It is estimated that up to 16.5% of elementary school aged children present elevated SOR behaviors in the tactile or auditory modalities. However, this figure might represent an underestimation of Sensory Over Responsivity prevalence, since this study did not include children with developmental disorders or those delivered preterm, who are more likely to present it.

This figure is, nonetheless, larger than what previous studies with smaller samples had shown: an estimate of 5–13% of elementary school aged children.

Incidence for the remaining subtypes is currently unknown.

There is a growing evidence base that points to and supports the notion that adults also show signs of sensory processing difficulties. In the United Kingdom early research and improved clinical outcomes for clients assessed as having sensory processing difficulties is indicating that the therapy may be an appropriate treatment. The adult clients show a range of presentations including autism and Asperger's syndrome, as well as developmental coordination disorder and some mental health difficulties. Therapists suggest that these presentations may arise from the difficulties adults with sensory processing difficulties encounter trying to negotiate the challenges and demands of engaging in everyday life. It is important when treating adults not only to focus upon sensory regulation but to also help them develop and maintain social supports. Adults who are sensory over-responsive have very high correlated anxiety and depression levels compared to adults who do not have sensory over-responsiveness. This is correlated to the perceived absence of social supporters. Sensory processing disorder can also be correlated with sleep quality in adults. This correlation can be seen especially in adults who have low neurological thresholds (sensory sensitivity and sensory avoidance). These individuals are more sensitive to tactile, auditory and visual stimuli which often impacts their quality of sleep.

Sensory dysfunction disorder is a reported neurological disorder of information processing, characterized by difficulty in understanding and responding appropriately to sensory inputs. Sensory dysfunction disorder is not recognized by the American Medical Association. "Sensory processing (SP) difficulties have been reported in as many as 95% of children with autism, however, empirical research examining the existence of specific patterns of SP difficulties within this population is scarce."

The brain receives messages from the body's sensory systems, which informs the brain of what is going on around and to a person's body. If one or more of these systems become overstimulated, it may result in what is known as Sensory Dysfunction Disorder. An example of a response to overstimulation is expressed by A. Jean Ayres, in "Sensory Integration and the Child: Understanding Hidden Sensory Challenges". She writes, "When the flow of sensations is disorganized, life can be like a rush-hour traffic jam” (p. 289). The following sensory systems are broken down into individual categories to better understand the impact a sensitivity can have on an individual.

Auditory processing disorder (APD), also known as central auditory processing disorder (CAPD), is an umbrella term for a variety of disorders that affect the way the brain processes auditory information. Individuals with APD usually have normal structure and function of the outer, middle and inner ear (peripheral hearing). However, they cannot process the information they hear in the same way as others do, which leads to difficulties in recognizing and interpreting sounds, especially the sounds composing speech. It is thought that these difficulties arise from dysfunction in the central nervous system.

The American Academy of Audiology notes that APD is diagnosed by difficulties in one or more auditory processes known to reflect the function of the central auditory nervous system.

APD can affect both children and adults, although the actual prevalence is currently unknown. It has been suggested that males are twice as likely to be affected by the disorder as females, but there are no good epidemiological studies.

Developmental coordination disorder is a lifelong neurological condition that is more common in males than in females, with a ratio of approximately four males to every female. The exact proportion of people with the disorder is unknown since the disorder can be difficult to detect due to a lack of specific laboratory tests, thus making diagnosis of the condition one of elimination of all other possible causes/diseases. Approximately 5–6% of children are affected by this condition.

