Autism is a disorder that affects the social, emotional, and behavioral development of children. Autism is marked by serious difficulties in interacting and communicating with other people. Other symptoms may include constantly repeating certain actions or behaviors, or having intense interests restricted to only particular things or topics. Symptoms of autism usually appear before the age of three and can last the rest of a person’s lifetime. Autism is at least four times more common in boys than in girls.
The term autism comes from Greek auto, meaning “self,” and refers to an abnormal withdrawal from the world outside oneself. The American psychiatrist Leo Kanner first described the disorder in 1943. Autism was originally thought to be a form of schizophrenia, but it has been recognized since the 1960s as a distinct developmental disorder that is not a psychosis. Modern researchers now identify a wide “spectrum” of autism symptoms that may occur in different combinations or with different severities in children.
The causes of autism remain a major area of research and of controversy. Studies indicate that autism is often associated with abnormalities in the functioning of the brain and that the disorder may have a genetic basis in most cases.
Raising a child with autism can present special challenges for a family. There is no cure for autism, but some treatments and therapies can lessen the symptoms. Some persons with autism may need special care throughout their lives while others may learn to function independently in society.
The number of children diagnosed with autism has increased since the 1990s. Until the mid-1990s, autism was estimated to occur in 1 in 3,000 children. More recent estimates suggest that autism occurs in approximately 1 in 500 children, and that 1 in 150 children may be on the “autism spectrum” with one or more symptoms. An estimated 560,000 children in the United States may have autism spectrum disorders.
Possible reasons why more cases of autism are being reported include dramatically improved and standardized methods for diagnosing autism, along with increased awareness of autism, first among the medical community and then in the media. Children and adults with less severe symptoms are more likely to be diagnosed with autism today than they were 15 years ago.
On the other hand, some researchers believe that the greater number of autism diagnoses represents a true increase in the incidence of the disorder and points to some environmental factor that may have changed over the same period of time. Although no scientific data currently support a connection with autism, possible environmental factors proposed include toxic chemicals, vaccines, pollutants, food products, and prenatal exposure to certain drugs or infectious agents.
A still unexplained feature of autism is the much higher incidence of the disorder in boys, about four times as frequent as in girls. Girls with autism, however, tend to show more severe symptoms and mental impairment.
The diagnosis of autism—officially called “autistic disorder” (AD)—is based upon the American Psychiatric Association’s definition of three symptoms areas: (1) social difficulties, (2) communication difficulties, and (3) restrictive interests or repetitive behaviors. Symptoms from all three of these areas must be present before the age of three to make a diagnosis of autism. Most children with autism show developmental delays from the infant or toddler period. In some cases, however, children with autism suffer a regression, or loss of skills, after a period of normal development.
Symptoms of social difficulty are usually the first signs of autism. Normally an infant should respond to others with a social smile within the second or third month of life. Lack of such a smile during this period is often the earliest indication of autism. Infants who are later diagnosed with autism also make poor eye contact and do not imitate caregiver sounds or gestures.
Children with autism typically do not share their enjoyment with others. For example, toddlers with autism may smile or laugh in response to a noisy toy, but they will not bring this toy to the caregiver. Another early sign of problems in social communication is a lack of gestures, including pointing. As they get older, children with autism often fail to develop typical friendships or even typical relationships with siblings or parents. They may also seem unaware of the feelings of other people or fail to comfort a person who is upset.
Children with autism have difficulties with communication, including both gestures and speech. Often children with autism have a delay in speech and in severe cases sometimes do not speak at all. They also fail to use gestures to replace words. How well children with autism will be able to function as they grow older can often be predicted based on their early language skills.
When children with autism are able to speak, they may repeat back exactly what is said to them, a behavior that is called echolalia. Sometimes they will quote whole conversations or a dialog from a movie. Frequently, children with autism misuse pronouns. For example, they may say, “You want a cookie?” to indicate that they want a cookie. As they get older, children with autism will be unable to have conversations with others. They will also not play make-believe but instead will often simply line up objects or replay a TV show or movie using their toys.
