1. Why is the term “Asperger syndrome” no longer in clinical use in the United States?
The American Psychiatric Association publishes the Diagnostic and Statistical Manual (DSM) which is the primary reference manual used by clinicians to provide a formal diagnosis of autism and related disorders. This manual provides clinicians with standard guidelines for diagnosing different psychological disorders.
In 2013, when the fifth edition of this manual was published, experts significantly revised the diagnostic criteria for Asperger syndrome. Autistic disorder, Asperger syndrome and pervasive developmental disorder were no longer separate diseases, but were replaced by an umbrella term, autism spectrum disorder (ASD). Within this broad diagnosis, patients are classified in different levels based on the symptoms and how severe they are.
The main reason for this change was to create a simpler diagnostic criteria and to accommodate for a wide range of symptoms seen among autistic patients. Since these disorders are characterized by a common set of social and emotional behaviors, it was reasoned they could be grouped under a single unifying term.
2. Do you think there is a significant increase in cases of autism?
According to the Center for Disease Control, 1 in 68 children in the U.S. have autism. The prevalence is 1 in 42 for boys and 1 in 189 for girls, a gender ratio of about five boys for every girl. The latest estimates are up 30 percent from the estimates in 2008 (1 in 88) and more than double the rate estimated in 2000 (1 in 150). The rate has been on a steep rise since the 1990s in the U.S. and worldwide.
Increase in autism rates can be largely attributed to many factors such as better diagnostic methods, greater awareness and understanding among pediatricians and the general public, more trained in-school specialists and importantly, changes in diagnostic criteria in the U.S. (see question #1). Also, many studies have shown that older parents have an increased risk of having a child with autism and/or other neurodevelopmental disorders. Autism rates are higher among children whose parents were 40 or older when they were born, which is happening more often.
Even after adjusting for these factors, there still appears to be an increase in cases of autism over the years. While clinicians and researchers are not sure of the exact cause, they unanimously agree that scientific evidence does not support the claim that vaccines could be the source.
3. What are the genetic causes of autism?
There is no single cause of ASD. It is generally believed that ASD is caused by abnormalities in the brain structure and function due to alterations in genetic or environmental factors.
Most of the genetic changes (either at the chromosomal level or as point mutations in the genes) occur simply because of imperfect biological mechanisms that are a part of the production of sperm and egg cells.
For instance, in every sperm or egg cell, about 3 billion letters of genetic code are faithfully copied over many generations of cellular multiplication. This is a highly regulated process and many complex steps of checks and balances have evolved over millions of years of evolution to prevent genetic errors. However, despite rigorous proofreading, certain errors slip past and are the cause of the huge amount of genetic variation observed in humans.
Most genetic variations are benign and do not lead to autism except if they happen to be in the essential region of one of the hundreds of genes implicated in ASD. The exact nature of the symptoms and how severely an individual is affected depends on the mutations they carry. As expected, genetic mutations affecting master regulatory genes, which control the activity of hundreds or thousands of other genes, cause widespread and severe damage.
Learn more about ASD candidate genes.
4. What is the current status of research on preventing autism?
Research has identified a few genetic and environmental risk factors for autism. However, our understanding of how these factors cause autism is still in emerging stages. While heredity plays a role in some cases, a large number of cases arise due to spontaneous mutations in ASD candidate genes.
There are no standard clinical guidelines to prevent autism at this time. Here are a few things one could consider to reduce the chances of having an autistic child:
Good medical care during pregnancy
Pregnant women should take prenatal vitamins and consult with their physicians to take care of any preexisting health conditions (such as hypertension or diabetes), that can lead to pregnancy-related complications, like preterm labor.
Review medications during pregnancy with an experienced medical provider, and make adjustments as necessary
It is important pregnant women avoid self-prescribing medications during pregnancy. Certain medications, such as valproic acid (anti-convulsant also prescribed for migraines and bipolar disorders), certain psychotics and mood stabilizers, terbutaline (to stop premature labor) and thalidomide (anti-cancer drug) have been linked to an increased risk of autism. Hence, a medical professional must be consulted to ensure the medical needs of the mother and baby are balanced with a potential for increased autism risk.
Limit exposure to toxins during pregnancy
Pregnant women should avoid exposure to certain chemicals such as pesticides and phthalates (found in plastics) which have been strongly linked to autism.
Women should consider getting immunized against rubella before they become pregnant to prevent rubella-associated autism.
Plan on having children earlier in life
Increased parental age increases the chances for autism. Some studies have suggested that autism risk is lowest when pregnancies are spaced two to five years apart. Read More
If known ASD mutations run in your families, then you may consider pre-implantation genetic testing. This way, should you choose to do so, you could elect to only implant embryos that do not carry the autism-related mutation(s). This will not account for many ASD genes that we still do not know about, or spontaneous mutations.
Following delivery, early diagnosis and treatment of certain hereditary diseases, such as phenylketonuria (PKU), may reduce the risk of having a child with autism.