The frequency of phantosmia is rare in comparison with the frequency of parosmia. Parosmia has been estimated to be in 10-60% of patients with olfactory dysfunction and from studies, it has been shown that it can last anywhere from 3 months to 22 years. Smell and taste problems result in over 200,000 visits to physicians annually in the US. Lately, it has been thought that phantosmia might co-occur with Parkinson's disease. However, its potential to be a premotor biomarker for Parkinson's is still up for debate as not all patients with Parkinson's disease have olfactory disorders

Even though the causes of dysosmia are not yet clear, there are two general theories that describe the etiology: the peripheral and central theories. In parosmia, the peripheral theory refers to the inability to form a complete picture of an odorant due to the loss of functioning olfactory receptor neurons. The central theory refers to integrative centers in the brain forming a distorted odor. In phantosmia, the peripheral theory refers to neurons emitting abnormal signals to the brain or the loss of inhibitory cells that are normally present in normal functioning. The central theory for phantosmia is described as an area of hyper-functioning brain cells that generate the order perception. Evidence to support these theories include findings that for the majority of individuals with distortions, there is a loss of sensitivity to smell that accompanies it and the distortions are worse at the time of the decreased sensitivity. It has been reported in parosmia cases that patients can identify triggering stimuli. Common triggers include gasoline, tobacco, coffee, perfum, fruits and chocolate.

The cause of dysosmia has not been determined but there have been clinical associations with the neurological disorder:

- Upper respiratory tract infection (URTIs)

- Nasal and paranasal sinus disease

- Toxic chemical exposure

- Neurological abnormalities

- Head trauma

- Nasal surgery

- Tumors on the frontal lobe or olfactory bulb

- Epilepsy

Most of cases are described as idiopathic and the main antecedents related to parosmia are URTIs, head trauma, and nasal and paranasal sinus disease. Psychiatric causes for smell distortion can exist in schizophrenia, alcoholic psychosis, depression, and olfactory reference syndrome.

There have not been sufficient studies conducted to make conclusive statements about prevalence nor who tends to suffer EHS. One study found that 13.5% of a sample of undergrads reported at least one episode over the course of their lives, with higher rates in those also suffering from sleep paralysis.

It has been discovered that APD and ADHD present overlapping symptoms. Below is a ranked order of behavioral symptoms that are most frequently observed in each disorder. Professionals evaluated the overlap of symptoms between the two disorders. The order below is of symptoms that are almost always observed. This chart proves that although the symptoms listed are different, it is easy to get confused between many of them.

There is a high rate of co-occurrence between AD/HD and CAPD. Research shows that 84% of children with APD have confirmed or suspected ADHD. Co-occurrence between ADHD and APD is 41% for children with confirmed diagnosis of ADHD, and 43% for children suspected of having ADHD.

Trauma, in general, appears to be an important factor, due to the fact that PRS is also repeatedly seen in refugees and witnesses to violence. The helplessness and hopelessness can transmit from parents to children and from children to parents as they watch one another battling with uncontrollable proceedings. Viral infections are repeatedly seen to be a factor in PRS; many cases are thought to begin with a viral infection. There have been other theories regarding the cause of PRS, for instance, the psychodynamic theory of fatal mothering and a potential neurobiological role of the insula. Von Folsach and Montgomery put forth four essential risk factors: (1) a premorbid personality, (2) a history of child psychiatric problems, (3) parental psychiatric problems and (4) sudden stressful events. PRS children are typically known to be perfectionists, conscientious and high achievers. When these children are put in stressful events that they feel they cannot control, they go into a state of learned helplessness. Previous child psychiatric problems can designate a susceptibility to develop PRS when put in stressful situations, and parental psychiatric problems may influence the parents' capability to support and care for their children.

Sensory processing sensitivity (SPS), a personality trait, a high measure of which defines a highly sensitive person (HSP), has been described as having hypersensitivity to external stimuli, a greater depth of cognitive processing, and high emotional reactivity. The terms SPS and HSP were coined in the mid-1990s by psychologists Elaine Aron and husband Arthur Aron, with SPS being measured by Aron's Highly Sensitive Person Scale (HSPS) questionnaire. Other researchers have applied various other terms to denote this responsiveness to stimuli that is evidenced in humans and other species.

According to the Arons and colleagues, people with high SPS comprise about 15–20% of the population and are thought to process sensory data more deeply due to the nature of their central nervous system. Although many researchers consistently related high SPS to negative outcomes, Aron and colleagues state that high SPS is a personality trait and not a disorder; other researchers have associated it with increased responsiveness to both positive and negative influences.

