Autism: Risk Factors & Diagnosis

Who Is At Risk?

Studies measuring autism spectrum disorder (ASD) prevalence—the number of children affected by ASD over a given time period—have reported varying results, depending on when and where the studies were conducted and how the studies defined ASD.

A survey by the Centers for Disease Control and Prevention (CDC)  of health and school records of 8-year-olds in 11 communities throughout the country found that in 2010, the rate of ASD was higher than in past U.S. studies, around 1 in 68 children. Boys face about four to five times higher risk than girls.

Experts disagree about whether this shows a true increase in ASD prevalence. Since the earlier studies were completed, guidelines for diagnosis have changed. Also, many more parents and doctors now know about ASD, so parents are more likely to take their children to be diagnosed, and more doctors are able to properly diagnose ASD. These and other changes may help explain some differences in prevalence numbers. Even so, the CDC report confirms other recent studies showing that more children are being diagnosed with ASD than ever before. For more information, please visit the autism section of the CDC website .

Diagnosis

Autism spectrum disorder (ASD) diagnosis is often a two-stage process. The first stage involves general developmental screening during well-child checkups with a pediatrician or an early childhood health care provider. Children who show some developmental problems are referred for additional evaluation. The second stage involves a thorough evaluation by a team of doctors and other health professionals with a wide range of specialties. At this stage, a child may be diagnosed as having ASD or another developmental disorder.

Children with ASD can usually be reliably diagnosed by age 2, though research suggests that some screening tests can be helpful at 18 months or even younger. Many people—including pediatricians, family doctors, teachers, and parents—may minimize signs of ASD at first, believing that children will "catch up" with their peers. While you may be concerned about labeling your young child with ASD, the earlier the disorder is diagnosed, the sooner specific interventions may begin. Early intervention can reduce or prevent the more severe disabilities associated with ASD. Early intervention may also improve your child's IQ, language, and everyday functional skills, also called adaptive behavior.

Screening

A well-child checkup should include a developmental screening test, with specific ASD screening at 18 and 24 months as recommended by the American Academy of Pediatrics. Screening for ASD is not the same as diagnosing ASD. Screening instruments are used as a first step to tell the doctor whether a child needs more testing. If your child's pediatrician does not routinely screen your child for ASD, ask that it be done.

For parents, your own experiences and concerns about your child's development will be very important in the screening process. Keep your own notes about your child's development and look through family videos, photos, and baby albums to help you remember when you first noticed each behavior and when your child reached certain developmental milestones.

Types of ASD screening instruments

Sometimes the doctor will ask parents questions about the child's symptoms to screen for ASD. Other screening instruments combine information from parents with the doctor's own observations of the child. Examples of screening instruments for toddlers and preschoolers include:

  • Checklist of Autism in Toddlers (CHAT)
  • Modified Checklist for Autism in Toddlers (M-CHAT)
  • Screening Tool for Autism in Two-Year-Olds (STAT)
  • Social Communication Questionnaire (SCQ)
  • Communication and Symbolic Behavior Scales (CSBS).
  • To screen for mild ASD in older children, the doctor may rely on different screening instruments, such as:
  • Autism Spectrum Screening Questionnaire (ASSQ)
  • Australian Scale for Asperger's Syndrome (ASAS)
  • Childhood Asperger Syndrome Test (CAST).

Some helpful resources on ASD screening include the Center for Disease Control and Prevention's General Developmental Screening tools and ASD Specific Screening tools on their website .

Comprehensive diagnostic evaluation

The second stage of diagnosis must be thorough in order to find whether other conditions may be causing your child's symptoms.

A team that includes a psychologist, a neurologist, a psychiatrist, a speech therapist, or other professionals experienced in diagnosing ASD may do this evaluation. The evaluation may assess the child's cognitive level (thinking skills), language level, and adaptive behavior (age-appropriate skills needed to complete daily activities independently, for example eating, dressing, and toileting).

Because ASD is a complex disorder that sometimes occurs along with other illnesses or learning disorders, the comprehensive evaluation may include brain imaging and gene tests, along with in-depth memory, problem-solving, and language testing. Children with any delayed development should also get a hearing test as part of the comprehensive evaluation.

Although children can lose their hearing along with developing ASD, common ASD symptoms (such as not turning to face a person calling their name) can also make it seem that children cannot hear when in fact they can. If a child is not responding to speech, especially to his or her name, it's important for the doctor to test whether a child has hearing loss.

The evaluation process is a good time for parents and caregivers to ask questions and get advice from the whole evaluation team. The outcome of the evaluation will help plan for treatment and interventions to help your child. Be sure to ask who you can contact with follow-up questions.

What are some other conditions that children with ASD may have?

Sensory problems

Children with autism spectrum disorder (ASD) either overreact or underreact to certain sights, sounds, smells, textures, and tastes. For example, some may:

  • Dislike or show discomfort from a light touch or the feel of clothes on their skin
  • Experience pain from certain sounds, like a vacuum cleaner, a ringing telephone, or a sudden storm; sometimes they will cover their ears and scream
  • Have no reaction to intense cold or pain.
  • Researchers are trying to determine if these unusual reactions are related to differences in integrating multiple types of information from the senses.

Sleep problems

Children with ASD tend to have problems falling asleep or staying asleep, or have other sleep problems. These problems make it harder for them to pay attention, reduce their ability to function, and lead to poor behavior. In addition, parents of children with ASD and sleep problems tend to report greater family stress and poorer overall health among themselves.

