Autism is a complex brain disorder that affects many aspects of child development, including how a kid talks, plays, and interacts. Although the causes of autism are not yet fully understood, experts agree that the earlier autistic children receive treatment for their symptoms, the better. Early intervention makes a huge difference in the outcome of the disorder, so as a parent, it's important to know autism’s warning signs and seek immediate help if you spot them in your child.

Understanding autism

Autism is a disorder that appears in early childhood, causing delays in many basic areas of development such as learning to talk and interact with others. The symptoms of autism vary widely, as does the impact of the disorder: some autistic children have only mild impairments, while others have more obstacles to overcome. But although the specific combination of symptoms and the severity of the disorder differ from person to person, kids with autism typically have problems in the following three areas:

  • Social Skills — Impaired social interaction is the hallmark sign of autism. This may appear as an apparent lack of interest in other people and the surrounding environment. Children with autism often appear to be in their own little world. They have trouble engaging in back-and-forth play, sharing emotions, making friends, and understanding what others are thinking and feeling.
  • Communication — Autism also involves problems with verbal and nonverbal communication. Spoken language is usually delayed in autistic children and may even be completely absent. Even when able to speak, children with autism usually have trouble conversing freely and easily. Other common symptoms involve odd or repetitive speech patterns, inappropriate facial expressions and gestures, and language comprehension difficulties.
  • Repetitive behavior — Autistic children often exhibit repetitive or "stereotyped" behaviors and narrow, restricted interests. This may show up as an extreme resistance to change, obsessive attachments to unusual objects, or inflexible routines and schedules. Repetitive body movements, or self-stimulatory behaviors, such as hand flapping and rocking are also common.

There is some debate over how many people have autism and whether or not the disorder is becoming more prevalent. While more children are being diagnosed with autism than in the past, many experts believe that at least some of the increase can be explained by heightened public awareness of the disorder, as well as broader and more accurate diagnostic criteria that is catching milder cases.

On the other hand, the latest research indicates that—at the very least—autism is more common in the U.S. than previously thought. According to a February 2007 report from the Centers for Disease Control and Prevention (CDC), 1 in 150 children has autism.

While autism occurs with equal frequency across all races, ethnicities, and social classes, boys are three to four times more likely to have autism than girls. The siblings of those with the disorder are also at a higher risk.

One Baby's Story

Melanie is a healthy one-year-old, but her parents are worried because she’s not doing many things that her older brother did at her age. When he was one, Melanie’s brother loved to play peek-a-boo and mimic his mom’s expressions and gestures. Melanie, on the other hand, rarely makes eye contact or responds when her parents call her name. Furthermore, she doesn’t babble or make other baby noises. Her mom and dad try to engage her with toys, songs, and games, but nothing they do gets her interest, let alone a laugh or a smile.

Melanie’s parents have been waiting for her to catch up, but the gap between her and others her age is only getting wider. Last week, Melanie and her mom went to the zoo with some families from the neighborhood. The other babies pointed excitedly at the animals and stared in wide-eyed wonder, but Melanie didn’t pay any attention to either the exotic animals or the other group members. At the end of the day, one of the kids banged his knee and started crying. The other babies looked distressed and many started crying themselves. Melanie didn’t even seem to notice what was going on.

The Autism Spectrum Disorders

Autism is one of a group of developmental disorders known as the autism spectrum disorders (ASDs). All of the ASDs begin in childhood and involve delays in communication and social skills. They are known as spectrum disorders because every child on the autism spectrum is affected differently, with unique challenges, symptoms, and abilities.

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Causes of autism

The causes of autism are unknown, but most experts agree that both genetic and environmental factors are involved. One popular theory is that certain individuals are born with a genetic predisposition for autism that is then triggered by something in the environment, either while the baby is still in the womb or shortly after birth.

Genetic causes of autism

Research indicates that genes—particularly inherited genetic glitches and spontaneous DNA mutations—play a primary role in the development of autism. But no single gene is to blame. Scientists believe that at least 5 to 20 major genes are involved in autism, with many others also contributing to the risk.

The bulk of the evidence for autism’s hereditary component comes from twin studies. Multiple twin studies show that when one identical twin develops autism, the other twin will also develop the disorder approximately 9 times out of 10. In fraternal twins—who are no more genetically similar than normal siblings—the concordance rate is just 1 in 10.

