There are three main types of ASDs (1):
- Autistic disorder (also called classic autism): Affected individuals often have severe speech, social and behavioral problems. Sometimes individuals also have intellectual disability.
- Asperger syndrome: Affected individuals have milder social and behavioral problems than individuals with autistic disorder. They usually have normal speech and intellectual abilities.
- Pervasive developmental disorder not otherwise specified (also called atypical autism): Affected individuals have some symptoms, often including speech and social problems, but not enough to be diagnosed with classic autism.
The American Academy of Pediatrics (AAP) recommends that all children be screened for ASDs at their regular medical checkups at 18 months and 24 months (2). Early diagnosis and treatment can greatly improve the outlook for children with ASDs.
How common are ASDs?
ASDs may affect about 1 in 110 to 1 in 150 children in the United States (3, 4). This means there may be more than 650,000 children in this country who have some symptoms of autism (4).
More children than ever are being diagnosed with ASDs. The rates of children diagnosed with ASDs have risen dramatically since the 1980s; between 2002 and 2006 they increased 57 percent, from 6.0 to 9.4 cases per 1,000 (3). Much of this increase may be due to improved awareness and changes in how ASDs are diagnosed.
What are the symptoms of ASDs?
Each child with an ASD is unique. Common characteristics and behaviors include a child who (1, 5):
- Does not speak (about 40 percent of children with autistic disorder do not speak at all)
- Repeats words
- Performs repetitive movements, such as hand-flapping
- Doesn’t play “pretend” games
- Is overly active
- Has frequent temper tantrums
- Avoids eye contact
- Has difficulty starting and maintaining conversation and making friends
- Does not respond to being called by name
- Insists on keeping the same routine
- Repeats actions again and again
- Focuses on a single subject or activity
- Wants to be alone
- Is overly sensitive to the way things feel, sound, taste or smell
- Dislikes being held or cuddled
- Has sleep disturbances
- Lacks fear in risky situations
- Has some degree of intellectual disability or learning problems
- Is aggressive
- Hurts himself
- Loses skills (for example, stops saying words he used to say)
When is an ASD diagnosed?
A child with an ASD usually does not look different from other children. He may appear to develop normally for the first year or so of life. But during the second year, some children with an ASD begin to fall behind in social skills, fail to develop speech, or even lose skills that they had previously acquired. An ASD is often diagnosed around age 3; however, subtle signs of the disorder may appear before 18 months (2). These signs may include (2):
- Not turning when the parent says the baby’s name
- A lack of back-and-forth babbling with parents starting around 6 months of age
- Late smiling
- Not looking when a parent points and says, “Look at…”
Toddlers with these signs do not necessarily have an ASD, as each child develops at a different rate. However, parents should discuss these possible signs and other developmental concerns with their baby’s health care provider.
Speech delays can be early signs of ASDs. AAP recommends an immediate evaluation for ASDs if the child (2):
- Does not babble, point or use other gestures by 12 months
- Does not say any single words by 16 months
- Does not say any 2-word phrases by 24 months
- Loses language or social skills at any age
How are ASDs diagnosed?
There is no specific medical test to diagnose ASDs. Health care providers generally diagnose ASDs by observing a child’s behavior. They also use screening tests that measure a number of characteristics and behaviors associated with ASDs. If a screening test suggests a possible problem, the provider may do additional tests or recommend evaluation by a specialist.
Who is at risk of an ASD?
ASDs occur in all racial, social and educational groups. Boys are about 4 times more likely than girls to be affected (1). Siblings of an affected child may be at increased risk of ASDs, though the risk appears fairly low at 2 to 8 percent (1, 2).
Recent studies suggest that premature babies may be at increased risk of symptoms associated with ASDs (6, 7). A premature baby is a baby born before 37 completed weeks of pregnancy. Some of the increased risk is because of the higher rates of problems associated with premature birth (7, 8, 9). These problems include:
- Pregnancy complications, such as preeclampsia, a pregnancy-related form of high blood pressure
- Newborn health problems, such as brain bleeds
- Lasting disabilities, such as cerebral palsy, intellectual disabilities, and vision and hearing impairments
What causes ASDs?
We don’t really understand the causes of ASDs. But scientists do know that autism is not caused by poor parenting or other social factors. It is a biological disorder that appears to be associated with subtle abnormalities in specific structures or functions in the brain.
Genetic and environmental factors appear to play a role in the disorder. Scientists believe that many genes on different chromosomes may be a cause. A research team recently identified a small gene region on chromosome 5 that may be associated with 15 percent of ASD cases (10). Another study found that abnormalities in a small region of chromosome 16 were about 100 times more common in children with ASDs than in unaffected children (11). Certain infections that occur before birth (such as rubella and cytomegalovirus) and older maternal age also have been associated with ASDs (2, 12).
About 10 percent of children with ASDs have other genetic diseases, including (1, 2):
- Fragile X syndrome (intellectual disabilities and behavioral problems)
- Tuberous sclerosis (non-cancerous tumors that affect the brain and other organs)
- Down syndrome and other chromosomal birth defects
Do childhood vaccines contribute to ASDs?
Childhood vaccines, including the measles/mumps/rubella (MMR) vaccine, do not cause ASDs. Many studies have shown no link between the MMR vaccine and ASDs. In fact, the controversial 1998 study that set off concerns about a possible link between the MMR vaccine and ASDs was recently retracted by the medical journal Lancet that originally published it (13).
Some parents of children with autism suspected that the MMR vaccine, given around 12 to 15 months of age, contributed to ASDs because their children began to display symptoms of ASDs around the time they were vaccinated. Most likely, this is the age when symptoms of the disorder commonly begin, even if a child is not vaccinated.
