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Sensory defensiveness is a condition defined as having "a tendency to react negatively or with alarm to sensory input which is generally considered harmless or non-irritating" to neurotypical people.
It is not uncommon for individuals to have a few mild sensory defensive traits. However, when multiple defensive traits impact the person's day-to-day life, that person is considered to be sensory defensive.
Common symptoms of sensory defensiveness include intolerance of high-pitched noises, intolerance of chewing sounds, intolerance of overhead lights (especially fluorescent lighting); experiencing a feeling of being attacked upon being touched (especially from light touch or sudden touch); intolerance of certain types of fabrics in contact with the skin; becoming nauseated upon smelling something that does not smell bad to neurotypical individuals; difficulty maintaining eye-contact; severe intolerance of foods due to taste, texture, or temperature; and generally becoming overwhelmed when exposed to a lot of sensory stimuli at once.
Intolerance in this context should not always be taken as unwillingness to be subject to the sensory stimuli in question; rather, intolerance is an inability to process the sensory stimuli in any way other than as over-stimulating, because the sensory stimuli provokes a fight-or-flight reaction. This is also known as sensory overload.
Sensory defensiveness can vary between individuals:
- The senses that are problematic for one person may not be so for another. (Commonly, individuals report major issues with two or three senses and minor issues with the other senses.)
- How easily and the way in which a particular sense bothers individuals varies (e.g. high-pitched noises may annoy someone, or they may hurt his/her ears; touch may provoke anxiety, or it can be painful).
- The triggers for a particular sense vary between people (e.g. one person may be sensitive to the texture of mushy foods, while another may be sensitive to crunchy foods).
There are believed to be multiple etiologies for sensory defensiveness, including genetic factors, environmental conditioning, drug or alcohol abuse, sexual abuse, or premature birth. Those diagnosed with attention deficit hyperactivity disorder report much higher than average rates of hypersensitivity to sensory stimulus. Autism also increases hypersensitivity, especially to sound. Additionally, stress of any kind usually increases sensitivity to sensory stimuli. Stress due to reactions to sensory input can cause a chain reaction, leading to a meltdown, as described below.
Effects and treatment 
Sensory overload can lead to what is commonly termed a "meltdown". This may look much like a tantrum, or a person may undergo dissociation, which causes individuals to withdraw into themselves. Individuals will often cope with their sensory difficulties by avoiding those situations that cause them irritation. Occupational therapists often prescribe "sensory diets". This is a therapy that is tailored to the individual in which one experiences calming sensory stimuli that help to balance the sensory system. Snoezelen rooms, in which sensory experiences can be controlled and explored, are sometimes used. Individuals will often naturally create or find their own calming sensory stimuli (stims) or sensory diets.
The other side to these issues is that many people report a positively heightened awareness of their senses, under the right conditions. They also promote "stims", which can include music, exercise, and any other pleasing sensory stimulation, as natural means of reducing stress.
Component of other disorders 
Sensory defensiveness is a subset of sensory integration dysfunction. Sensory integration dysfunction is considered a symptom of the autism spectrum, but a person does not have to display other autistic traits to have sensory defensiveness or sensory integration dysfunction. Sensory integration dysfunction and defensiveness are also common with developmental dyspraxia, cerebral palsy, and fetal alcohol syndrome.
- Wilbarger, Patricia and Wilbarger, Julia. (1991). Sensory Defensiveness in Children Aged 2-12: An Intervention Guide for Parents and Other Caretakers.
- Kinnealey M, Oliver B, Wilbarger P (1995). "A phenomenological study of sensory defensiveness in adults". Am J Occup Ther 49 (5): 444–51. PMID 7598160.
- Johnson, Mary Jane. Having ADD and Being Hypersensitive: Is There A Connection? Attention Deficit Disorder Association (1998). Retrieved on 2007-11-27.
- Erissandra Gomes, Fleming Salvador Pedroso & Mario Bernardes Wagner (October–December 2008). "Auditory hypersensitivity in the autistic spectrum disorder". Pro-fono : revista de atualizacao cientifica 20 (4): 279–284. PMID 19142473.
- Sensory Integration Therapy for Cerebral Palsy. About cerebral palsy. Retrieved on 2007-11-27.
- Malbin, D (1993). Fetal Alcohol Syndrome, Fetal Alcohol Effects: Strategies for Professionals. Center City, MN: Hazelden. ISBN 0-89486-951-5.
Further reading 
- Bogdashina, Olga. Sensory Perceptual Issues in Autism and Asperger's Syndrome: Different Sensory Experiences, Different Perceptual Worlds. An overview of sensory traits in the autism spectrum.
- Heller, Sharon. Too Loud, Too Bright, Too Fast, Too Tight: What to Do If You Are Sensory Defensive in an Overstimulating World (ISBN 0-06-093292-9)
- Moore, Karen. The Sensory Connection Program: Activities in Mental Health Treatment. Symptoms, background information, and treatment of Sensory Defensiveness in adults
- Wilbarger, Patricia and Julia. Sensory Defensiveness in Children Aged 2–12: An Intervention Guide for Parents and Other Caretakers. Explains the roots of sensory defensiveness in children.
- Separating Fact from Fiction in the Etiology and Treatment of Autism - A Scientific Review of the Evidence[not relevant]
- Why "Sensory Integration Disorder" Is a Dubious Diagnosis