Large epidemiologic studies also show that older parents are at a significantly higher risk of having autistic children. The age of the father appears to be particularly important. A recent Israeli study found that children born to fathers who were 40 or older were almost six times more likely to develop autism than the children of men younger than 30. This heightened risk is likely due to genetic mutations in sperm, which are more and more common as men age.

But while some specific chromosomal abnormalities and mutations appear to cause autism themselves, in the majority of cases, the interaction of multiple genes leads to a susceptibility to autism without directly causing it.

Environmental causes of autism

Since genes don’t completely explain autism risk or the rising number of new cases, scientists are searching for environmental explanations to fill in the blanks. The idea is that toxins, chemicals, or other harmful external elements may trigger autism, either by “turning on” or exacerbating a genetic vulnerability or independently disturbing brain development.

While considerable attention has been focused on vaccines as a possible cause of autism, a growing body of research suggests that the disorder is caused by environmental factors that occur before vaccination, and sometimes even before birth.

Evidence suggests that autism can be triggered by exposure—either during pregnancy or the early months of life­—to viral infections, pesticides, insecticides, and the prescription drugs thalidomide and valproic acid. Recent studies have also found that oxygen deprivation during delivery or fetal development can up the risk of autism.

Other environmental factors being studied include air pollution, food additives, mercury in fish, flame retardants, and certain chemicals used to make plastics and other synthetic materials. These substances are particularly dangerous to young babies, whose brains are more likely to absorb toxins and less effective at clearing them out.

Autism and vaccines

When it comes to autism, no topic is more controversial than childhood vaccinations. At the center of this controversy is thimerosal, a mercury-containing preservative once commonly used in vaccines to prevent bacterial and fungal contamination. The concern is that exposure to thimerosal may lead to mercury poisoning and autism. Scientific research, however, does not support the theory that childhood vaccinations cause autism.

Five major epidemiologic studies conducted in the U.S., the U.K., Sweden, and Denmark found that children who received vaccines containing thimerosal did not have higher rates of autism. Additionally, a major safety review by the Institute of Medicine failed to find any evidence supporting the connection. Other organizations that have concluded that vaccines are not associated with autism include the Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug Administration (FDA), the American Academy of Pediatrics, and the World Health Organization.

With the exception of the flu vaccine, thimerosal is no longer used in any childhood vaccines. If you remain concerned about a possible connection between autism and mercury, you can request a thimerosal-free version of the flu vaccine from your child's pediatrician.

Early signs and symptoms of autism

Autism symptoms are usually apparent by 18 to 36 months of age, and subtle warning signs may be evident much earlier—even as early as infancy. Because early intervention makes a huge difference in minimizing the symptoms and negative impact of autism, the earlier autism is identified the better. As a parent, you’re much more likely to catch the early signs and symptoms of autism if you track your child’s development, watching out for developmental delays and red flags.

Developmental delays as a sign of autism

As children grow, they go through a process where fundamental skills, or developmental milestones, are learned and mastered. These milestones include: physical skills (such as sitting up, crawling, and walking), social skills (such as smiling, playing, and imitating others), and communication skills (such as gesturing and talking). Since the pace of growth varies from child to child, there are flexible windows of time where certain developmental milestones should be reached. However, if your child has not reached milestones at the expected age, this indicates a developmental delay.

Autism involves a multitude of developmental delays, so keeping a close eye on when—or if—your child is hitting all the key social, emotional, and cognitive milestones is an effective way to spot the problem early on. While developmental delays don’t automatically point to autism, they do indicate a heightened risk. Furthermore, whether the delay is caused by autism or some other factor, developmentally delayed kids are unlikely to simply “grow out” of the problem. In order to develop skills in an area of delay, your child needs extra help and targeted treatment.

The following delays warrant an immediate evaluation by your child’s pediatrician:

  • By 6 months: No big smiles or other warm, joyful expressions.

  • By 9 months: No back-and-forth sharing of sounds, smiles, or other facial expressions.

  • By 12 months: No babbling or “baby talk.”

  • By 12 months: No back-and-forth gestures, such as pointing, showing, reaching, or waving.

