What Causes Dyslexia?

Prevalence

It is estimated that at least 2.19 to 20 percent of the entire population suffers from dyslexia, the most prevalent type of learning disability. In regard to numbers of students who are learning disabled, 4.39 percent have been identified as learning disabled of a total of 8.75 percent disabled students being served in our schools (U.S. Dept. of Education, 2002). We estimate at least half of these students would be classified as dyslexic. As a specific type of learning disability, dyslexia falls under Part B of the Individuals with Disabilities Education Act (IDEA) of 1990, P.L. 101-476:

...a disorder in one or more of basic psychological processes involved in using language, spoken or written, which may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or do mathematical calculations. The term includes such conditions as perceptual handicaps, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia. The term does not include children who have learning problems which are primarily the result of visual, hearing, or motor handicaps, of mental retardation, of emotional disturbance, or of environmental, cultural, or economic disadvantage... (USDOE, 2002)

The Individuals with Disabilities Education Act (IDEA) (P.L. 101-476) of 1990 and 1997 (P.L. 105-17) is a reauthorization of the more familiar P.L. 94-142 (1975) federal legislation, which was called the Education of All Handicapped Children Act (EOAHC). IDEA includes 1983 (P.L. 98-199) (provided funds for planning state services for young children with disabilities ages birth to 5 years of age) and 1986 (P.L. 99-457) (required states to provide services for preschool children) amendments to P.L. 94-142 and a USDOE 2003 reauthorization. Essentially, IDEA is a federal law that provides detailed specifications as to how special services will be administered to disabled children. All disabled children are guaranteed a free and appropriate education under this act. The Federal Office of Special Education Programs, directed by the Deputy Assistant Secretary, is responsible for its implementation. A major change in the P.L. 94-142 (USDOE, 1977) legislation involved deletion of the use of the term handicapped,replacing it with the term disabilities. Additionally, IDEA now requires the transition services for students leaving high school be written into a student's individual education plan (IEP). Typically, sections 617 and 618 of the regulations are referred to by professionals when looking at EOAHC (P.L. 94-142), and sections 1417 and 1418 are referenced with IDEA (P.L. 101-476, 1990).

Federal and International Dyslexia Association Descriptions

It is necessary to distinguish the problem of dyslexia from other learning disabilities. Learning disabilities in general can refer to a number of problems including difficulties in reading (dyslexia) and language, math, memory, and nonverbal communication problems. However, in most instances learning disabilities are almost always diagnosed with the use of a reading assessment battery and almost always refer to some type of reading disability or dyslexia (Aaron & Baker, 1991). Many writers use the term learning disability interchangeably with dyslexia, reading disability (RD), severe reading disability (SRD), and severe reading disorder (SRD). There are no firm figures regarding the percentage of individuals experiencing learning disabilities who are identified specifically as dyslexic. However, a majority would indicate at least 50 percent or 2.185 percent out of the total 4.37 percent learning disabled identified in our schools (USDOE, 2002). The USDOE (2002) reports 4.37 percent out of all disabled students as having specific learning disabilities, covering a wide range of LD categories (including reading, math, and language disabilities). We have estimated 2.185 percent of these students to be dyslexic. Of the total 8.75 percent disabled being served, the specific learning disabled comprise the largest category, followed by speech and language impairments (1.66%), mental retardation (.92%), severely emotionally disturbed (.72%), other health impairments (.44%), multiple disabilities (.19%), autism (.12%), hearing impairments, (.11%), orthopedic impairments (.11%), visual problems (.04%), developmental delays (.04%), traumatic brain injury (.02%), and deaf-blindness (< .001%).

Your author's definition of dyslexia is consistent with that of the International Dyslexia Association (IDA) (2003):

International Dyslexia Association (IDA) (2003) Definition:

Dyslexia is a specific learning disability that is neurological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge. (Hennessy, 2003)

In 2000, the IDA published identifying characteristics that focus not just on the deficiencies in reading and other language forms but on observed strengths as well. IDA stated what dyslexia is not, as there are publications and programs that show a lack of understanding of what can be a debilitating learning problem if appropriate interventions are not in place.