Fortunately, sleep problems can often be treated with changes in behavior, such as following a sleep schedule or creating a bedtime routine. Some children may sleep better using medications such as melatonin, which is a hormone that helps regulate the body's sleep-wake cycle. Like any medication, melatonin can have unwanted side effects. Talk to your child's doctor about possible risks and benefits before giving your child melatonin. Treating sleep problems in children with ASD may improve the child's overall behavior and functioning, as well as relieve family stress.

Intellectual disability

Many children with ASD have some degree of intellectual disability. When tested, some areas of ability may be normal, while others—especially cognitive (thinking) and language abilities—may be relatively weak. For example, a child with ASD may do well on tasks related to sight (such as putting a puzzle together) but may not do as well on language-based problem-solving tasks. Some children with ASD (such as those formerly diagnosed with Asperger’s syndrome) often have average or above-average language skills and do not show delays in cognitive ability or speech.

Seizures

One in four children with ASD has seizures, often starting either in early childhood or during the teen years. Seizures, caused by abnormal electrical activity in the brain, can result in

  • A short-term loss of consciousness, or a blackout
  • Convulsions, which are uncontrollable shaking of the whole body, or unusual movements
  • Staring spells

Sometimes lack of sleep or a high fever can trigger a seizure. An electroencephalogram (EEG), a nonsurgical test that records electrical activity in the brain, can help confirm whether a child is having seizures. However, some children with ASD have abnormal EEGs even if they are not having seizures.

Seizures can be treated with medicines called anticonvulsants. Some seizure medicines affect behavior; changes in behavior should be closely watched in children with ASD. In most cases, a doctor will use the lowest dose of medicine that works for the child. Anticonvulsants usually reduce the number of seizures but may not prevent all of them.

For more information about medications, see the NIMH online booklet, "Mental Health Medications". None of these medications have been approved by the FDA to specifically treat symptoms of ASD.

Fragile X syndrome

Fragile X syndrome is a genetic disorder and is the most common form of inherited intellectual disability, causing symptoms similar to ASD. The name refers to one part of the X chromosome that has a defective piece that appears pinched and fragile when viewed with a microscope. Fragile X syndrome results from a change, called a mutation, on a single gene. This mutation, in effect, turns off the gene. Some people may have only a small mutation and not show any symptoms, while others have a larger mutation and more severe symptoms.

Around 1 in 3 children who have Fragile X syndrome also meet the diagnostic criteria for ASD, and about 1 in 25 children diagnosed with ASD have the mutation that causes Fragile X syndrome. Because this disorder is inherited, children with ASD should be checked for Fragile X, especially if the parents want to have more children. Other family members who are planning to have children may also want to be checked for Fragile X syndrome. For more information on Fragile X, see the Eunice Kennedy Shriver National Institute of Child Health and Human Development website .

Tuberous sclerosis

Tuberous sclerosis is a rare genetic disorder that causes noncancerous tumors to grow in the brain and other vital organs. Tuberous sclerosis occurs in 1 to 4 percent of people with ASD. A genetic mutation causes the disorder, which has also been linked to intellectual disability, epilepsy, and many other physical and mental health problems. There is no cure for tuberous sclerosis, but many symptoms can be treated.

Gastrointestinal problems

Some parents of children with ASD report that their child has frequent gastrointestinal (GI) or digestion problems, including stomach pain, diarrhea, constipation, acid reflux, vomiting, or bloating. Food allergies may also cause problems for children with ASD. It's unclear whether children with ASD are more likely to have GI problems than typically developing children. If your child has GI problems, a doctor who specializes in GI problems, called a gastroenterologist, can help find the cause and suggest appropriate treatment.

Some studies have reported that children with ASD seem to have more GI symptoms, but these findings may not apply to all children with ASD. For example, a recent study found that children with ASD in Minnesota were more likely to have physical and behavioral difficulties related to diet (for example, lactose intolerance or insisting on certain foods), as well as constipation, than children without ASD. The researchers suggested that children with ASD may not have underlying GI problems, but that their behavior may create GI symptoms—for example, a child who insists on eating only certain foods may not get enough fiber or fluids in his or her diet, which leads to constipation.

Some parents may try to put their child on a special diet to control ASD or GI symptoms. While some children may benefit from limiting certain foods, there is no strong evidence that these special diets reduce ASD symptoms. If you want to try a special diet, first talk with a doctor or a nutrition expert to make sure your child's nutritional needs are being met.

Co-occurring mental disorders

Children with ASD can also develop mental disorders such as anxiety disorders, attention deficit hyperactivity disorder (ADHD), or depression. Research shows that people with ASD are at higher risk for some mental disorders than people without ASD. Managing these co-occurring conditions with medications or behavioral therapy, which teaches children how to control their behavior, can reduce symptoms that appear to worsen a child's ASD symptoms. Controlling these conditions will allow children with ASD to focus more on managing the ASD.

Related disorders

Rett syndrome is another developmental disorder which includes a regression in development. Only 1 of every 10,000 to 22,000 girls has Rett syndrome.

Unlike ASD, Rett syndrome mostly affects girls. In general, children with Rett syndrome develop normally for 6–18 months before regression and autism-like symptoms begin to appear. Children with Rett syndrome may also have difficulties with coordination, movement, and speech. Physical, occupational, and speech therapy can help, but no specific treatment for Rett syndrome is available yet.

With funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, scientists have discovered that a mutation in the sequence of a single gene is linked to most cases of Rett syndrome. This discovery may help scientists find ways to slow or stop the progress of the disorder. It may also improve doctors' ability to diagnose and treat children with Rett syndrome earlier, improving their overall quality of life.