  • By 16 months: No spoken words.

  • By 24 months: No meaningful two-word phrases that don’t involve imitating or repeating.

  • At any age: Any loss of speech, babbling, or social skills.

Source: First Signs

Regression of any kind should be taken seriously. According to Catherine Lord, the director of the University of Michigan Autism and Communication Disorders Center, about 25% of autistic kids appear normal as babies and then regress at some point between 12 and 24 months. For example, a child who was communicating with words such as “mommy” or “up” may stop using language entirely, or a child may stop playing social games he or she used to enjoy such as peek-a-boo, patty cake, or waving “bye-bye.”

Detecting autism in babies

Most children are diagnosed with autism around the age of three. However, when autism is detected even earlier, treatment can take full advantage of the young brain’s remarkable plasticity. If detected by 12 months of age or even earlier, intensive treatment may even be able to rewire the brain and reverse the symptoms.

However, the earliest signs of autism are easy to miss because they involve the absence of normal behaviors—not the presence of abnormal ones. For example, autistic babies typically don’t follow moving objects with their eyes, reach out to grasp toys, or make gestures to attract attention. In some cases, the earliest symptoms of autism are even misinterpreted as signs of a “good baby,” since the infant is quiet and doesn’t make demands. But while such a baby may be easy to deal with, these are red flags of a very serious problem, not positive qualities.

Babies—like all humans—are social creatures. By the time they are 2 to 3 months old, babies who are developing normally will make sounds to get their parents attention, smile at the sound of a familiar voice, play with other people, and imitate certain movements and facial expressions. If your baby isn’t responding to you, despite your attempts to interact and show affection, it is cause for concern.

Other early signs of autism:

  • The baby doesn’t make eye contact.
  • The baby doesn't respond to his or her name.
  • The baby doesn’t follow objects visually.
  • The baby doesn't smile when smiled at.
  • The baby doesn’t imitate other people.
  • The baby doesn't point or wave goodbye.
  • The baby doesn’t babble or make noises.

According to Harvard Medical School, babies who are passive and inactive at 6 months, then extremely irritable or joyless at 12 months, are also at a higher risk of developing autism.

The First Sign of Autism

A study published in the April 2007 issue of Archives of Pediatrics and Adolescent Medicine found that the failure to turn or look in response to hearing one’s name may be one of the earliest signs of autism.

Autism red flags in children of all ages

As children get older, the red flags for autism increase and become more diverse. There are many warning signs and symptoms, but they typically revolve around verbal and non-verbal communication difficulties, impaired social skills, and repetitive behaviors.

Verbal warning signs and symptoms of autism:

  • Slow to develop language skills.
  • Repeats or echoes certain words or phrases.
  • Has trouble expressing needs.
  • Used to say a few words or babble, but doesn't anymore.

Non-verbal warning signs and symptoms of autism:

  • Avoids eye contact.
  • Doesn’t play "pretend" games.
  • Reacts unusually to sights, smells, textures, and sounds.
  • Doesn’t seem to hear when others talk to him or her.

Social warning signs and symptoms of autism:

  • Appears uninterested in other people.
  • Has trouble understanding or talking about feelings.
  • Doesn’t know how to talk to or play with others.
  • Prefers not to be held or cuddled.

Repetitive behavior warning signs and symptoms of autism:

  • Has difficulty adapting to changes in routine.
  • Shows unusual attachments to toys or other objects.
  • Obsessively lines things up or arranges them in a certain order
  • Repeats the same actions or movements over and over again.

What to do if you 're worried

If your young child or baby is delayed in any area or if you’ve observed red flags or other warning signs for autism, schedule an immediate appointment with your pediatrician. In fact, it’s a good idea to have your child screened by a doctor even if he or she is hitting the developmental milestones on schedule. The American Academy of Pediatrics recommends that all children receive routine developmental screenings, as well as specific screenings for autism at 9, 18, and 30 months of age.

Autism Screening

Online Screening Tools for Autism

A number of specialized screening tools have been developed to identify children at risk for an autism spectrum disorder. Most of these screening tools are quick and straightforward, consisting of yes-or-no questions or a checklist of symptoms.

