Sensory Processing Disorder

What is Sensory Processing Sensitivity? Traits, Insights, and ADHD Links

Sensory processing sensitivity is a trait that explains why up to 30 percent of people experience strong reactions to stimuli – strong smells, bright lights, other people’s moods, and even caffeine. Here, learn about the latest research on highly sensitive people, and how SPS compares to ADHD.

Close up of an eye taking in sensory stimuli

What is Sensory Processing Sensitivity?

Sensory processing sensitivity (SPS), or environmental sensitivity (ES), is a biologically-based trait characterized by increased awareness and sensitivity to the environment. A highly sensitive person — whether child or adult — processes sensory stimuli and information more strongly and deeply than do others. Individuals with SPS express these characteristics:

  • Deeper cognitive processing
  • More attention to subtleties
  • Greater emotional reactivity
  • Pausing before acting
  • Greater awareness of environmental and social stimuli, including the moods and emotions of others

What Does It Mean to Be a Highly Sensitive Person?

Researchers of various disciplines – from psychology, sociology, human development, biology, and more – have long recognized differing sensitivity levels among individuals. Dr. Elaine Aron, a clinical research psychologist who coined the term “the highly sensitive person” in her 1996 book (#CommissionsEarned), also developed a now widely used scale that measures responses to different stimuli. According to the scale, some markers of highly sensitive people (HSPs) include:

  • Needing to withdraw (privacy from stimulation)
  • Being easily overwhelmed by bright lights, strong smells, loud noises, clothing materials, and other stimuli
    Being affected by other people’s moods
  • Feeling annoyed or overwhelmed when asked to do too many things at once
  • Becoming nervous when observed performing a task
  • Sensitivity to caffeine

A Highly Sensitive Child Scale is also available and used. This scale divides behaviors into three distinct components of SPS. Discomfort with loud noises, for example, is associated with a low sensory threshold. Nervousness when having to do multiple tasks in a short amount of time is linked to ease of excitation. Responding to pleasant stimuli, like music, scent, and scenery, is associated with aesthetic sensitivity.

[Hypersensitivity Is Real: Why Highly Sensitive People Have ADHD]

Is Sensory Processing Sensitivity a Disorder?

SPS is not a disorder, but rather an innate trait. It should not be confused with sensory processing disorder (SPD), wherein the brain has difficulty organizing and processing sensory stimuli. SPS, in comparison, is not associated with dysregulation, but with awareness, depth of processing, and needing time to process information and stimuli.

Sensory Processing Sensitivity: Prevalence and Origins

Early studies estimate that 20 percent of the population may be “highly sensitive.”1 Researchers sometimes refer to highly sensitive people as orchids, given the flower’s responsiveness to changes in its environment. Less sensitive people, on the other hand, are referred to as dandelions.

More recent research, however, suggests that there may be three groups of sensitive people2. About 40 percent of people in this framework fall into a moderately sensitive group (tulips). Low-and high-sensitive individuals each make up about 30 percent of individuals. Research appears to be pointing to sensitivity as a continuum rather than having definitive categories. This theory encourages considering environmental factors in tandem with biology when studying how sensitivity manifests (genetic research suggests, for example, that about 50 percent of sensitivity is heritable3).

[Read: “My Socks Feel Weird!” Morning Help for the Highly Sensitive Child]

Sensory Processing Sensitivity and the Brain

Recent research points to unique neural activity among highly sensitive people.

Our 2014 fMRI study found that the anterior insula, a part of the brain associated with emotional processing and visceral sensations (like the gut feelings that often accompany empathy), shows higher activation in highly sensitive people4. The study, in part, had participants look and react to images of partners and strangers experiencing a range of positive and negative emotions.

The highly sensitive participants who looked at happy images of their partners, furthermore, had more brain activation in areas related to bodily sensations. Seeing a partner smile, or reflecting on a partner’s happiness, led to greater activation in the ventral tegmental area (VTA), a key dopamine area of the brain also associated with motivation, energy, feelings of euphoria, and reward. Seeing sad images of their partners activated areas of the brain linked to cognitive processing, reflective thinking, and perspective.

In another study5, we found that highly sensitive individuals who also reported a positive childhood experience showed even greater VTA activity after seeing positive images. In response to negative images, these individuals, interestingly, showed activation in areas associated with self-regulation and cognitive processing. VTA activity, meanwhile, showed decreased activity in response to negative images for those with negative childhood experiences.

Sensory Processing Sensitivity and ADHD

Sensory processing sensitivity and attention deficit hyperactivity disorder (ADHD or ADD) do overlap in some ways. Both are characterized, in part, by emotional reactivity and overstimulation. The risk for anxiety and mood disorders is greater, especially if a sensitive person experienced a negative childhood. ADHD and SPS can also impact interpersonal and academic performance. They are, however, inherently different.

ADHD is a neuropsychiatric disorder characterized by inattention, hyperactivity, and/or impulsivity. Sensory processing sensitivity, meanwhile, is proposed to be a biological temperament trait observed in people who are more sensitive to environmental and social stimuli. A child with ADHD, for example, may display impulsivity in response to an overwhelming environment, but a sensitive child would more likely pause and reflect before taking action.

Brain activity also delineates the difference between the two. ADHD is associated with less activation in cognitive processing areas that impact self-regulation, attention, and inhibition. With SPS, there is actually more activation in these areas, along with depth of processing and empathy.

Sensory Processing Sensitivity Interventions

Despite overlapping characteristics, it is possible to have SPS and ADHD. For individuals with ADHD who suspect SPS, it is important to consider the extent and length of responses to stimuli, as well as the aforementioned core characteristics of SPS (like being reflective, more empathetic, and careful to act), especially as they may have manifested in childhood. Interventions can include:

  • Taking the Highly Sensitive Person Scale, also available on the LoveSmart app
  • Keeping calm and comfortable environments
  • Decreasing sugar and caffeine intake
  • Engaging in activities that build resilience, self-esteem, and self-regulation (e.g. meditation, yoga, and talk-therapy)

The content for this article was derived from the ADDitude Expert Webinar “Why Are You So Sensitive? Understand How Sensory Processing Sensitivity Affects the ADHD Brain” with Bianca Acevedo, Ph.D., which was broadcast live on November 18, 2020.

Sensory Processing Sensitivity: Next Steps

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1 Boyce, W. T., & Ellis, B. J. (2005). Biological sensitivity to context: I. An evolutionary-developmental theory of the origins and functions of stress reactivity. Development and psychopathology, 17(2), 271–301.

2 Lionetti, F., Aron, A., Aron, E.N. et al. Dandelions, tulips and orchids: evidence for the existence of low-sensitive, medium-sensitive and high-sensitive individuals. Transl Psychiatry 8, 24 (2018).

3 Assary, E., Zavos, H.M.S., Krapohl, E. et al. Genetic architecture of Environmental Sensitivity reflects multiple heritable components: a twin study with adolescents. Mol Psychiatry (2020).

4 Acevedo, B. P., Aron, E. N., Aron, A., Sangster, M. D., Collins, N., & Brown, L. L. (2014). The highly sensitive brain: an fMRI study of sensory processing sensitivity and response to others’ emotions. Brain and behavior, 4(4), 580–594.

5 Acevedo, B. P., Jagiellowicz, J., Aron, E., Marhenke, R., & Aron, A. (2017). Sensory processing sensitivity and childhood quality’s effects on neural responses to emotional stimuli. Clinical Neuropsychiatry: Journal of Treatment Evaluation, 14(6), 359–373.