Sensory experiences and overload

Research describes three broad patterns. In over-responsivity, ordinary sounds, lights, textures or smells feel too strong or unpleasant. In under-responsivity, a person reacts little or late, for example to their name being called or to pain. In sensory seeking, a person looks for more of some kind of input. A meta-analysis of 55 questionnaire studies found large differences between autistic and non-autistic people on all three, with wide variation between studies. Compared with other clinical groups, only over-responsivity stood out.¹ How common these differences are, and the theories about why they happen, are covered in Sensory processing and prediction.

Many people do not fit one pattern. Two independent research groups sorted caregivers' questionnaire answers about autistic children into a few subtypes that differ mainly in how marked the differences are and partly in which pattern or sense leads.^2,3 In one, of 228 children aged 2 to 10, the four subtypes differed in how marked the differences were and, for two of them, in which senses led (taste and smell; movement and body position). Age, gender, IQ and autism severity did not explain them well.² In the other, a US survey of 1,294 children aged 2 to 12, the four subtypes ran from a mild group to an "extreme-mixed" group high on several patterns at once, and they did differ by age, gender, autism severity and family income and education. On the authors' model, 91% of children were in the same subtype a year later.³

In one Australian study of 919 autistic children aged 3 to 14, mostly boys, that compared age groups at a single time point, sensitivity and avoidance were most common in middle childhood, while under-responsivity and seeking showed little difference by age. Boys and girls had similar overall profiles; girls showed more sensitivity, a finding from this one study. Its first author also led the 228-child study.⁴

In a survey of 49 autistic adults designed with autistic people, participants described over-responsivity across many senses, including sounds that were too loud and painful.⁵ Under-responsivity was reported mostly for signals from the body. Of the 40 who answered a checklist, 30% reported it for pain, 15% for heat and 12.5% for cold. Many described a high pain threshold, and one said a partner noticed their shivering before they felt cold.⁵

Most of these adults sought soothing input, such as music, certain textures or firm pressure, to cope with distress. Whether a sensation felt enjoyable or aversive depended on how much control they had over it and how predictable it was. Several said they tolerated more when relaxed or rested and less when stressed or tired.⁵ Some linked their sensory seeking to self-harm or eating disorders.⁵

In focus groups with 18 autistic adults, sensitivity to light, motion, patterns and colors led to tiredness and stress and got in the way of travel and social life. Understanding their own visual experiences made participants less worried about them.⁶ In instant-message interviews with nine adults diagnosed with Asperger syndrome, sensory stress could build into what the authors called a "stress avalanche", and the same heightened senses were also a source of fascination.⁷

A systematic review of 11 studies found atypical sensory processing in 82 to 97% of autistic children, depending on the study. Sensory differences went with lower adaptive behavior, but the studies could not show which way the link runs.⁸ A second review, of 7 studies of children aged 5 to 13 that used one common framework for sensory processing, found it linked to taking part in daily activities. The level of that evidence was medium to low.⁹

One study followed 51 autistic children and 30 children with other developmental disabilities from an average age of about 5.6 to 9. Across both groups there was some evidence that earlier sensory features predicted lower adaptive behavior later, with results that varied by group and by measure.¹⁰ In the national survey described above, children in an under-responsive, preoccupied subtype had the lowest adaptive behavior, and children in the extreme-mixed subtype the most behavior difficulties and parenting stress.¹¹ Both studies come from the same research group.

Sensory differences also go with sleep and eating. In 1,347 autistic children seen in a clinical network, over-responsivity correlated with sleep problems, with small effects. Once anxiety was taken into account, some of these links dropped out, and which ones differed by age.¹² Among 53 autistic children aged 3 to 11, those with atypical oral sensitivity refused more foods and ate fewer vegetables than other autistic children.¹³

In 66 autistic adults aged 20 to 38 without intellectual disability, studied in Taiwan, quality of life was lower than in non-autistic adults in every area measured, and sensory sensitivity predicted lower physical and psychological quality of life.¹⁴ In an online survey of 296 autistic adults, 58.4% of them women, 24.3% non-binary or another gender and 15.9% men, unpleasant sound environments statistically accounted for part of the link between autistic traits and the impact of sound sensitivity on quality of life. Nearly three in four (73.5%) used earplugs and headphones.¹⁵

Clothing is one everyday route. In 86 autistic adults in the UK, more sensitivity to the feel of clothing went with more dissatisfaction with appearance, and its link with lower self-esteem depended on how dissatisfied they were with how they looked.¹⁶ In a qualitative study of six autistic adults, which also tracked where they went by GPS, those with sensitive or avoiding profiles described some places as overwhelming and tiring, and spent less time out in the community.¹⁷

