Autism Spectrum Disorder, or ASD, is the term we usually hear when we read about autism.  As the term “spectrum” implies, there are degrees to which individuals are affected by autism, and the term ASD is used to encompass a range of severity of symptoms.  Two children may share the same diagnosis, but they may exhibit different degrees of behavioral symptoms.

How does Autism Affect Children?

Most useful for parents, though, is not so much what terminology is used to describe autism, but rather how the disorder manifests itself and affects those who have this complex neuro-biological impairment.  As the Autism Society of America reports, “Both children and adults with autism typically show difficulties in verbal and non-verbal communication, social interactions, and leisure or play activities.”

Children on the autism spectrum have difficulty interacting with or playing with others.  These difficulties include avoiding eye contact or being averse to being held or touched.  Delays in development of physical, cognitive, social and emotional skills and language acquisition and use (or the achievement and then loss of developmental skills) are also hallmarks of autism.

What Causes Autism?

Although research is ongoing, there is currently no consensus as to the cause of autism.  Genetics and environmental factors may play a role in the development of the disorder, but research has not established any definitive links.

There has been much speculation about whether thimerosal (mercury)-containing vaccines can cause autism.  No research has found a link between vaccines and autism, and nearly all vaccines have been thimerosal-free since 2001.  Researchers do know that parenting styles are not a factor in whether a child is affected by autism.

References and Additional Resources:

The findings of this study, conducted by researchers at the University of California, San Diego (UCSD) School of Medicine and Children’s Hospital and Health Center, is meaningful in terms of earlier diagnosis that can lead to earlier intervention and therefore to improved outcomes for children diagnosed with autism.

Autism is usually diagnosed by age 3; diagnosis is made base on observation of behavior, not a medical test. The earlier the diagnosis is made, the earlier treatment can begin.  The early warning sign of increased brain growth occurs before behavioral symptoms of autism are noted.

Researchers in the UCSD study found that the rapid brain growth in children with autism means that “when the brain is experiencing the world and deciding how to construct itself, it’s growing too fast in the infant with autism,” according to the study’s senior author Eric Courchesne, Ph.D. In short, the brain cannot keep up with experiences and information and this makes “it very hard for autistic children to make sense of the world they live in,“ says Courchesne.

The more excessive the brain growth, the more severe autism is, according to study results.

Researchers studied medical records of 48 children aged 2 to 5 who have an autism diagnosis; head circumferences were compared to the Centers for Disease Control and Prevention’s growth charts for normal development.  The findings were that, on average, the head circumference of autistic children at birth was smaller than about 75 percent of other newborns.  However, in the first year, these children had a rapid growth in brain size, reaching the 85th percentile (only 15 % of other newborns had a smaller head size) at around 1 year to 14 months old.  Then, brain growth slowed.

Courchesne explains:  “This burst of overgrowth takes place in a brief period of time, between about two months and six to 14 months of age. So, we know it cannot be caused by events that occur later, such as vaccinations for mumps, measles and rubella or exposure to toxins during childhood.”

This study, according to Courchesne, “provides, for the first time, a developmental process to target for animal model studies of the disorder. Animal models that accurately mimic these abnormal growth events will be necessary in order to discover causes and biological treatments for autism. Once we know what causes this specific growth defect, it may be possible to use biological treatments to successfully intervene before the overgrowth begins, thereby allowing the brain and behavior to develop down more normal paths.”

While certain other conditions such as hydrocephalus or certain metabolic disorders can cause a large head circumference, they are much less common than autism.

Research has found that experience-guided growth is beneficial to human brain development.  Experiences that pass through certain pathways in the brain lead to higher order neurobehavioral functions and skills, such as motor skills, linguistic, emotional, and cognitive skills.

The findings of this study have positive implications for treatment. Courchesne states, “Using our findings as an early indicator of autism, intervention might begin two or three years earlier when the brain might be at a more malleable stage and so, might result in a better outcome for the child.”

While all it takes to measure head circumference and, consequently, brain size, is a tape measure, not all pediatricians include this in routine visits.  The research team advocates routine head circumference measures in the first year of life.

