Overlap rate of the related conditions
Shinji Ijichi, M.D. & Naomi Ijichi, M.D.
March, 1998
Behavior is one of the most complex and subtle of all human traits. The group of disorders of development with life-long effects (the autistic spectrum, Attention-Deficit/Hyperactivity Disorder, learning disability, etc.) can be
characterized as just a tail of the gaussian distribution of a behavioral parameter. Psychologists and psychiatrists often have trouble even defining and classifying these disorders. Clinical criteria for distinguishing these closely-related conditions tend to be arbitrary, and are sometimes difficult to apply and unhelpful in clinical practice. Many factors (including examiner's bias and behavioral changes in structured situations for assessment) also affect the result of diagnosis. In this page, previously established information on the overlap rate of these related conditions are summarized.
"About 65-88% of autistic individuals are classified as learning disabled" (1)
"14.3% of children with a learning disability fulfilled the diagnostic criteria for autistic disorder (DSM-III-R)" (2)
"Approximately 40% of the adult population with learning disabilities showed the presence of one or more autistic traits" (1)
"It is no surprise that some higher-functioning autistic children chould also be placed in the LD group" (3)
"They (autistic children) may be hyperactive" (4)
"they (autistic children) are virtually incapable of focusing on a joint endeavor with another person" (5)
"Only Pervative Developmental Disorder preempts the diagnosis of Attention-Deficit/Hyperactivity Disorder. Autistic Disorder precludes the use of this diagnosis." (6)
Autism
"Learning Disorders are found in 10% to 20% of individuals diagnosed with Conduct Disorder, Oppositional Defiant Disorder, Attention-Deficit/Hyperactivity Disorder, Major Depressive Disorder, or Dysthymic Disorder" (6)
"(in children diagnosed with Attention-Deficit/Hyperactivity Disorder) symptoms of other disorders, such as conduct and anxiety disorders, increase with age" (7)
"Overall 73% of boys with fragile X syndrome (FXS) fulfilled Attention-Deficit/Hyperactivity Disorder DSM II-R criteria" (8)
"The three larger studies which utilized the rigorous criteria of DSM III or DSM III-R for autism demonstrated a prevalence of 16 to 17% for autism in FXS" (8)
"Overall, approximately 6.5% of males with autism test positive for FXS when subjected to cytogenetic studies" (8)
"Probably less than 5 percent of children with autistic traits have fragile X or any of the other, rarer chromosomal abnormalities." (5)
"a diagnosis of autism presently or in the past occurred in 38.7% of boys with FXS" (8)
"A proportion of patients with dyslexia (12 to 24 percent) will also have attention deficit-hyperactivity disorder" (9)
"(dyslexia) affecting 80 percent of all those identified as learning-disabled" (9)
References
1. Bhaumik S, et al. Autistic traits in adults with learning disabilities. Br J Psychiat 170: 502-506, 1997.
2. Deb S & Prasad KBG. The prevalence of autistic disorder among children with a learning disability. Br J Psychiat 165: 395-399, 1994.
3. In: High-functioning Individuals with Autism. (Eds. Schopler E & Mesibov GB) Current Issues in Autism. Plenum, New York & London, 1992.
4. In: Children with Autism: Diagnosis and Interventions to Meet Their Needs. (Trevarthen C, et al) Jessica Kingsley Publishers, London & Bristrol, 1996.
5. Rapin I. Autism. N Engl J Med 337: 97-104, 1997.
6. In: DSM-IV Training Guide for Diagnosis of Childhood Disorders. (Eds. Rapoport JL & Ismond DR) Brunner/Mazel, New York, 1996.
7. Swanson JM, et al. Attention-deficit hyperactivity disorder and hyperkinetic disorder. Lancet 351: 429-433, 1998.
8. In: Fragile X Syndrome: Diagnosis, Treatment, and Research. (Eds. Hagerman RJ & Cronister A) Second Edition, Johns Hopkins, Baltimore & London, 1996.
9. Shaywitz SE. Dyslexia. N Engl J Med 338: 307-312, 1998.
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