What Causes Autism Spectrum Disorders?

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History of Attribution of Cause

Autism has long been considered a classification of a mental disorder. Early individuals with moderate to severe delays in language and social skills would have been placed in institutions to be “treated” by the medical establishment of the time. Kanner, a psychiatrist, first wrote about “infantile autism” and the associated symptoms in his paper in 1943. It is likely that individuals with autism who were high functioning were considered odd, loners who were not classified as needing intervention.

In the 1950s psychiatrist Bruno Bettelheim attributed the symptoms of autism to uncaring and detached mothers who did not love their children enough. Treatment consisted of removing the children from these “refrigerator mothers,” offering psychoanalysis or counseling to the mother, and providing play therapy to the child, ideally in Bettleheim’s institute in Chicago. The disorder was thought to occur in middle-class Caucasian families where both parents were educated. During this period of history not only did the mothers of children with autism have to care for a child with challenging and unusual behaviors, they also experienced the added burden of being blamed as the cause.

In 1964, Bernard Rimland published the book Infantile Autism: The Syndrome and Its Implications for a Neural Theory of Behavior, which attributed the cause of autism to biology rather than poor parenting. Rimland dedicated his career to addressing the biological issues that contribute to and result from autism spectrum disorders. He had long hypothesized that there are brain differences in individuals with ASD compared to the brains of typically developing children. Rimland founded the Autism Research Institute (ARI) that supports the project Defeat Autism Now, or DAN. Annual conferences are held where physicians present information on possible metabolic (interrelated chemical interactions that provide the energy and nutrients) contributions to symptoms and suggest diets that can be used to avoid the side effects of toxins for individuals with ASD.

Genetic Influences.

Autism is currently considered a neurological disorder that is influenced by both environmental (including the in-utero environment) and genetic factors (Sigman, Spence, & Wang, 2006). Evidence for a genetic contribution to ASD is found in a series of twin studies conducted across several countries with similar outcomes (Rutter, 2005). When one twin in a monozygotic pair of twins (identical) was diagnosed with autism, there was a high likelihood that the second twin, with the same DNA, also was diagnosed with autism (Cook, 1998). However, in dizygotic twins (fraternal) the concordance for the diagnosis for autism was very low.

Twenty-eight pairs were examined in the United Kingdom, with 60% of the monozygotic twins both being diagnosed with autism and 0% of the dizygotic twins receiving the diagnosis (Bailey et al., 1995). In Scandanavia, 21 pairs were assessed, with a 91% concordance for monozygotic twins and 0% for dizygotic (Steffenburg et al., 1989). In the United States, 61 pairs were assessed, with a concordance rate of 95.7% for monozygotic twins and 0% for dizygotic (Ritvo, Freeman, Mason-Brothers, Mo, & Ritvo, 1985).

In addition to the twin studies it has been found that the reoccurrence risk for siblings (4.5%) is 45 to 90 times greater than the population risk (.05 – .1%) (Cook, 1998). Results of surveys have revealed that relatives have an increased frequency of lesser variants of autism, including social, language, and repetitive behaviors (Rutter, 2005).

In Their Words Author: Laura Wood

Three Children on the Spectrum

My husband and I have three wonderful sons. They are all on the autism spectrum. Our oldest son Alex’s diagnosis at age 2.5 came as a tremendous blow to us, as it does to every family grappling with this disorder. At that time our twins were 5 months old and we were thoroughly overwhelmed by our responsibilities. But we managed to launch a high-quality home intervention program for Alex and felt that we were doing everything we could do for him.

As the shock of Alex’s diagnosis wore off a bit, I did start overanalyzing certain observations of the twins’ behavior. Were they smiling? Paying attention to faces? During their first year of development, despite my hypervigilance, I believed it to be unlikely that they were autistic. I had not yet heard about the increased likelihood of autism in siblings of autistic children, so I told myself I was being unnecessarily paranoid.

But as the months went by and certain developmental milestones were missed or seemed ambiguous, the nagging feeling returned and slowly I realized that the nightmare scenario was coming to pass. The twins were both diagnosed with autism spectrum disorder shortly before their second birthday.

