High-Incidence Disabilities

Specific Learning Disability

A specific learning disability is defined by the IDEA as "a disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, that nay manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or do mathematical calculations."  SLDs encompass a variety of commonly occurring disabilities, including dyslexia (SLD in reading), dyscalculia (SLD in math), and dysgraphia (SLD in writing).  It has been estimated that SLD diagnoses account for nearly half of children receiving special education. See here for more information on SLD.

Speech or Language Impairment

Speech impairment is defined as a communication disorder that adversely affects the ability to talk, understand, read, and write.  The major types of speech impairments are articulation disorders, fluency disorders, and voice disorders.  Language impairments fall into five categories: phonological disorders (difficulty with pronunciation and articulation), morphological disorders (difficulty with word inflection), semantic disorders (poor vocabulary and difficulty with word meaning), syntactical deficits (difficulty with word order and grammar), and pragmatic difficulties (difficulty using language appropriately in different social contexts).  It is estimated that 20% of children receiving special education have a speech or language impairment. See here for more information on speech and language impairment.

Other Health Impairment ("OHI")

OHI includes those disabilities that do not fall into other categories defined by the IDEA and includes disabilities that limit a child's strength, energy, or alertness and adversely affect a child's educational performance.  The most common OHI are ADHD and asthma.  It is estimated that 7.5% of children receiving special education are diagnosed with OHI. See here for an overview of OHI.

Mild to Moderate Intellectual Disability

Intellectual Disability (formerly "mental retardation") is a disability involving limited intellectual functioning and adaptive functioning that begins in childhood.  Students diagnosed with ID have an IQ around 70-75 combined with difficulties with conceptual, social, and practical adaptive functioning.  A low IQ is not sufficient for a diagnosis of ID - the student must also demonstrate a deficit in the ability to engage in daily life skills such as communication and independent living. Mild ID is characterized by an IQ of 50-55 to 70-75 and only limited need for assistance in daily functioning.  Moderate ID is characterized by an IQ between 30-40 and 50-55 combined with intermittent but extensive need for support and assistance.  Severe and Profound ID are much less common.  See here for more discussion of Intellectual Disability. 

Emotional Disturbance 

Emotional disturbance is a chronic inability to maintain satisfactory interpersonal relationships, inappropriate behavior and feelings given the circumstances, a pervasive mood of unhappiness or depression, and a tendency to develop physical symptoms or fees associated with school or personal problems that affect a child's educational performance.  ED therefore can include major depressive disorder, schizophrenia, severe anxiety, obsessive-compulsive disorder, and a variety of other mental health disorders. ED can manifest as behavioral problems, and as a result is important to be aware of the emotional diagnoses of students who have a pattern of disciplinary infractions. See here for more information about diagnoses of Emotional Disturbance in schools and here for data involving the overlap of behavioral issues and emotional disturbance.

Low-Incidence Disabilities

Autism Spectrum Disorder ("ASD")

Autism Spectrum Disorder is defined by the IDEA as "a developmental disability significantly affecting verbal and nonverbal communication and social interaction." A student is not considered ASD under the IDEA if she has a primary diagnosis of emotional disturbance. Although ASD is one of the most well-publicized disabilities, it is considered a low incidence disability.  Approximately 12% of students receiving special education have a diagnosis of ASD. See more about autism here and here.

Hearing Impairment and Deafness

The IDEA defines "hearing impairment" as "an impairment in hearing, whether permanent or fluctuating, that adversely affects a child's educational performance" and "deafness" as "a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification." The incidences of hearing loss and deafness is quite low, accounting for approximately 1.3% of students identified with a disability. See here for an overview of hearing loss and deafness.

Visual Impairment (including Blindness)

A visual impairment is any impairment of the ability to see that, even with correction, affects a student's ability to access their education. This disability category includes partial sight and blindness. The incidence of visual impairment is unclear but it is considered a low incidence disability. See here for more information.

Multiple Disabilities

Students with multiple disabilities are those that have more than one disability (such as intellectual disability-blindness, intellectual disability-orthopedic impairment, etc.) covered by the IDEA,  the combination of which "causes such severe educational problems that they cannot be accommodated in special education programs solely for one of the impairments."  Students with multiple disabilities typically have overlapping needs that result in deficits in intellectual functioning, adaptive skills, motor skills, sensory function, and communication skills. The incidence of multiple disabilities is approximately 2% of students receiving special education.  See here for more information on multiple disabilities.

Orthopedic Impairments

Orthopedic impairment are severe physical impairments.  They include congenital anomaly, impairments caused by diseases, and impairment caused by things like cerebral palsy, amputations, or injury.  Students with orthopedic impairment may, but do not necessarily, use orthopedic devices such as wheelchairs or braces. Approximately 1% of students receiving special education have an orthopedic impairment. See here for more information on orthopedic impairment.

Traumatic Brain Injury

Traumatic brain injury is an injury to the brain caused by an external force that results in total or partial functional disability or psych-social impairment. An IDEA-covered diagnosis of TBI requires a head injury resulting in an impairment of a variety of skills, including language, cognition, memory, attention, information processing, physical functions, behavior, information processing, and speech. Although TBI is considered a low incidence disability, it is important to be aware of it because it is frequently diagnosed as a result of an injury and can manifest in a wide variety of ways. See here for more information about TBI and IEPs.