Pervasive refusal syndrome is for the most part frequently seen in girls and less so in boys. The average age of onset is between the ages of 7 and 15. Affected children are usually high achievers with high self-expectations, fears of failure, and difficulty dealing with failure to achieve personal standards. The onset of PRS is usually acute.

As of 2014, no clinical trials had been conducted to determine what treatments are safe and effective; a few case reports had been published describing treatment of small numbers of people (two to twelve per report) with clomipramine, flunarizine, nifedipine, topiramate, carbamazepine, methylphenidate. Studies suggest that education and reassurance can reduce the frequency of EHS episodes. There is some evidence that individuals with EHS rarely report episodes to medical professionals.

Investigators have successfully narrowed down the major factors that are associated with musical hallucinations. Evers and Ellgers compiled a significant portion of musical hallucination articles, case studies etc. and were able to categorize five major etiologies:

- Hypoacusis

- Psychiatric disorders

- Focal brain lesion

- Epilepsy

- Intoxication

There is no cure for the condition. Management is through therapy.

Hypoacusis is defined as impairment in hearing or deafness. Hypoacusis is one of five etiologies of musical hallucinations, and is the most common in the case studies reviewed by Evers and Ellgers. According to Sanchez et al. 2011, there have been suggestions that pontine lesions could alter the central auditory system's function causing hypoacusis and musical hallucinations.

The tactile system is the sense of touch. Someone with Sensory Dysfunction Disorder may have symptoms of not being able to process any form of physical connection. Conversely, a person may need to have some sort of physical connection to soothe an anxiety he or she is experiencing.

Brain related causes are less commonly associated with isolated vertigo and nystagmus but can still produce signs and symptoms, which mimic peripheral causes. Disequilibrium is often a prominent feature.

- Degenerative: age related decline in balance function

- Infectious: meningitis, encephalitis, epidural abscess, syphilis

- Circulatory: cerebral or cerebellar ischemia or hypoperfusion, stroke, lateral medullary syndrome (Wallenberg's syndrome)

- Autoimmune: Cogan syndrome

- Structural: Arnold-Chiari malformation, hydrocephalus

- Systemic: multiple sclerosis, Parkinson's disease

- Vitamin deficiency: Vitamin B12 deficiency

- CNS or posterior neoplasms, benign or malignant

- Neurological: Vertiginous epilepsy, abasia

- Other – There are a host of other causes of dizziness not related to the ear.

- Mal de debarquement is rare disorder of imbalance caused by being on board a ship. Patients suffering from this condition experience disequilibrium even when they get off the ship. Typically treatments for seasickness are ineffective for this syndrome.

- Motion sickness – a conflict between the input from the various systems involved in balance causes an unpleasant sensation. For this reason, looking out of the window of a moving car is much more pleasant than looking inside the vehicle.

- Migraine-associated vertigo

- Toxins, drugs, medications; it is also a known symptom of carbon monoxide poisoning.

Boterberg "et al." (2016) describe high SPS as a "temperamental or personality trait which is present in some individuals and reflects an increased sensitivity of the central nervous system and a deeper cognitive processing of physical, social and emotional stimuli".

People with high SPS report having a heightened response to stimuli such as pain, caffeine, hunger, and loud noises. According to Boterberg "et al.", these individuals are "believed to be easily overstimulated by external stimuli because they have a lower perceptual threshold and process stimuli cognitively deeper than most other people." This deeper processing may result in increased reaction time as more time is spent responding to cues in the environment, and might also contribute to cautious behavior and low risk-taking.

