|In This Special Report:|
Autism spectrum disorders (ASDs) are a group of 5 neuro developmental conditions (autism, Asperger syndrome, pervasive developmental disorder not otherwise specified [PDD-NOS], Rett syndrome, and disintegrative childhood disorder).1 Once thought to be rare, the incidence of these disorders is now estimated to be 1 in 150 children in the general population.2 Furthermore, the number of recognized cases has increased markedly in recent years.
Many factors have contributed to the increasing numbers of persons with ASD. These include expanded diagnostic criteria, more diagnostic groups, extended evaluations that range over an entire life span, better and more comprehensive assessment methods, more and better trained professionals, and better funding for research and screening.3 Croen and associates4 found similar rates of developmental disability overall. The rise in ASD diagnoses has paralleled a decline in primary diagnoses of intellectual disability.
ASD does not inoculate persons from the range of psychiatric conditions that affect others in society. We follow the lead of Gilberg and Billstedt5 who describe comorbidities as overlapping disorders. A descriptive definition versus one that implies a direct or indirect link is important, because it is also possible that comorbid disorders occur by chance without an overlapping cause.
Psychiatric disorders are distinct from challenging behaviors that co-occur at high rates with ASD, along with conditions such as intellectual disability and epilepsy. Some forms of psychopathology are particularly common in ASD including atten- tion-deficit/hyperactivity disorder (ADHD), psychosis, depression, anxiety, and obsessive-compulsive disorder (OCD).6,7 Consequently, the clinician needs to:
• Determine whether the patient has ASD. If this diagnosis is made, the type of ASD needs to be pinpointed along with the severity of specific symptoms, as well as the severity of the overall disorder.
• Identify challenging behaviors and determine whether they are environmentally maintained or if they are linked to ASD or co-occurring conditions.8
• Assess whether comorbid intellectual disability is present.
• Consider the possibility of comorbid psychopathology.
While variability in level of overlap in these disorders is debatable, experts agree that overlap is considerable.
The specifics on how to address each of these issues follow, using the best available evidence-based practices. In all instances, the use of a reliable and valid test, clinical observation, school or home observation or report, clinical history, and clinical consensus constitutes the gold standard in inpatient settings.
Developmental factors are in play relative to this spectrum of diagnoses. Rett syndrome, which is quite rare, can be reliably evaluated via genetic testing; it can be identified earlier than other forms of ASD. The severity of symptoms and course in Rett syndrome vary over time. Thus, additional behaviorally based assessments of symptoms should be made over time. Autism (in about half of cases) and disintegrative childhood disorder (in all cases) involve marked loss of previously acquired skills at approximately 18 to 30 months of age. For the remainder of children with autism, diagnosis as young as 18 months may be possible, although some debate exists regarding the exact age cut-off point that will produce a reliable and valid diagnosis.9
Filipek and colleagues10 report on the number of unrecognized cases of autism before school age and the need for more intensive screening efforts. They emphasize that screening is particularly important for children at risk for any type of atypical development. However, regression at approximately age 2 and the heterogeneity of symptoms make this a daunting task.
No consensus exists on how early PDD-NOS or Asperger syndrome can be diagnosed. However, because PDD-NOS has milder symptoms than autism, it may be more difficult to identify in young children. Children with Asperger syndrome have a normal or higher than normal IQ; consequently, this disorder cannot be diagnosed as early as other ASDs.
There has been ongoing debate about whether Asperger syndrome is a separate diagnosis from high-functioning autism (HFA).11 We recommend the use of a scale that is designed to aid in diagnosing suspected Asperger syndrome.12 Thus, for early identification, autism and PDD-NOS will be the disorders screened for by the clinician in most instances. The Table presents scales/tests with established psychometrics that can facilitate diagnosis. Use of at least one of these measures as part of the clinical process is advisable.
1. Starr E, Berument SK, Pickles A, et al. A family genetic study of autism associated with profound mental retardation. J Autism Dev Disord. 2001;31:89-96.
2. Centers for Disease Control and Prevention. Autism Information Center. Published February 9, 2007. http://www.cdc.gov/ncbddd/autism/overview.htm. Accessed August 25, 2008.
3. Matson JL. Current status of differential diagnosis for children with autism spectrum disorders. Res Dev Disabil. 2007;28:109-118.
4. Croen LA, Grether JK, Hoogstrate J, Selvin S. The changing prevalence of autism in California. J Autism Dev Disord. 2002;32:207-215.
5. Gillberg C, Billstedt E. Autism and Asperger syndrome: coexistence with other clinical disorders. Acta Psychiatr Scand. 2000;102:321-330.
6. Helverschou SB, Bakken TL, Martinsen H. The Psychopathology in Autism Checklist (PAC): a pilot study. Res Autism Spectr Disord. 2008. In press.
7. Matson JL, Nebel-Schwalm MS. Comorbid psychopathology with autism spectrum disorder in children: an overview. Res Dev Disabil. 2007;28:341-352.
8. Matson JL, Minshawi NF. Functional assessment of challenging behavior: toward a strategy for applied settings. Res Dev Disabil. 2007;28:353-361.
9. Matson JL, Nebel-Schwalm MS, Matson ML. A review of methodological issues in the differential diagnosis of autism spectrum disorders in children. Res Autism Spectr Disord. 2007;1:38-54.
10. Filipek PA, Accardo PJ, Ashwal S, et al. Practice parameter: screening and diagnosis of autism: report of the Quality Standard Subcommittee of the American Academy of Neurology and the Child Neurology Society. Neurology. 2000;55:468-479.
11. Schopler E, Mesibov GB, Kunce LJ. Asperger
Syndrome or High-Functioning Autism? New York: Springer; 1998.
12. Matson JL, Boisjoli JA. Strategies for assessing Asperger’s Syndrome: a critical review of data methods. Res Autism Spectr Disord. 2008;2:237-248.
13. Rojahn J, Matson JL, Lott D, et al. The Behavior Problems Inventory: an instrument for the assessment of self-injury, stereotyped behaviors, and aggression/destruction in individuals with developmental disabilities. J Autism Dev Disord. 2001;31:577-588.
14. Matson JL. Challenging Behaviors: QABF. Disability Consultants, LLC. www.disabilityconsultants.org/
QABF.htm. Accessed March 16, 2009.
15. Ghaziuddin M, Ghaziuddin N, Greden J. Depression in persons with autism: implications for research and clinical care. J Autism Dev Disord. 2002;32:299- 306.
16. Matson JL, Wilkins J, González ML. Early identification and diagnosis of autism spectrum disorders in young children and infants: how early is too early. Res Autism Spectr Disord. 2008;2:75-84.
17. Fecteau S, Mottron L, Berthiaume C, Burack JA. Developmental changes of autistic symptoms. Autism. 2003;7:255-268.
18. Siklos S, Kerns KA. Assessing diagnostic experiences of a small sample of parents of children with autism spectrum disorders. Res Dev Disabil. 2007;28:9-22.
Matson JL. Current status of differential diagnosis for children with autism spectrum disorders. Res DevDisabil. 2007;28:109-118.
Matson JL, Nebel-Schwalm MS. Comorbid psychopathology with autism spectrum disorders in children: an overview. Res Dev Disabil. 2007;28:341-352.