In 2007, the results of the largest-ever genome scan were published.  Performed by over 120 scientists working in more than 50 research institutions that comprise the Autism Genome Project, the research began in 2002 as a collaboration to identify genes that may cause autism.

Funded by Autism Speaks, the research team used looked for genetic similarities in the DNA from nearly 1,200 families.  Findings of the study included the discovery that neurexin 1, part of a family of genes previously linked to autism, and a gene on chromosome 11 may be linked to autism.

In addition, researchers believe there may be as many as 30 genes involved in autism.  In short, if a child has one or more of these identified genes, then he or she has a higher risk of being born with autism.

Clearly, ongoing research is necessary in order for researchers to get closer to pinpointing a particular gene or genes that are implicated in autism. The next phase of the Autism Genome Project will continue to try to isolate genes that cause autism. The earlier autism is diagnosed, the earlier treatment and intervention can begin; early treatment is imperative in helping children with autism diagnoses to lead more fulfilling lives.  Finding causes of autism is a positive step toward early diagnosis.

References and Additional Resources

Read the National Institute of Mental Healh’s press release here.

Visit the Austism Genome Project’s website here.

While there are no known causes of autism, research into causation is ongoing.  One such causal connection being explored is a genetic cause of autism.

A study at the David Geffen School of Medicine at UCLA has uncovered genetic connections between autism and speech delays.  Funded by the National Institute of Mental Health, National Institute of Neurological Disease and Stroke, Cure Autism Now Foundation and UCLA Center for Autism Research and Treatment, the study was lead by Dr. Daniel Geschwind; the findings of the study were published in The American Journal of Human Genetics’ January 10, 2008, online edition.

This study follows an earlier one of DNA samples from families with an autistic child; that study revealed that autism was connected to a specific region of Chromosome 7 (called 7q35).  In the next study, researchers studied genes from DNA samples from 172 families.  The region’s implication in autism was confirmed by a subsequent study.

A key finding, according to Dr. Geschwind, is that the gene the research isolated, called contactin-associated protein-like 2 (CNTNAP2), “not only may predispose children to autism, [but . . .] also may influence the development of brain structures involved in language, providing a tangible link between genes, the brain and behavior.”

Postdoctoral fellow Brett Abrahams, who led part of the research, states that the research discovered that “CNTNAP2 concentrated in the brain’s structures that are involved in higher cognition gives us strong clues about how its disruption might adversely shape brain development, including speech and language”

Another finding was statistical evidence that the gene is strongest in families with autistic boys than in those with girls or with boys and girls.

Further effects of the study may be discoveries about whether CNTNAP2 has a role in language development in normally developing children.

While research into the causes of autism is ongoing and no one cause has been found, research such as this brings us closer to an understanding of this complex disorder.

References and Additional Resources:

Read more about the study from the National Institutes of Heath here and from the UCLA newsroom here.

A study released in April, 2009, has found that there is a gene variant common among 20 percent of children with autism and that may have a role in 12 to 18 percent of autism cases.  The DNA was found in the fontal cortex, the region of the brain where language and communication is housed.

While there is no cure for autism, there are effective treatments and interventions.  The results of this new study may impact successful treatments. Gerard Schellenberg, a professor at the University of Pennsylvania School of Medicine, the study’s author, states that “When we think about treatments, those target molecules and you have to know what to target. This is a major jump in terms of knowing what we need to look at.”

The molecules on the variant gene help to shape the developing brain’s structure, and the gene variant this study found acts as a link between the brain’s wiring and the child’s development.  Found on chromosome 5, the gene variant occurs in normally developing children as well.  Researchers think that there may be other high-risk variants at work in autistic children.

A second study by a research group led by Hakon Hakonarson from the Center for Applied Genetics at the Children’s Hospital of Philadelphia, replicated the results of the first study and examined the link between genes that help eliminate connections between nerve cells.  The results of the study underscore the theory that abnormal connections between nerves in the brain cause autism.

“Both studies implicated genes involved in synaptic generation and neuronal connectivity,” Hakonarson said. “This is highly consistent with previously published research.”