Identifying Characteristics of Dyslexia Incorporating IDA (*) Criteria (2000, 2003):

• Dyslexia is a strongly inherited trait. Muter (2003) has reviewed a body of research that shows estimated heritability is moderately high-0.4 to 0.7 with multiple genes implicated because reading is a complex process.
• Dyslexia is a learning disability characterized primarily by reading difficulties at the word level (specifically the phonology of language and fluency) that usually involves expressive and receptive language involvement. Concomitant and subtle comprehension difficulties may exist as well (*).
• Dyslexia is not the result of low intellectual ability. Intelligence is not a factor (*).
• Problems often emerge in spelling, writing, speaking, or listening (*).
• Dyslexia is not a disease; therefore, it has no cure (*)
• Individuals with dyslexia learn differently (*) or require differentiated or more intense instruction to best meet their learning needs.\par
• An unexpected gap exists between learning aptitude or intelligence and achievement in school (*).
• The problem is not behavioral, psychological, motivational, or psychosocial (*).
• It is not a problem of "seeing backward" (*) but may involve the visual system.
• Many individuals with dyslexia are gifted and creative and have talents in areas such as art, athletics, architecture, drama, electronics, engineering, graphics, mechanics, music, or creative writing with strengths seen in visual, spatial, and motor integration (*).
• The language processing difficulties of individuals with dyslexia (*) (primary presenting problem = acquiring reading proficiency commensurate with age and developmental level) distinguish them as a group.
• The individual with dyslexia then experiences difficulties translating language to thought (as in reading and listening) and thought to language (as in writing or speaking) (*).
• Individuals with dyslexia can and do learn how to read and write proficiently with adequate support systems, but remnants of the language problems will be seen in adulthood (e.g., slower reading rates, the need to use a word processor with spell/grammar checks, and so on).
• Successful individuals with dyslexia have developed resilient personalities with the ability to quickly bounce back or recover from stressors, frustrations, and failures due to a personal resolve to persevere in spite of academic/social obstacles.
• Dyslexia results from differences probably in the structure and function (*) of the brain. To best understand the neurological implications of dyslexia, one first has to picture or understand reading at the cortical level of involvement.

Summary of Important IDEA and NCLB Information Impacting Individuals with Dyslexia.  Beginning in 1994, Congress began to focus on addressing the important practice of including students with disabilities within regular classroom programs. Ensuring that all children with disabilities have available to them a free appropriate public education that emphasizes special education and related services designed to meet their unique needs and prepare them for further education, employment, and independent living under The Individuals with Disabilities Education Act (IDEA) (USDOE, 2003a), means access to the same high-quality literacy resources and instructional research-based practices as in "regular education."

IDEA may be cited as the Improving Education Results for Children with Disabilities Act of 2003(USDOE, 2003a) and legislates authorized formula grants to states, and discretionary grants to institutions of higher education and other nonprofit organizations to support research, demonstrations, technical assistance and dissemination, technology and personnel development, and parent training and information centers. These programs are structured to ensure that in addition to quality education programs, the rights of infants, toddlers, children, and youth with disabilities and their families are protected.

How school systems and other professionals diagnose or assess learning disabilities to include dyslexia will be significantly impacted in years to come with changes to Sections 614(b)(6) of this (IDEA) Individuals with Disabilities Education Act (20 U.S.C. 1400-1402):

Sec. 614(b)(6)- Specific Learning Disabilities: In determining whether a child has a specific learning disability (SLD), the district "shall not be required to take into consideration whether the child has a severe discrepancy between achievement and intellectual ability..." In determining whether a child has an SLD, the district "may use a process which determines if a child responds to scientific, research-based intervention." (USDOE, 2003a)