What is Autism?
Autism is a pervasive developmental disorder that involves abnormal development and function of the brain. People with autism show decreased social communication skills and restricted or repetitive patterns of behaviors or interests.
By current definition, the onset of autism is prior to age 3 years. When autism was first characterized by Leo Kanner in 1943, the prevalence was estimated at 1 in every 2,000 children. Today, one out of every 68 children is affected with autism or a related disorder. Thus, it is more prevalent than breast cancer or childhood diabetes. The recurrence rate for having a second child with autism if one already exists within a family is thought to be 15-20%.
Based on the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV), autism is currently considered one of five different pervasive developmental disorders that also includes Asperger’s Disorder, Pervasive Developmental Disorder Not-Otherwise Specified (PDD-NOS), Childhood Disintegrative Disorder and Rett’s Syndrome. Childhood Disintegrative Disorder and Rett’s Syndrome are very rare (about 1 in 40,000).
In 2013 the American Psychiatric Association will publish a revised version of the DSM. Current plans for this new version, DSM-V, include only one diagnosis, called autism spectrum disorder or “ASD.” This new diagnostic label will subsume those disorders formerly known as autism, PDD-NOS, Asperger’s Syndrome and Childhood Disintegrative Disorder. Rett’s Syndrome will not be included in the DSM-V.
Twenty years ago the mean age of diagnosis nationally was around age 5. Today many children are being diagnosed near their second or third birthday and in some cases even earlier. The dramatic change in the mean age of diagnosis is due in part to improved diagnostic procedures. The development of the Autism Diagnostic Observation Schedule (ADOS), created by Catherine Lord, Ph.D. and colleagues in the 1980’s has contributed greatly to early diagnosis efforts.
Currently a new diagnostic module, called the “ADOS, Toddler Module,” is available for use with children as young as 12-months old to help the clinician establish a risk profile.
Other early diagnosis efforts are being researched around the country including efforts to develop a diagnostic test for autism based on patterns of functional brain activity, eye tracking or genetic profile, currently ongoing at the UCSD Autism Center of Excellence.
Most but not all children with the disorder experience a sudden increase in brain size around their first birthday. Although a few studies have implicated a relationship between the amount of brain overgrowth and severity of symptoms, there is currently no clear relationship.
Eric Courchesne and his colleagues suggest that the brain undergoes three phases of development: early brain overgrowth followed by arrest of growth and eventually decline. Key brain regions thought to contribute to the symptomology of autism include the:
- Amygdala, which is involved in emotion regulation
- Superior temporal gyrus, which is involved in the development of complex language processing ability
- Frontal lobes, which are involved in higher order cognition including the ability to engage in sophisticated social behavior
Causes of Autism
The causes of autism remain unknown, although the high concordance rate between identical twins, usually 70-90%, confirms that autism is a strongly inherited disorder. Many studies have implicated a variety of developmental genes but none have been found consistently across affected individuals.
Environmental factors, such as exposure to viruses or toxins during pregnancy, are speculated to contribute but none have been conclusively identified.
The clinical description herein will use the term ASD to refer mainly to what is currently known as autistic disorder and Pervasive Developmental Disorder Not-Otherwise Specified (PDD-NOS).
The symptoms of ASD can vary widely. For example, some children may demonstrate extremely poor eye contact, whereas other children with an ASD may demonstrate good eye contact. Some children may not talk at all, whereas other children with ASD may have very good productive language and even be able to converse with others. The dissimilarity of ASD symptoms probably reflects the complexity of brain abnormalities and the underlying genetics that likely involve multiple genes and gene-environment interactions.
Deficits in Social Behavior
In the young child with autism, the epicenter of social deficits are often thought of as abnormalities in “social attention” behaviors. Defects in social attention can take the form of reduced eye contact, reduced showing of objects, reduced pointing, reduced following a speaker’s line of gaze and the like. In brief, the child with autism often does not make frequent attempts to join the social-emotional world of others and, conversely, to draw others into their world.