One study looked at long-term physical conditions, which is a different question from the illness some autistic writers describe after a heavy sensory day (see the community section below). Among 973 autistic adults in the Netherlands, most of them women, 21% reported a diagnosed central sensitivity syndrome and 60% scored at or above the cut-off for one; women reported more diagnoses and symptoms than men. Sensory sensitivity and anxiety statistically accounted for the whole link between autistic traits and these symptoms. The study had no non-autistic comparison group.¹⁸

Misophonia was the subject of a large survey of autistic adults. Among 1,050 autistic adults who completed a misophonia scale, a higher proportion reported moderate-to-extreme symptoms than in previously reported general-population samples, though the comparison was with figures from earlier studies, not a matched non-autistic group. Female participants, and those with co-occurring conditions, scored higher on the misophonia scale, a finding from this one survey. In the same survey, autistic traits predicted more misophonia symptoms once age, sex and co-occurring conditions were allowed for, and sensitivity to sound and to light each statistically accounted for part of that link; the study was cross-sectional, so it cannot show which comes first. Misophonia also comes up in Monotropism.³³

Smell is one of the least-studied senses in autism research, though it matters for noticing danger, judging whether food is safe and connecting with other people.³⁴ A preregistered meta-analysis pooled 46 studies with 1,580 autistic and 7,698 non-autistic people of all ages. On standardized tests, autistic people scored lower on average. The difference was clearest for naming a smell (odor identification) and smaller for detecting a faint one (threshold), and it was larger in studies of children than in studies of adults.³⁴ Some smaller studies point the other way: in one, 17 autistic men detected a smell from further away than 17 non-autistic men, and in another study of 18 autistic and 18 non-autistic children, the autistic children's automatic sniffing did not change with how pleasant a smell was, though they reported smelling it the same as the other children.^35,36

On self-report, and on ratings of how pleasant a smell seemed, the groups did not differ, and the widest gap came from caregivers: asked about a person's sense of smell and taste, they rated autistic people much lower than the tests did.³⁴ Tests, self-reports and caregiver reports measure different things, so a lower test score does not by itself mean a person notices less in daily life.³⁴ Because the pooled studies are mostly cross-sectional, the finding is a group average, with wide overlap between autistic and non-autistic people. How strongly smells are felt (finding them too strong) is covered with the other senses in the first section.

In the survey of 49 autistic adults, some described being overwhelmed in busy places with many kinds of input at once, which could end in disengaging or "shutdown".⁵ When 32 autistic adults were asked about meltdowns, most described being overwhelmed by information, by their senses, and by social and emotional stress. They described extreme emotion, trouble thinking and remembering, and feeling unlike themselves. Many described the meltdown as a release. They tried to avoid triggers, or to be alone when a meltdown seemed close, to avoid harm to themselves and their relationships.¹⁹

Eight autistic children and young people aged 8 to 18 in Toronto, interviewed about burnout, inertia, meltdown and shutdown, named meltdowns as the most common, and said neurotypical adults such as parents and teachers often misunderstood them.²⁰ In a study that drew a definition of autistic burnout from interviews with US autistic adults and from public online accounts, reduced tolerance of sensory input was one of its three main features, alongside chronic exhaustion and loss of skills.²¹

In focus groups with 24 autistic adults, supermarkets and restaurants or cafés were most often named as disabling, followed by high streets, public transport, health care settings and shops. Outdoor spaces, museums and cinemas were named as easier, and shops appeared on both lists. The counts were small, at most 10 of the 24 people for any place.²² The authors drew out six things that make a place easier or harder: the sensory landscape, space, predictability, understanding from other people, adjustments, and room to recover.²² In a Swedish survey, 62 autistic adults, most diagnosed in adulthood, reported more discomfort with background sound in health care settings than 36 non-autistic adults did, and sound and closeness to other people bothered them most.²³ A review of building design recommends simple layouts, zoned spaces, retreat spaces, dimmable light, sound absorption, plain colors, and spaces that can be adjusted for each person.²⁴ These are recommendations; most have not been tested for their effects.

The clearest test is in dental care. In a randomized crossover trial, 162 autistic children aged 6 to 12, 84% of them boys, were randomized and 138 completed both visits. Each had one cleaning in an ordinary room and one in a sensory-adapted room: overhead lights off, calming pictures projected on the ceiling, calming music and a weighted wrap. In the adapted room their skin conductance level, a sign of arousal, was lower, and video showed less distress, though the video coders knew which room they were watching. Another skin conductance measure and questionnaire measures did not differ, Age, IQ, how well children could express themselves and how over-responsive they were changed how much the room reduced visible distress: it helped younger children, and those with lower IQ, less expressive language or more over-responsivity, the most.²⁵ An earlier pilot from the same group, with 22 autistic children, found lower physiological anxiety in the adapted room, though only about half the children completed the self-reports on pain and discomfort. The 22 non-autistic children in the pilot also benefited.²⁶ An earlier systematic review rated the evidence for sensory changes to the dental environment as moderate, on the strength of a single study of autistic children.³¹ A 2024 review of nine randomized trials of dental adaptations, which included the large trial, concluded that sensory-adapted rooms and video modeling both reduced distress.²⁷

