Causes of Autism Spectrum Disorder

Autism, unfortunately, is a brain disorder of unknown etiology - which means, in practical terms "We don't know what causes it." There are a number of theories, and a lot of controversy surrounding the causes of autism, and some of it is wrapped up in the controversy surrounding just how common autism is, and whether or not there's been a sharp increase in actual cases of autism in the past ten years.

For parents, one of the most important things to know is that autism is NOT a psychological disorder. Researchers have long since put to rest the theory that autism is caused by the lack of a nurturing mother, but the belief still persists in some circles. If your child has been diagnosed with autism, rest assured that it is not because you were a bad parent.

Research into the causes, the diagnosis, and the treatment of autism spectrum disorders has advanced in tandem. With new well-researched standardized diagnostic tools, ASD can be diagnosed at an early age. And with early diagnosis, the treatments found to be beneficial in recent years can be used to help the child with ASD develop to his or her greatest potential.

There's a great deal of research that strongly suggests a genetic basis for autism. For instance, the incidence of autism in the general population is approximately 1.5 in 1000 people, but parents who have one autistic child have a 1 in 20 chance of having another autistic child. In fact, neurobiologists believe that autism is the most heritable of all the neurobiological conditions. The most persuasive evidence is the research done in twins. Twin studies can help establish a genetic link for a condition by examining the difference in prevalence of the condition in identical (monozygotic) and fraternal (dizygotic) twins. If a condition is genetic in origin, the prevalence will be markedly higher in monozygotic twins, since they share the exact same chromosomes. In most twin studies that have been done for autism, the prevalence of autism is as much as 90% higher in monozygotic twins than in dizygotic twins.

On the other hand, the studies raise other questions. The fact that not one of the studies showed 100% concordance in monozygotic twins suggests that there are other factors at play in the causes of autism, for instance. And other familial studies have noted common characteristics - for instance, that autism is more common in families of physicists and engineers, giving rise to the term 'the geek syndrome' to identify autism.

A number of researchers believe that there may be an environmental factor in the development of autism. Dr. Bernard Rimland, for instance, proposed in 1967 that autism may be a result of mercury and heavy metal toxicity to which some children have a genetic sensitivity. His treatment of autistic children with a gluten-free, casein-free diet and mercury chelation therapy (removal of mercury from the system) has shown some success with some children.

Other environmental factors that have been suggested to play a part are viral or bacterial infections, vaccines and thalidomide.

Autism Talk

I have started a brief discussion about autism on my other blog recently. Then I thought it might be better if I made another one dedicated only to talk about autism... Autism Talk! Yup, at least we will have more spaces than just a label :-P.

So, let's just get started. As my first post, I will talk about "What Is Autism?"

Autism is a chronic brain disorder characterized by difficulty with social interaction, verbal skills and communication, repetitive and narrow interests, and often violent reactions to changes in the environment. There is no known cause, though some scientists and researchers suspect a genetic abnormality, injury to the brain or exposure to an environmental toxin.

Autism is most often diagnosed in early childhood, between the ages of 12 and 36 months. That's when most parents begin to notice that their child is not developing speech and communication skills normally, or that they may have disturbed social interactions. Children with milder forms of the disorder may not be diagnosed until they begin school, and for some, even later, at the beginning of middle school, when social and communication skills become more important.

Autism is a commonly used term to describe any one of five pervasive developmental disorders, collectively known as 'autism spectrum disorders'. There are numerous theories about how the disorders relate to each other (we will discuss more about this later). Some researchers believe that they are separate disorders which have similar symptoms, while others feel that there exists a 'spectrum' of severity that ranges from extremely mild (like many children with Asperger's syndrome) to incapacitating. The five pervasive developmental disorders are autism, Asperger's syndrome, Rett Syndrome, childhood disintegrative disorder (CDD), and pervasive developmental disorder not otherwise specified.

Autism - symptoms appear before age 3, though they may not be diagnosed till much later. Symptoms include difficulty making or maintaining eye contact, disturbances in social functioning and an overwhelming self-absorption.

Asperger's syndrome - like autism, symptoms appear before age 3. Asperger's children and adults are more likely to be higher functioning and capable of independent or supported living. Symptoms include difficulties in social functioning, difficulties in communication and speech, and an absorption in narrowly defined interests. Some children with Asperger's syndrome are savants in some area.

Rett Syndrome - afflicts almost exclusively girls. The child usually develops normally for 6-18 months, then shows a marked loss of skills. Acquired speech is lost, and the child may be unable to control her hands and feet. Rett Syndrome can be tested for with 80% accuracy.

Childhood disintegrative disorder - A child develops normally through 2-4 years, then shows a marked degeneration in social, physical, mental and verbal skills. The long period of normal development marks the difference between autism and CDD.

Pervasive developmental disorder not otherwise specified - is diagnosed when there are impairments in social interaction, stereotyped behavior and communication, but the child doesn't meet the criteria for one of the other four disorders.