As the child matures and interpersonal expectations increase, other social abnormalities become apparent, such as more pronounced abnormalities in eye contact, reductions in reciprocal social interaction, and difficulties in identifying and interpreting the emotions of others. Finally, difficulties in the ability to take the mental perspective of another person (a.k.a. “Theory of Mind”) is also common in autism and may emerge as the direct result of difficulties with early social attention.
While the image of an autistic child sitting alone in a corner and swaying his body up and back in a rocking manner is sometimes valid, it does not represent the child as a whole. In fact, children with autism can and do form strong social attachments to their caregivers. They smile and laugh and can experience great joy.
Abnormalities in Language
About half of all individuals with autism fail to develop fully functional speech, and for those who do, language is generally characterized by one or more abnormalities such as pronoun reversal (e.g., saying "he" went to the market instead of "I" went to the market), use of neologisms (nonsensical or made up words), stereotyped or rigid speech, and abnormalities in intonation.
The speech of autistic individuals is also characterized by echolalia, which is the repetition of words either right after someone speaks them or after a delay of hours, days, or even months. For example, an autistic individual may repeat the phrase “how old are you?” hundreds of times in a single day, after hearing the phrase only once. Also, children with low levels of functional speech can often repeat extended sequences heard in their favorite videos or television shows.
Delays in Cognition
In the past researchers and clinicians believed that approximately 75% of people with autism were also cognitively impaired. Today, with improved testing methods and early treatment efforts, more than half of children with autism have cognitive abilities that fall within the normal range, although many still function in the delayed range.
While children with autism may not learn in the same way as typically developing children, current behavioral practices have shown that these children are very capable of learning. In fact, a new study by Geraldine Dawson and colleagues published in 2010 showed that early treatment led to an average 15 point gain in IQ.
Although it is difficult to disentangle secondary effects of early social and language impairment from cognitive deficits per se, some scientists believe that deficits in higher order memory abilities, conceptual reasoning (e.g., categorization skills), executive function (e.g., switching between two or more mental sets), and auditory information processing may be important features of this disorder.
Restricted and Repetitive Interests
Individuals with autism commonly display restricted, repetitive and stereotyped patterns of interests and activities. This general category of behavior manifests itself in many ways such as an inflexible adherence to specific routines, stereotyped and repetitive motor mannerisms (e.g., hand-flapping) or a preoccupation with an object or part of an object.
In general, autistic individuals display a significantly reduced interest in their environment, instead, focusing their attention on one specific aspect of the environment (e.g., a lamp) or obsessive idea (e.g., amassing facts about cars). Further, individuals with autism may insist on sameness and show distress over trivial changes in their environment (e.g., movement of a piece of furniture).
Restricted and repetitive environmental interests likely interfere with learning and may have significant developmental implications for the autistic child because he or she may miss many learning opportunities that fall outside their scope of interest. Combined with attention deficits described above, the autistic child often has difficulty learning from his or her environment.
A wide range of therapies exist to treat the symptoms of autism, most of which are based on a behavioral and/or a developmental model. Commonly used treatments include:
Pivotal Response Training (PRT)
- Floor Time (FT)
- Early Start Denver Model (ESDM)
- Relationship Development Intervention (RDI)
- Discrete Trail Training (DTT)
Therapies based on a “behavioral” model rely on the principles of behavior and attempt to teach child skills by providing specific cues and consequences for behavior in order to teach the child new skills. Therapies based on a “developmental” model focus on identifying a child’s current ability level and guiding him or her through a sequence of learning experiences that become more developmentally complex across time.
While most therapies combine insight from both behavioral and developmental models, some therapies are heavily weighted towards either approach. For example, DTT relies heavily on the principles of behavior whereas ESDM relies heavily on principles of development.
Aside from isolated medications that may be beneficial at targeting specific symptoms such as seizures, there is no medicine or pill to treat autism. Alternative therapies exist such as hyperbaric oxygen or chelation therapy, but there is no scientific evidence to suggest that these therapies are effective. Such alternative therapies also come with some level of safety risk.