Elsewhere the studies are very small. Sound-absorbing walls and then new lighting in one classroom were followed by more attending in four male students aged 13 to 20 with autism or dyspraxia, with no return to the original classroom to check.²⁸ In six children aged 8 to 16 with autism and sound sensitivity, noise-reducing headphones lowered skin conductance compared with each child's own baseline, though the wristband data also became more reliable in later phases.²⁹ Neither study had a control group.

Many autistic writers describe sensory overload as being flooded. Devon Price writes that "When an Autistic person is flooded with upsetting sensory information for too long, they enter a state of sensory overload", which can look like a tantrum, a shutdown, a meltdown, or confused, scripted answers.^c1 Price also argues that, for autistic people, a stimulus bothers them more the longer it goes on, and that intense input is felt "as if it were physical pain".^c1 Sarah Nannery takes up a description she has heard, "living life with the volume turned all the way up", and adds that overload can also come in a quiet place after a hard week, when one small thing becomes the "final grain of sand" that tips her into overload.^c3

Writers describe two directions that overload can take. Nannery describes it as outward, like an explosion, or inward, like depression.^c3 Price describes shutdown as the quieter counterpart of a meltdown, a way of dissociating that can look like suddenly falling asleep or zoning out.^c2 Daniel Jones describes being over-sensitive to one sense and under-sensitive to another, for example disliking light touch while enjoying loud music.^c5

Touch has a pattern of its own for many autistic writers. Autistic contributors to Is This Autism?, a clinicians' guide by Donna Henderson, Sarah Wayland and Jamell White, describe light touch as alarming and firm touch as calming; Noelle B. writes, "Deep touch is more soothing to me, like a weighted blanket or long mutual hug."^c11 Luke Beardon, an autism educator, finds a preference for firm touch over soft "quite common", and writes that deep pressure can be "a source of great comfort" for some people, though "it will not be to everyone's taste".^c12 Daniel Burford, an autistic writer, is among those it does not help: "Weighted blankets overwhelm me."^c13 Burford tells readers for whom deep pressure does nothing that "you haven't failed at being autistic".^c13

Several writers describe proprioception, the sense of where the body is and how it is moving. Beardon writes that when this sense does not help a person "automatically judge distance", they may have to work out consciously where to stand, and that a tight belt can give some people "a better physical sense of self".^c12 Fabian B., another contributor to the clinicians' guide, writes that posture is never automatic: "I find I must manually 'put everything in the right place.'"^c14 Tee Mone't writes that "sensory overload causes me to lose all spatial and body awareness", so that stimming no longer works to release the pressure.^c16

Megan Anna Neff names an aftermath. After days working in hospitals and universities she came home tired and with a low-grade fever, and realized "I was experiencing sensory overload to such a degree that my body was interpreting it as a physical illness"; she and her child call this being "sensory sick".^c4 Neff also separates sensory overload, which comes from what is happening now, from anxiety about what might happen, and from "sensory dread", which she takes from psychologist Jonathan Dalton: anticipating a place known to cause overload, such as a mall or a dentist.^c4

Several writers say these experiences were long dismissed. Megan Griffith lists the expectation that "You must not be bothered, upset, or hurt by sensory experiences that are commonplace" among the pressures of neuronormativity.^c6 Price writes that "Entire generations of Autistic people lived their lives being told that their pain didn't exist."^c7 Price also describes "divergent design", Marta Rose's idea that a home should suit how its autistic occupant actually lives, and argues that disability law should cover sensory access.^c8,c9 Steve Silberman records an early example of autistic-designed space: at Autreat, a retreat run by autistic people, color-coded badges let people signal whether they wanted to be approached.^c10

Carly Jones, an autistic advocate for autistic girls, argues that "Sensory issues are an accessibility need that cause great physical pain", as a classroom without a ramp would be for a wheelchair user.^c17

April Herren, who cannot speak and types on a letterboard with a trained helper's support (facilitated communication), writes in the anthology Loud Hands: "I can't tell where my body is in relation to things."^c15 Herren describes needing to "continually feel my surroundings" to know where the body fits in a place.^c15

Amy Sequenzia, who types to communicate, recalls that after second-degree burns on her arm, someone who saw no pain on her face said she "did not feel pain". She writes: "I do, but my face does not show the intensity of the pain."^c18 Huan Vuong, who now spells on a letterboard, describes a helicopter overhead whose "sounds attack my ears", leaving him unable to communicate.^c19