The pediatrician should also get your feedback regarding your child’s behavior. If you aren’t asked about your specific concerns, don’t be afraid to speak up. No one knows your child better than you.

If the pediatrician sees possible signs of autism, your child should be referred to a specialist for a comprehensive diagnostic evaluation. Screening tools can’t be used to make a diagnosis, which is why further assessment is needed.

Getting Immediate Help for Your Child

The diagnostic process for autism is tricky, and sometimes it can take awhile. But you don’t have to wait for an official diagnosis before you begin to get help for your child. Ask your doctor to refer you to early intervention services. Early intervention is a federally-funded program for infants and toddlers with disabilities.

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Related links for autism

General information about autism

Autism Overview: What We Know (PDF) – Comprehensive overview of autism’s causes, symptoms, prevalence, and treatment. (National Institute of Child Health and Human Development)

Autism: Enigma and Stigma – Article describes what life is like for individuals with autism. Includes a history of the disorder and a description of the symptoms. (University of Alabama, Birmingham)

Autism Spectrum Disorders (Pervasive Developmental Disorders) – Learn the signs and symptoms of autism and other pervasive developmental disorders. Includes information about causes and treatment. (National Institute of Mental Health)

Early warning signs and symptoms of autism

First Signs - Non-profit organization dedicated to educating parents and pediatric professionals about the early warning signs of autism and other developmental disorders. Helpful articles include Hallmark Developmental Milestones and Early Intervention.

Learn the Signs. Act Early. – Government resource on child development, including important developmental milestones and warnings signs and symptoms of developmental delays. (Centers for Disease Control)

Early Features of Autism – Fact sheet from the Australian Child to Adult Development Study covers the early warning signs and symptoms of autism. (ACT-NOW)

Autism: Recognizing the Signs in Young Children – Covers early red flags for autism and the reasons why early diagnosis is so important. (The National Autistic Society)

Autism screening

Sharing Concerns: Parent to Physician - Features tips on how to effectively communicate with the doctor regarding your concerns about your child. (First Signs)

Screening: Making Observations – Overview of developmental screening and how they can identify autism and other problems early. (First Signs)

Making Early Developmental Screenings Routine – Article on early developmental screenings for autism and how you can be an advocate for your child. (Connect for Kids)

Causes of autism

Searching for Early Signs of Autism Spectrum Disorders – Covers the latest research on autism’s genetic and environmental causes. (Pri-Med Patient Education Center)

Autism and Genes (PDF) – Comprehensive look at the genetic factors involved in autism. Includes information about current research. (National Institute of Child Health and Human Development)

Focus Narrows in Search for Autism's Cause – Learn about evidence into autism’s causes, including abnormal brain development and connectivity abnormalities. (New York Times)

Time to Get a Grip (PDF) – Article by a Harvard Medical School neurology professor on the role of the environment in triggering autism. (Autism Advocate)

Environmental Health and Autism FAQ – Browse through frequently asked questions concerning environmental health and autism. (Autism Society of America)

Out of Sync? – Discover how faulty brain wiring may cause some of the problems seen in autism. (Psychology Today)

Study Provides Evidence That Autism Affects Functioning of Entire Brain – Reviews evidence that autism involves difficulties on complex tasks where various parts of the brain have to work together. (National Institutes of Health News)

Autism and vaccines

What Parents Should Know About Thimerosal – FAQ on thimerosal in vaccines, the dangers of mercury, and studies on the link between autism and vaccines. (American Academy of Pediatrics)

On Autism's Cause, It's Parents vs. Research – Learn about the heated debate over the theory that mercury-containing vaccines cause autism. (New York Times)

Thimerosal and Autism – This Vaccine Education Center article looks into the proposed connection between thimerosal and autism. (The Children’s Hospital of Philadelphia)

Thimerosal in Vaccines – In-depth government fact sheet on thimerosal-containing vaccines and concerns about autism. (U.S. Food and Drug Administration)

Autism prevalence rates

Autism's So-Called Epidemic – Article argues that the rise in incidence of autism cases could be due to better diagnostic skills. (Psychology Today)

Is Autism on the Rise? – Article looks at the rising prevalence rates and whether or not this indicates a true spike in cases of autism. (Association for Science in Autism Treatment)