News and Notes about Scientific Research on Autism and other Developmental and Behavioral Disorders

Editor: Bill Ahearn, Ph.D., BCBA
Director of Research, The New England Center for Children

No empirical support for the “gut theory” of autism
October 28, 2002

Autism encompasses a spectrum of developmental disorders and there is very strong empirical evidence that this spectrum of disorders has a genetic origin with at least three chromosomes identified as having a likely link to autism (IMGSAC, 2001). However, Wakefield and his colleagues have suggested an association between chronic gastrointestinal difficulties and autism and suggested that autism and bowel problems were triggered by the MMR vaccine. This work was somewhat suspect in the soundness of the methods used and prompted a number of researchers to investigate these claims.

Fombonne and Chakrabarti (2001) did an extensive survey of the potential relation between autism and the MMR vaccine and found that there was no evidence for a relationship between the vaccine and autism. Brent Taylor and his colleagues (2002) in a study with nearly 500 children with an autistic spectrum disorder (ASD) and found no relationship between the MMR vaccine and bowel problems. In addition, Black, Kaye and Jick (2002) published a study comparing the prevalence of GI disorders in children with an ASD to typically developing children. They found that children with ASD were no more likely to have a GI problem than there age matched peers. These studies strongly indicate that there is no link between the gut and autism.

The gut theory of autism has produced much interest in dietary treatment for autism. For children who have documented food allergies or intolerance, dietary restriction as directed by a competent physician can be quite important. On the other hand, dietary restrictions or fad diets used as treatment for ASD have not been supported by sound research. The benefits of these approaches are unproven (see NYSDHEIP, 1999 for a summary) and given the restrictions these diets place upon the foods presented to the child, dietary restriction can lead to the worsening of poor eating or directly produce problematic feeding.

Black, C., Kaye, J., & Jick, H. (2002). Relation of childhood GI disorders to autism: Nested case-control study using data from the UK General Practice Research Database. British Medical Journal, 325, 429-421.

Fombonne, E. & Chakrabarti, S. (2001. No evidence for a new variant of measles-mumps-rubella-induced autism. Pediatrics, 108, E58.

International Molecular Genetic Study of Autism Consortium (2001). A genomewide screen for autism: Strong evidence for linkage to chromosomes 2q, 7q, and 16p. American Journal of Human Genetics, 69, 570-581.

New York State Department of Health Early Intervention Program. (1999). Clinical Practice Guideline: Report of the Recommendations. Autism/Pervasive Developmental Disorders, Assessment and Intervention for Young Children (Age 0-3 Years) (Publication No. 4215, pp. 163-194). Albany, NY: Author.

Taylor, B. et al. (2002). MMR vaccination and bowel problems or developmental regression in children with autism: Population study. British Medical Journal, 324, 393-396

Is there an increase in the prevalence of autism?

When Kanner published his seminal paper on autism in 1943 the prevalence1 of autism was estimated to be at 2-4 per 10,000 children. Recent studies have estimated the prevalence of autism as being as high as 60 per 10,000 children. Many in the autism community feel that there has been a rise in the prevalence of autism. However, a thorough review of the prevalence of autism recently published by Lorna Wing and colleagues (Wing & Potter, 2002), concludes that this reported rise in prevalence is likely “due to changes in diagnostic criteria and increasing awareness and recognition of autistic spectrum disorders.”

Wing and Potter (2002) reviews all of the published studies of the incidence and prevalence of autism. The survey of these studies suggests that early estimates underestimated prevalence. However, over time diagnostic criteria have been developed and refined as more information about autistic spectrum disorders has become available. Reliable methods for identifying autism have been rather widely disseminated and there is increased public awareness of the disorder. Interestingly, Wing and Potter noted that the estimates in the more recent studies have had widely varying results. They suggest that different groups of researchers interpret diagnostic criteria in a dissimilar manner. Regardless, practically every recent study of prevalence produced estimates of the disorder that are much higher than the original 2-4 per 10,000 children. Wing and Potter note that there is no empirical evidence for an environmental cause of autism (e.g., MMR vaccine, mercury poisoning, inflammatory bowel disease) though whether there is a true increase in the incidence of autism is still an open question.

1 – Editor’s note. The term prevalence refers to the number of individuals in a particular population who are afflicted with the condition being investigated.

Kanner, L. (1943). Autistic disturbances of affective contact. Nervous Child, 2, 217-250.

Wing, L. & Potter, D. (2002). The epidemiology of autistic spectrum disorders: Is the prevalence rising? Mental Retardation and Developmental Disabilities Research Reviews, 8(3), 151-161.

Research at The New England Center

Editor’s note: The following is an abstract of a recent study conducted in NECC’s preschool. Stereotypy is often a challenging behavior to address. It is a behavior that can interfere with learning but is also commonly encountered in persons without developmental disabilities. Many researchers have concluded that stereotypy is a behavior that is most often maintained by the sensory consequences of the stereotypic action (e.g., rocking, hand-flapping, etc.). The preschool research group has also studied stereotypy in typically developing children; we will detail some of this research in a future edition of the newsletter.