The HSP Scale, initially (1997) a questionnaire designed to measure SPS on a unidimensional scale, was subsequently decomposed into two, three, or four factors or sub-scales. Most components have been associated with traditionally-accepted negative psychological outcomes including high stress levels; being easily overwhelmed; increased rates of depression, anxiety, and symptoms of autism; sleep problems; and more physical health problems; the diathesis-stress model focused on increased vulnerability to negative influences. However, the differential susceptibility theory (DST) and biological sensitivity to context theory (BSCT) and sensory processing sensitivity (SPS) suggest increased plasticity (responsiveness) to both positive and negative influences; and the sensitivity (VS) concept emphasizes increased responsiveness to positive experiences. Smolewska "et al." (2006) said that in their research, positive outcomes were more common in individuals with high aesthetic sensitivity, who tend to experience heightened positive emotions in response to rewarding stimuli and more likely to score high on "openness" on the Big Five factors model.

Research in evolutionary biology provides evidence that the trait of SPS can be observed, under various terms, in over 100 nonhuman species, Aron writing that the SPS trait is meant to encompass what personality psychologists have described under various other names. Conversely, Aron has distinguished SPS from what she considers it is not, explicitly distinguishing high SPS from possibly-similar-appearing traits or disorders (such as shyness, sensation-seeking, sensory processing disorder, and autism), and further, that SPS may be a basic variable that may underlie multiple other trait differences (such as introversion versus extraversion).

Within humans and other species, two subpopulations of individuals persistently coexist and consistently display different levels of responsiveness to environmental stimuli; the subpopulations respectively embody "responsive" and "unresponsive" strategies that each have corresponding evolutionary costs and benefits. This observation parallels Aron's assertion that high SPS is not a disorder, but rather a personality trait with attendant advantages and disadvantages.

By 2015 the trait had been documented at various levels of study, including temperament and behavior (personality psychology), brain function and neuronal sensitization, and genetics. For example, genetic studies provide evidence that higher levels of SPS are linked to the serotonin transporter 5-HTTLPR short/short genotype, polymorphisms in dopamine neurotransmitter genes, and the ADRA2b norepinephrine-related gene variant.

HSP Scale score patterns in adults were found to be distributed as a categorical variable with a break point between 10% and 35%, with Aron choosing a cut-off of the highest-scoring 20% of individuals to define the HSP category.

Witzelsucht (from the German "witzeln", meaning to joke or wisecrack, and "sucht", meaning addiction or yearning) is a set of rare neurological symptoms characterized by a tendency to make puns, or tell inappropriate jokes or pointless stories in socially inappropriate situations. A less common symptom is hypersexuality, the tendency to make sexual comments at inappropriate times or situations. Patients do not understand that their behavior is abnormal, therefore are nonresponsive to others' reactions. This disorder is most commonly seen in patients with frontal lobe damage, particularly right frontal lobe tumors or trauma. The disorder remains named in accordance with its reviewed definition by German neurologist Hermann Oppenheim; its first description as the less focused "Moria" ("stupidity"), by German neurologist Moritz Jastrowitz, was in 1888.

Due to similarity of symptoms of the disorder to the mannerisms of Batman's arch-rival Joker, it is sometimes known as 'The Joker Syndrome'

Serotonin and norepinephrine reuptake inhibitor, venlafaxine, were given to case study KS four months after initial stroke that started symptoms of witzelsucht. Changes back to his original behavior were noticeable after daily dose of 37.5 mg of venlafaxine for two weeks. In subsequent two months, inappropriate jokes and hypersexual behavior were rarely noticed. Due to the rareness of this disorder, not much research into potential treatments has been conducted.

Although the brain and spinal cord are surrounded by tough membranes, enclosed in the bones of the skull and spinal vertebrae, and chemically isolated by the blood–brain barrier, they are very susceptible if compromised. Nerves tend to lie deep under the skin but can still become exposed to damage. Individual neurons, and the neural networks and nerves into which they form, are susceptible to electrochemical and structural disruption. Neuroregeneration may occur in the peripheral nervous system and thus overcome or work around injuries to some extent, but it is thought to be rare in the brain and spinal cord.

