diarrhea, or indigestion. A study involving 863 Japanese adults found that sensory processing sensitivity correlates with gastrointestinal symptoms after controlling for sociodemographic characteristics.[ref]

Impacting work choices and burnout:

Being a dentist is a stressful job – you interact all day with people who are anxious and don’t want to be there. A study of dentists found that those who scored higher on the SPS scale were more likely to suffer from burnout and have their quality of life suffer.[ref]

Another study of nursing students found that they were more likely to score high on the HSP scale. While 15-20% of the general population scores as HSP, the percentage was 33% among nursing students. While the positive aspects of the trait, such as emotional sensitivity, fit well with nursing, the research study suggests that intervention strategies may help reduce stress and anxiety in nurses who score high on the HSP scale.[ref]

Genetic Research on Highly Sensitive People:

Genetic researchers estimate that SPS is about 47%-60% heritable, meaning that genetic variants are involved in this trait — along with life experiences.[ref][ref]

Psychological and behavioral traits are notoriously hard to pin down accurately in genetics studies, especially in smaller studies or studies that only involve one age group, sex, or race. I’m going to focus as much as possible on the variants that have been replicated.

Studies on heritability: 

One study of teenage twins, ages 15-17, looked at both anxiety sensitivity and environmental sensitivity. The study included 900 dizygotic twin pairs and 500 monozygotic twin pairs, with the goal of determining how much of a role genetics plays in environmental sensitivity.

The researchers administered assessments – the Children’s Anxiety Sensitivity Index and a 12-item Highly Sensitive Child (HSC) scale – to determine how sensitive the teens were to the environment and stress. They also included a “reported life events” assessment that looked at 20 items ranked by how unpleasant they were perceived to be. This life event scale included things like divorce, parental job loss, hospitalization, death of a friend, and failing an exam. All three assessments were then subjected to multivariable modeling.[ref]

The results showed that genetic influences accounted for about 60-75% of the phenotypic associations. In essence, environmental perception, or how negatively or positively someone viewed their environment, was due to both genetics (60-75%) and exposure to environmental influences (25-40%).

Another study of nearly 3,000 adolescent twins found that the heritability of sensitivity was 47%. The researchers also found that “genetic influences underlying sensitivity to negative experiences are relatively distinct from sensitivity to more positive aspects of the environment…”.[ref]

Now let’s take a look at the specific variants and pathways identified…

Lifehacks:

This is where I usually write about diet and supplements to help overcome a predisposition to a chronic disease or a vitamin deficiency. But for HSPs, I don’t think any ‘fixes’ are really needed. It’s just the way you’re wired – with pluses and minuses, just like everyone else.

Instead, I’ll offer some suggestions for minimizing the challenges.

Focus on the positive and minimize irritations:
One thing I’ve learned from reading extensively about genetic research is that our genetic diversity is all about tradeoffs. The genetic variants that make you more sensitive to your environment may make you better at empathizing with people or better at creating an aesthetically pleasing environment.

If you know you’re predisposed to be sensitive to noise and visual distractions, try to create a space in your home where you can relax and recharge. Play to your strengths and celebrate the positives of being an HSP while strategizing ways to minimize the negatives.

Be kind to children:
One of my personal takeaways from reading the research on HSPs is that highly sensitive children need to be treated with love and kindness. Several of the genetic variants for Sensory Processing Sensitivity were only significant when combined with negative parenting or negative childhood experiences.

COMT and Supplements:

For anyone with slow COMT function (rs4680, A/A), be sure to read about the interactions with methyl donor supplements and other commonly used natural supplements. With slower COMT enzyme function, the impact of changing dopamine levels with high-dose methylfolate or methylB12 for someone who is highly sensitive could cause irritability or anxiety.

Related article: COMT and methyl donor supplement interaction

Supplement Stack for Supporting Dopamine Synthesis:

Many of the variants related to HSP traits are in the dopamine pathways. Here are some ways to support dopamine synthesis, without going overboard and throwing everything out of balance.

Vitamin C to increase TH levels:
Tetrahydrobiopterin is a dopamine synthesis cofactor is not readily available as a supplement. However, vitamin C has been shown in multiple studies to increase BH4 levels under oxidative stress. This, in turn, increases dopamine levels and norepinephrine levels.[ref] Other studies in cell lines show that over time ascorbate (vitamin C) can increase TH levels.[ref]

Ginkgo biloba:
Multiple animal studies show that Ginkgo biloba increases dopamine in certain brain regions in animals.[ref] A clinical trial in older adults showed that Ginkgo biloba extract increased cognitive flexibility, which is associated with a mild enhancement of prefrontal dopamine.[ref]

Iron, only if low:
The tyrosine hydroxylase (TH) enzyme contains iron at its core. For someone very low in iron, decreased dopamine synthesis can occur.[ref][ref]

Always get a blood test to check iron and ferritin levels before supplementing with iron. (You can always order your own lab test if you don’t have a doctor to order the iron test for you.)  Too much iron can also cause mood issues due to oxidative stress in the brain and protein aggregation seen in neurodegenerative diseases. So you really don’t want to increase iron unless you’re actually low.

Related article: Iron overload genes

Zinc interaction:
Zinc and iron utilize the same transporters, so if you are taking a zinc supplement (or eating a meal that is rich in zinc), be sure to take iron supplements at a separate time for better absorption.

Vitamin B6:
The synthesis of dopamine also uses vitamin B6 (pyridoxal 5′-phosphate) as a cofactor. If you are low in B6, adding in a vitamin B6 or P5P supplement may help with dopamine synthesis.[ref] If you already have sufficient B6 levels, supplementing with it is unlikely to alter dopamine levels. While vitamin B6 is a water-soluble vitamin, it is also one that can cause rare cases of neuropathy when taken at high doses for long periods of time.

Related article: Vitamin B6 genes, absorption, and deficiency

Supplements for decreasing stress and anxiety:

If you’re a highly sensitive person stuck in an environment that you find stressful, you may want to look into the following supplements:

Ashwagandha:
A 60-day, randomized, double-blind, placebo-controlled study in adults found that 240 mg of ashwagandha extract (Shoden brand) twice daily decreased anxiety scores.[ref] A clinical trial for generalized anxiety disorder found that 1g/day of ashwagandha extract worked better than a placebo for decreasing anxiety scores.[ref]

Holy Basil:
This herbal supplement has been shown in animal studies to inhibit cortisol release. You can get Holy Basil as a supplement or drink it as Tulsi tea.[ref]

Genetic interactions to check:

If you are a highly sensitive person, here are some other genetic pathways that may interact and exacerbate your sensitivity to situations and your environment. Understanding these pathways may help you better tailor your environment and lifestyle to avoid being overwhelmed.

1. Check to see if you are more likely to feel anxious or jittery with caffeine (ADORA2A gene).
2. Check to see if you are genetically prone to higher levels of inflammation, which can be the root cause of depression or anxiety for some people.
3. Read about BDNF and supplements that support this flexibility factor for the brain.
4. If you have gastrointestinal issues, check out the article on IBS genes and see if there are positive steps you can take to mitigate the effects of stress on your gut.

Related articles and topics:

Anxiety: Genetics, heredity, and personalized solutions

Oxytocin Levels: Genetics of the Love Hormone