Anderson, J., Gardenier, N., Geckeler, A., Holcomb, W., MacDonald, R., Mansfield, R., Green, G. (In preparation). Age at treatment entry and changes in stereotypic behavior in young children with autism.

Many children with autism engage in stereotyped and repetitive behavior. Decreasing stereotypy and increasing alternative or incompatible responses is often a primary goal for intervention. Research has shown that levels of stereotypy in young children with autism vary with age: Children who entered treatment at age 2 had lower levels of stereotypy than children who entered treatment at age 4. This study compared levels of stereotypy in 2-, 3-, and 4-year-olds with autism during structured and free-play activities when they entered treatment and one year later. Results indicated that 2-year-olds had lower levels of stereotypy (mean: 13%; range: 2% - 20%) than 3-year olds (mean: 23%; range: 6% - 36%) and 4-year-olds (mean: 39%; range: 15% - 61%) at the beginning of treatment. After one year of participation in the Preschool/Homebased Intensive Instructional program, levels of stereotypy remained the same for the 2-year-olds (mean 13%; range 2-20% and decreased for the 3-year-olds (mean 13%; range 5%-44%, with the largest decrease occurring in the 4 –year-old group (Mean 24%; range 7%-36%). Implications are that intensive early behavioral intervention may result in greater behavior change when children begin prior to the age of three.

Editor’s note: Preference assessments are a tool used by behavior analysts to determine the things that will serve as effective rewards for a student. The following study attempts to determine how long an assessment must be to identify these rewards.

Graff, R. B., and Ciccone, F. (2002). A post-hoc analysis of multiple-stimulus preference assessment results. Behavioral Interventions, 17, 85-92.

Fifteen individuals with developmental disabilities participated in multiple-stimulus without replacement preference assessments (7 assessment sessions, 7 trials each). Twelve of 15 individuals completed a second set of preference assessments 6 months later. Post-hoc analyses indicated that in 25 of 27 cases, the same most preferred stimulus was identified in the first 3 trials as the full 7 trials. Additionally, 5 sessions of 3 trials each were sufficient to identify the most highly preferred stimulus in 22 of 27 instances.

Editor’s note: This second investigation involving preference assessments explores whether pictures representing items (pectoral assessment) accurately identify rewards. Preference assessments typically involve allowing the student to choose between the actual items (tangible assessment). However, many potential rewards like community trips, going for a walk, visiting a friend or relative are not easily presented as choices. One thing illustrated by this study is how we might determine whether a student would reliably identify rewards given a pectoral representation of the event.

Graff, R. B., & Gibson, L. (In Press). Using pictures to assess reinforcers in individuals with developmental disabilities. Behavior Modification.

Tangible preference assessments were compared with pictorial preference assessments for 4 individuals with developmental disabilities. In the tangible assessment, on each trial 2 stimuli were selected and placed in front of the participant, who approached one. In the pictorial assessment, on each trial 2 line drawings were placed in front of the participant, who pointed to one. For both assessments, the percentage of opportunities each stimulus was approached or touched was calculated, and hierarchies of preferred items were developed. The 2 assessments yielded similar preference hierarchies for 3 of 4 participants. Reinforcer assessments using a simple free operant response confirmed that items identified as highly preferred on tangible and pictorial assessments functioned as reinforcers.

Editor’s note: This study explores some of the mechanics of delivering treatment for eating problems. It was found that introducing only one food item at a time to a child during treatment led to the child independently eating that item more rapidly. On the other hand, when the child was required to eat several different items during a treatment session, the child was more likely to independently eat new foods during subsequent sessions.

Ahearn, W.H. (2002). Effect of two methods of introducing foods during feeding treatment on acceptance of previously rejected items. Behavioral Interventions, 17, 111-127.

The effects of using a single food item (e.g., bread) versus using multiple items (e.g., bread, pasta, and rice) when establishing food acceptance via an escape prevention procedure were investigated with 6 children who presented with food selectivity. Eating was exposed to a differential reinforcement of food acceptance treatment package but food acceptance did not improve. Criterion levels of appropriate eating (>80% acceptance, <20% expulsion, and <20% disruption) were subsequently established with either nonremoval of the spoon or physical guidance for each of the participants. Three of the children were presented with only one food item during acquisition of acceptance. The other children were presented with 3 different food items from the same food group. It was found that acquisition of acceptance was more rapid for the single-item group but that food acceptance was more likely to generalize to previously rejected items for the multi-item group. The implications for clinical intervention are discussed.

Web Resources

For information about autism, visit the National Library of Medicine’s autism site www.nlm.nih.gov/medlineplus/autism.html.

For information about applied behavior analysis in the treatment for autism visit www.behavior.org.

For science-based information on biomedical treatments and theories in autism visit www.autism-biomed.org.

For professionally screened information on health care (including some treatments for autism and other developmental disabilities), visit www.quackwatch.com.




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