Another reason that childhood vaccines were suspected of playing a role in ASDs is that, until recently, they contained a small amount of a preservative called thimerosal. Thimerosal contains mercury. While higher doses of certain forms of mercury may affect brain development, studies suggest that thimerosal does not. Since 2002, most routine childhood vaccines have not contained thimerosal. Some flu shots contain thimerosal, but parents can request flu shots that are thimerosal-free.
In 2004, an Institute of Medicine panel concluded, after reviewing many studies, that neither the MMR vaccine nor vaccines that contain thimerosal are associated with autism (14). A 2008 study found that the rate of ASDs in California continued to increase after thimerosal was removed from childhood vaccines, also suggesting a lack of association between thimerosal and ASDs (15).
How is autism treated?
Children often show great improvement with intensive behavioral treatment beginning during the preschool years. A recent study of children diagnosed with ASDs between the ages of 18 and 30 months found significant improvements in IQ (nearly 18 points), language skills and behavior after 2 years of participation in a behavioral intervention program designed for toddlers (16). The AAP recommends that infants and toddlers suspected of having an ASD be referred immediately to an early intervention program (2).
There is no cure for ASDs. However, some children benefit from medications that help improve their behavioral symptoms so that they are better able to learn. Some commonly used medications include:
- Anti-depressants and anti-anxiety drugs.
- Anti-psychotics: A new anti-psychotic drug called risperidone (Risperdal) is the only drug that is approved by the Food and Drug Administration (FDA) specifically for autistic behaviors, such as aggression, self-injury and temper tantrums (5).
- Stimulants: One such medication is Ritalin, which is commonly prescribed for attention deficit hyperactivity disorder (ADHD).
Some children with ASDs are treated with alternative therapies, such as a strict eating plan, vitamins and detoxification therapies (such as the drug treatment called chelation which reduces the amount of mercury and other metals in the body). To date, there is no evidence to show these treatments are helpful (17). Parents who are interested in alternative treatments should discuss the possible risks and benefits with their child’s health care provider.
Does the March of Dimes support research on ASDs?
The March of Dimes supports a number of grantees who are studying the role of specific genes in brain development for insight into how abnormalities may cause ASDs. Study results could provide the basis for developing new treatments for ASDs. Another grantee is studying differences in how autistic children process information and pay attention, in order to develop improved educational interventions.
Where can I find more information on autism spectrum disorders?
- Autism Spectrum Disorders (U.S. Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities)
- Autism Fact Sheet (National Institute of Neurological Disorders and Stroke)
- Autism (American Academy of Pediatrics)
- Centers for Disease Control and Prevention (CDC). (2009). Autism spectrum disorders.
- Johnson, C.P., Myers, S.M. and the Council on Children with Disabilities. (2007). Identification and evaluation of children with autism spectrum disorders. Pediatrics, 120 (5), 1183-1215.
- Centers for Disease Control and Prevention (CDC). (2009). Prevalence of autism spectrum disorders – autism and developmental disabilities monitoring network, United States, 2006. Morbidity and Mortality Weekly Report, 58 (SS-10).
- Kogan, M.A., Blumberg, S.J., Schieve, L.A., Boyle, C.A., Perrin, J.M., et al. (2009). Prevalence of parent-reported diagnosis of autism spectrum disorder among children in the U.S., 2007. Pediatrics, 124 (5), 1395-1403.
- National Institute of Child Health & Human Development (2005). Autism Research at the NICHD.
- Limperopoulos, C., Bassan, H., Sullivan, N.R., Soul, J.S., Robertson, R.L., et al. (2008). Positive screening for autism in ex-preterm infants: prevalence and risk factors. Pediatrics, 121 (4), 758-765.
- Johnson, S., Hollis, C., Kochhar, P., Hennessy, E., Wolke, D., & Marlow, N. (2010). Autism spectrum disorders in extremely premature children. Journal of Pediatrics online.
- Kuban, K.C., O’Shea, T.M., Allred, E.N., Tager-Flusberg, H., Goldstein, D.J. & Leviton, A. (2009). Positive screening on the modified checklist for autism in toddlers (M-CHAT) in extremely low gestational age newborns. Journal of Pediatrics, 154 (4), 535-540.
- Buchmayer, S., Johansson, S., Johansson, A., Hultman, C.M., Sparen, P. & Cnattinguis, S. (2009). Can association between preterm birth and autism be explained by maternal or neonatal morbidity? Pediatrics, 124 (5), e817-825.
- Wang, K., Zhang, H., Ma, D., Bucan, M., Glessner, J.T., et al. (2009). Common genetic variants on 5p14.1 associate with autism spectrum disorders. Nature.
- Weiss, L.A., Shen, Y., Korn, J.M., Arking, D.E., Miller, D.T., et al. (2008). Association between microdeletion and microduplication at 16p11.2 and autism. New England Journal of Medicine, 358 (7), 667-675.
- Shelton, J.F., Tancredi, D.J. & Hertz-Picciotto. (2010). Independent and dependent contributions of advanced maternal and paternal ages to autism risk. Autism Research.
- Editors of The Lancet. (2010). Retraction—Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. The Lancet.
- Institute of Medicine. (2004). Immunization safety review: vaccines and autism. New York: National Academies Press.
- Schechter, R. & Grether, J. (2008). Continuing increases in autism reported to California’s developmental services system. Archives of General Psychiatry, 65 (1), 19-24.
- Dawson, G., Rogers, S., Munson, J., Smith, M., Winter, J., et al. (2010). Randomized, controlled trial of an intervention for toddlers with autism: the Early Start Denver model. Pediatrics, 125 (1), e7-e23.
- Myers, S.M., Johnson, C.P., and the Council on Children with Disabilities. (2007). Management of children with autism spectrum disorders. Pediatrics, 120 (5), 1162-1182.