The specific causes of neurological problems vary, but can include genetic disorders, congenital abnormalities or disorders, infections, lifestyle or environmental health problems including malnutrition, and brain injury, spinal cord injury or nerve injury. The problem may start in another body system that interacts with the nervous system. For example, cerebrovascular disorders involve brain injury due to problems with the blood vessels (cardiovascular system) supplying the brain; autoimmune disorders involve damage caused by the body's own immune system; lysosomal storage diseases such as Niemann-Pick disease can lead to neurological deterioration. The National Institutes of Health recommend considering the evaluation of an underlying celiac disease in people with unexplained neurological symptoms, particularly peripheral neuropathy or ataxia.

In a substantial minority of cases of neurological symptoms, no neural cause can be identified using current testing procedures, and such "idiopathic" conditions can invite different theories about what is occurring.

Causes of dizziness related to the ear are often characterized by vertigo (spinning) and nausea. Nystagmus (flickering of the eye, related to the Vestibulo-ocular reflex [VOR]) is often seen in patients with an acute peripheral cause of dizziness.

- Benign Paroxysmal Positional Vertigo (BPPV) – The most common cause of vertigo. It is typically described as a brief, intense sensation of spinning that occurs when there are changes in the position of the head with respect to gravity. An individual may experience BPPV when rolling over to the left or right, upon getting out of bed in the morning, or when looking up for an object on a high shelf. The cause of BPPV is the presence of normal but misplaced calcium crystals called otoconia, which are normally found in the utricle and saccule (the otolith organs) and are used to sense movement. If they fall from the utricle and become loose in the semicircular canals, they can distort the sense of movement and cause a mismatch between actual head movement and the information sent to the brain by the inner ear, causing a spinning sensation.

- Labyrinthitis - An inner ear infection or inflammation causing both dizziness (vertigo) and hearing loss.

- Vestibular neuronitis - an infection of the vestibular nerve, generally viral, causing vertigo

- Cochlear Neuronitis – an infection of the Cochlear nerve, generally viral, causing sudden deafness but no vertigo

- Trauma – Injury to the skull may cause either a fracture or a concussion to the organ of balance. In either case an acute head injury will often result in dizziness and a sudden loss of vestibular function.

- Surgical trauma to the lateral semicircular canal (LSC) is a rare complication which does not always result in cochlear damage. Vestibular symptoms are pronounced. Dizziness and instability usually persist for several months and sometimes for a year or more.

- Ménière's disease - an inner ear fluid balance disorder that causes lasting episodes of vertigo, fluctuating hearing loss, tinnitus (a ringing or roaring in the ears), and the sensation of fullness in the ear. The cause of Ménière's disease is unknown.

- Perilymph fistula – a leakage of inner ear fluid from the inner ear. It can occur after head injury, surgery, physical exertion or without a known cause.

- Superior canal dehiscence syndrome – a balance and hearing disorder caused by a gap in the temporal bone, leading to the dysfunction of the superior canal.

- Bilateral vestibulopathy – a condition involving loss of inner ear balance function in both ears. This may be caused by certain antibiotics, anti-cancer, and other drugs or by chemicals such as solvents, heavy metals, etc., which are ototoxic; or by diseases such as syphilis or autoimmune disease; or other causes. In addition, the function of the semicircular canal can be temporarily affected by a number of medications or combinations of medications.

A neurological disorder is any disorder of the nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord or other nerves can result in a range of symptoms. Examples of symptoms include paralysis, muscle weakness, poor coordination, loss of sensation, seizures, confusion, pain and altered levels of consciousness. There are many recognized neurological disorders, some relatively common, but many rare. They may be assessed by neurological examination, and studied and treated within the specialities of neurology and clinical neuropsychology.

Interventions for neurological disorders include preventative measures, lifestyle changes, physiotherapy or other therapy, neurorehabilitation, pain management, medication, or operations performed by neurosurgeons. The World Health Organization estimated in 2006 that neurological disorders and their sequelae (direct consequences) affect as many as one billion people worldwide, and identified health inequalities and social stigma/discrimination as major factors contributing to the associated disability and suffering.

Many types of sense loss occur due to a dysfunctional sensation process, whether it be ineffective receptors, nerve damage, or cerebral impairment. Unlike agnosia, these impairments are due to damages prior to the perception process.