Hakonarson also posits that environmental factors have a role in autism.

Recently, the National Institutes of Health has made autism a priority research topic and has pledged $60 million to research into the differences within the range of autism spectrum disorders.  Research will focus on developing screening tools, assessing risks, and adapting existing interventions to best help treat children with an autism diagnosis.

These findings challenge a study that previously held that brain abnormalities in autistic children resulted from their brain’s faster development.

The technique used in this study measured the water properties of brain tissue.  In the normally developing brain, water is incorporated into neurons rapidly for the first 6 months of life, and then slows for the next 18 months. The University of Washington study found that, in the autistic brain, water was more mobile.  This finding suggests a delay in the development of neurons, specifically at the grey matter at the brain’s surface.

Dager suggests delays could be caused by inflammation: “If you’ve got inflammation, it can affect connectivity at a critical stage of brain development.” This inflammation during the first year of life could lead to learning problems. “For example,” Dager states, “a child has certain key developmental stages for learning language and if you miss those it can be harder to learn that language.”

This early inflammation, Dager suggest, may be due to a particular gene.  Research into genetic links to autism is ongoing, but Matthew Belmonte, senior research associate at the Autism Research Center at the University of Cambridge asserts that “Until we know exactly what it is that causes the abnormal development of grey matter we cannot develop drug treatments.” Belmonte suggests that “One might look at genes that cause a susceptibility to inflammation instead [of brain changes].”

Whatever the focus of the research, learning more about the causes of this complex disorder can only help researchers to develop more, and more effective, treatment and intervention possibilities.

Dr. Martin Myers, director of the National Network for Immunization Information and a pediatrics professor at the University of Texas at Galveston, explains that “This myth was originally created by a couple of mothers of autistic children who read about methyl mercury poisoning and thought it sounded like autism.”

Methyl mercury is different from ethyl mercury, or thimerosal, which, until 2002, had been used to preserve vaccines.  Today, the only common immunizations that contain thimerosal are Fluzone and Fluvirin, which also come in versions without thimerosal.

Thimerosal has been replaced by alternative preservatives; single-dose vaccines are also used, eliminating the need for preservatives.  One version of the diphtheria-pertussis-tetanus (DPT) vaccine has a trace of thimerosal.

Although myths to the contrary persist, no evidence has been found that links ethyl mercury in vaccines to autism.

Research conducted by the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health in Baltimore shows that thimerosal is excreted from children’s bodies far faster than is methyl mercury.  Dr. Neal Halsey, director of the Institute, states that the investigation of thimerosal in vaccines in 1990s came about not because of a concern about autism, but the concern that, “if by chance children got multiple thimerosal-containing vaccines, they might have enough mercury exposure that it might exceed the EPA guidelines.”

Dr. Halsey explains that the association between vaccines and autism, while incorrect, is understandable because symptoms may begin around the time of vaccinations.

Halsey states that organizations such as Autism Speaks are “not explaining that there will be coincidental timing of people recognizing the early signs of autism at the same time vaccines are given, so it’s an impossible task to try to keep doing research that addresses concerns that parents raise about bad things that are temporally associated with autism.”

The bottom line is that, while methyl mercury (such as that found in some fish and in now-recalled antiseptics Mercurochrome and Merthiolate) may cause problems in children in high doses, there is no causal connection between vaccines and autism.

For more information, see this article from the Pittsburgh Post-Gazette. Find mercury content of vaccines here.

Autistic Disorder

What most people think of when they think of autism is termed autistic disorder.  This disorder is characterized by social and communication challenges, unusual behaviors and interests, and significant delays in language acquisition and usage. Many people who have autistic disorder also have an intellectual disability.

Asperger Syndrome

Asperger syndrome is usually thought of as mild autism. People with Asperger syndrome usually do not have language problems or an intellectual disability.  They may, however, have social challenges, unusual interests, or unusual behaviors.