The most obvious impact of having kids “on the spectrum” is the financial commitment required for their home therapy. We are extremely lucky in Seattle to have a wonderful integrated preschool that all three kids attend for specialized instruction; but supplemental home programs are also recommended for two of our children, and the staggering cost of those programs is not covered by health insurance.

In addition, as many parents of children with special needs will tell you, guilt is ever-present. Sometimes the guilt has a specific source (Am I spending enough time encouraging communication and appropriate play? Have we set up enough hours of home therapy?). Other times the guilt is vague, intangible, and inexplicable.

I have times when I feel bitter and isolated. I look at other families with typically developing children with longing or even with anger. They can’t know what it’s like to take their children to countless therapy appointments and spend tens of thousands of dollars on essential therapy. How can I relate to these parents who take for granted their child’s imaginative play skills or brag recklessly about their baby’s first words? And how can they relate to me when I occasionally confess the reason why my kids don’t always respond appropriately to a peer’s invitation to play? Unless autism has touched their lives in some way, a blank look tinged with pity is all those parents can muster.

But in other ways I recognize the gifts sent our way by this unexpected path in life. There are several wonderful teachers and therapists who would never have been in our lives had it not been for the autism in our family. And my children have reminded me that there are different varieties of intelligence beyond what we think of as typical.

My kids are sweet, wonderful rays of sunshine in my life. They give me so much joy that all the worry and guilt and expense are absolutely worthwhile. I have already learned from them, and I’m sure they have more to teach me as we continue through our lives together.

“Autism spans the genome” (Coleman & Betancur, 2005, p. 17), or is likely to be caused by multiple genes on several chromosomes, and is likely to be associated with chromosomal deletions. Our genes are found on 23 pairs of chromosomes numbered from 1 to 22 and an X or Y chromosome. The larger the number of the chromosome, the smaller the size of the chromosome. When using specialized equipment, each chromosome appears in an X shape with the top arms, or p part, shorter than the lower and longer q portion.

Research indicates that autism spectrum disorder is caused by 2 to 20 susceptible genes across various chromosomes acting in concert (LeCouteur et al., 1996; Minchew, Sweeney, Bauman, & Webb, 2005; Sigman et al., 2006). It is hypothesized that genes on the following chromosomes could contribute to ASD: chromosome 1p, chromosome 2q, chromosome 3, chromosome 5p (Rutter, 2005), chromosome 7q (Buitelaar & Willemsen-Swinkels, 2000; Cook, 2001; Rutter), chromosome 11 that affects the glutamate neurotransmitter system, chromosome 13q (Rutter), chromosome 15q11-q13, or the same region that is missing in Prader-Willi and Angelmann syndrome (Cook; Rutter), chromosome 16 (Rutter), chromosome 17 that has a serotonin transporter gene (Cook), chromosome 19p and 19q (Rutter), chromosome 22q11.2 (Fine et al., 2005), and the X chromosome (Coleman & Betancur, 2005; Rutter). Autism resulting from chromosome 15 is likely due to chromosomal duplication (Coleman & Betancur; Rutter). Chromosome X is of particular interest due to the higher ratio of males to females with the disorder and because of fragile X syndrome, which results in similar symptoms (Coleman & Betancur; Rutter).

It is likely that autism is a syndrome with a common phenotype (visible characteristics) expressed by many different underlying diseases (Coleman & Betancur, 2005). There have been at least 60 different disease entities in individuals that meet the standardized criteria for autism (Coleman & Betancur). There is also mounting evidence that for a significant number of children with ASD, their symptoms may arise from disease of the mitochondria. Mitochondria are rod-shaped bodies found in most cells that produce enzymes for the metabolic conversion of food to energy. Mitochondria cells contain their own DNA that differs from the DNA found in the cell nucleus, and most of the chemical energy in the brain is produced by the mitochondria (Coleman & Betancur).

It is hypothesized that each of the disease entities underlying autistic syndromes will eventually be identified and found to have its own distinctive variation of clinical symptoms and its own specific neuropathology. (Coleman, 2005, p. 63)