Rett Syndrome

Rett Syndrome is a neurodevelopmental disorder caused by mutations in a gene, causing genes not to produce proteins.  Children with Rett Syndrome have problems with speech, hand use, and normal movement.  Symptoms of autism such social and language impairments, as well as regression of behavioral milestones, are often seen in girls with Rett Syndrome.
Childhood disintegrative disorder

Childhood disintegrative disorder is often confused with late-onset autism because children with this condition develop normally until age 3 or 4, then exhibit a dramatic loss of communication, social, play, and motor skills.

Autism, however, typically occurs earlier than childhood disintegrative disorder. The loss of skills in those affected by childhood disintegrative disorder is also more dramatic.  This condition is far less common than “classic” autism.

The severity of symptoms for any one individual with an ASD can range from mild to severe, but all disorders share the common symptom of social and communication difficulties.

Causes

Autism is complex, and no one single cause has been identified.  Genetics may play a role, and siblings of autistic children are at a higher risk for developing autism than those with no family history.  Research indicates that some variations in gene development may play a role in the development of autism, as may environmental exposure to certain chemicals and toxins.  Routine vaccinations have been ruled out as a cause for autism. Even  researchers who study autism exclusively can not, as of  yet, point to a specific cause of this disorder.

Symptoms

Because children with autism can be very withdrawn and non-communicative, autism can be bewildering for parents and families of those affected. Children affected by autism share many similar symptoms, such as problems with communication, social interaction, and language use. However, since the range of symptoms is great, one child with autism may function in a way that is more “normal” than another with the same diagnosis.

Diagnosis

Parents are often the first to recognize that something is not right with the development of a child who is ultimately diagnosed with autism.  Diagnosis of autism is based on observation, followed by screening and evaluation. Parents may be relieved to receive a diagnosis since that can then lead to treatment and intervention.  Unlike other disorders or diseases, no one medical test can effectively diagnose or rule out autism.  The process of diagnosis can be a difficult time for parents who are anxious for answers.

Treatment

Autism, based on what is known today, cannot be cured, but treatments and interventions – particularly when they are early and intense – can significantly affect the development of a child with autism. With no “one size fits most” treatment proven effective, parents must remain keenly aware of the symptoms their child exhibits in order to determine what may be effective in their child’s specific case.  Behavioral and speech therapies are being studied and found to be effective at lessening autism symptoms.  Medications and diet are also being studied as potential ways to decrease symptoms, but all of these interventions depend on the child affected, adding to the mysterious nature of autism and its treatment.

Autism is complex, but research has made great strides in determining causes and treatments.  The disorder remains vexing, but continuing research will eventually lead to an increased knowledge of causes and prevention, treatments and interventions.

Autism is not a contagious disorder, nor is it caused by parenting techniques, but it does seem to run in families.  For instance, identical twins are very likely to share an autism diagnosis, and fraternal twins are more likely than other relatives to share a diagnosis.

Some common risk factors for autism are low birth weight and premature birth; advanced parental age; and spontaneous genetic mutations whose cause is unknown.  Some researchers believe that, in children with a genetic inclination toward autism, an environmental exposure may trigger symptoms. Recent studies by researchers at John Hopkins University link autism with a mother’s autoimmune disorders such as celiac disease and rheumatoid arthritis.  The Johns Hopkins study concluded that, if one of these disorders is present in the mother, the risk of autism in her child is increased threefold.

Research has not found a causal connection between exposure to mercury used in routine childhood vaccinations and autism, nor is there any clear research connecting children with seizure disorders, bipolar disorder, sensory integration dysfunction, digestive issues, or food allergies and autism, although some of these problems may co-exist in children with autism.

No two children with autism will share identical symptoms; autism is a spectrum disorder, meaning that symptoms vary widely among individuals who are affected by it.  Because of the complexity of the disorder, and the fact that it is diagnosed based on observation of behavior and not on a medical test, isolating risk factors and causes is tricky.  Research into causality continues, and research into new theories is growing.  Until more definitive answers regarding causality can be found, a focus on early diagnosis and appropriate treatment and intervention is imperative in order to effectively treat children with autism diagnoses.

Additional Resources:

Read the US Centers for Disease Control and Prevention’s autism risk factors page here.