The restricted interests or repetitive behaviors that often occur in autism are sometimes the least obvious symptoms when children are toddlers. These symptoms usually become a larger problem around the age of four or five.
Many children with autism will have a limited number of intense interests, such as dinosaurs, trains, or characters from a cartoon. They may also be preoccupied with parts of objects. For example, they may spin the wheel of a toy car instead of pretending to drive it.
Frequently, children with autism will insist on doing things in exactly the same way or on following the same routine from day to day. As a result, they may become very upset in response to a minor change, such as not having their usual breakfast cereal or taking a different route when driving home from school. Children with autism may also repeat body movements, such as spinning, rocking, or flapping hands.
When upset or excited, they may also harm themselves by skin-biting or head-banging. They may also show significant aggression toward other people or inanimate objects, or may have episodes of extreme anger or frustration.
Some children with autism show other symptoms that do not contribute to the diagnosis of autism itself.
Sensory sensitivity is quite common, especially to some textures, sounds, or smells. For example, many children with autism cannot tolerate the feeling of tags or labels attached to their clothing. Some children may be alarmed by common sounds such as a flushing toilet or falling rain. They may react to ordinary smells such as perfume or discarded food as disgusting or overwhelming.
Problems with belly pain, constipation, or diarrhea are frequently reported. These problems may sometimes be due to encopresis, a painful but treatable condition caused by a partial blockage of the large intestine with hard stool. Some reports also suggest an increase in allergies and in problems with the immune system.
Mental Retardation and Savant Skills
Prior to the 1990s, three-quarters of children with autism were also diagnosed with mental retardation. The increase in autism diagnosis, however, has been matched by a decrease in the number of children with autism who are also considered to have mental retardation. Children with autism can have wide variations in their intellectual abilities. Many show a decrease in verbal intelligence—that is, their ability to understand and use words. On the other hand, some children with Asperger’s syndrome, who have intact speech and language comprehension, show difficulties in nonverbal intelligence, particularly understanding cause-and-effect relationships. For example, a person with Asperger’s might not understand that a mother feeding a baby would quiet the baby down and stop it from crying. Due to the wide variation in abilities, every child with autism should have intelligence testing.
Some people with autism show preserved ability in one area or demonstrate a particular skill, such as memorizing phone numbers, computing calendar dates, or drawing landscapes. These preserved or enhanced abilities are described as savant skills and are responsible for the conception of the “autistic savant” as popularized in movies such as Rainman (1988). Although approximately 10 percent of people with autism show a preserved skill that is outstanding in comparison to their overall function, truly exceptional skills or talents are quite rare.
DIAGNOSING AUTISM AND RELATED DISORDERS
Most children with autism or a related disorder show some but not all symptoms of the disorder. It is important to have a thorough evaluation with a psychologist or physician to get a clear diagnosis and treatment plan.
Classic autism, termed autistic disorder, is one of five disorders making up the pervasive developmental disorders (PDDs). Two other diagnoses, Asperger’s syndrome and PDD not otherwise specified (PDD-NOS), are considered part of the “autism spectrum.” The remaining two diagnoses for PDDs, Rett syndrome and childhood disintegrative disorder, are much rarer and have a worse prognosis.
When children do not have communication problems and have average intelligence but do have autistic symptoms in social and behavioral areas, they may be diagnosed with Asperger’s syndrome. Hans Asperger, an Austrian psychiatrist, first described children with this cluster of symptoms in 1944. Autism and Asperger’s syndrome are often difficult to separate. A careful history may reveal that a child who does not have communication problems at 10 years old did have a significant language delay or cannot have a conversation except when talking about a restricted interest, such as dinosaurs or cartoon characters. Children diagnosed with Asperger’s syndrome often use unusual words and may sound old-fashioned or as if they are reading out of a textbook. Sometimes this unusual language is actually delayed echolalia, where they are repeating back something that they heard or read word-for-word.
Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS)
Many children have symptoms in one or two of the three symptom areas but do not show enough symptoms for the diagnosis of autistic disorder or Asperger’s syndrome. These children are typically diagnosed with pervasive developmental disorder not otherwise specified (PDD-NOS) and are often described as being on the “autism spectrum.” Children with this diagnosis can be very different from one another. Additionally, it is often difficult to separate children who have PDD-NOS from children who have speech or language problems that result in difficulty forming relationships. The particular areas of difficulty should be used to shape the goals for each individual child, both at home and at school.
Rett syndrome is a severe disorder that affects only girls. Although it progresses from symptoms resembling autism, it is not classified as part of the autism spectrum. Symptoms include characteristic hand movements, loss of language and motor skills, seizures, and eventually death from irregular breathing.
Childhood Disintegrative Disorder
Childhood disintegrative disorder (CDD) is diagnosed in children who develop symptoms similar to autism after a two- to four-year period of apparent normal development. Such children may then lose such basic abilities as language, self-care, and toilet use. They also lose interest in their social and even physical environment. Because the onset and course of CDD are distinct from autism, it is not considered part of the autism spectrum. The prognosis for CDD is also worse than for autism—CDD usually results in very severe impairment.
Distinctness of Autism
A number of the symptoms associated with autism also occur in other developmental or behavioral disorders, and in certain mental illnesses. However, the special combination of symptoms and their severity set autism apart.
Severe social withdrawal is found in schizophrenia—in fact, autism was originally misclassified as a type of childhood schizophrenia. However, the symptoms of schizophrenia typically develop in adolescence or later, and can include bizarre behavior or delusions that do not otherwise impair intelligence and communication capabilities. Medications can often reduce symptoms of schizophrenia to a point where a person with the illness can function and communicate relatively normally. The causes of schizophrenia appear to be biological, affecting the development and functioning of the brain.
Mental retardation is associated with a range of disorders, but the behaviors characteristic of autism may not be present. For example, children with Down syndrome have serious language and other cognitive difficulties. In most cases, however, they do not suffer the kind of social withdrawal characteristic of autism and instead can be highly affectionate and responsive to others. Down syndrome is caused by a clearly identified chromosomal disorder and results in distinctive changes in facial features.
Children with Tourette’s syndrome, a neurological disorder characterized by involuntary body movements and vocal outbursts, may engage in repetitive actions or have sudden, violent tantrums. However, their intelligence and their social and emotional development are typically normal.
Forms of serious self-destructive behavior such as head-banging, scratching or biting oneself, and using objects in the environment to cut or injure oneself, are also associated with a number of disorders, including several genetic disorders such as Lesch-Nyhan syndrome, fragile X syndrome, and Cornelia de Lange syndrome. Other types of destructive or aggressive behavior, including violent tantrums, can have many causes, including reactions to child abuse or emotional stress.
Researchers are unlikely to find a single cause in the majority of cases of children with autism. With a better understanding of the causes, autism may prove to be a number of separate disorders with different risk factors that lead to a similar pattern of problems. According to current research, most cases of autism almost certainly have a biological basis that involves brain abnormalities and genes.
The term autism was originally proposed in 1911 by the Swiss psychiatrist Eugen Bleuler to describe a common feature of schizophrenia in adults—extreme withdrawal from social contact with others. Schizophrenia is a severe mental illness in which a person is often cut off from reality.
The American psychiatrist Leo Kanner used the term autism in its modern sense in 1943 for a disorder found in children, which he termed “an extreme autistic aloneness.” Kanner and many of his colleagues originally viewed autism as a subtype of schizophrenia, and thus a psychosis.
Soon after Leo Kanner’s original description of autism in 1943, the idea arose that autism was caused by a mother’s lack of warmth and connection to her infant. This idea appears in Kanner’s descriptions of autism but was expanded by Bruno Bettelheim, an Austrian-born child psychologist who popularized the term refrigerator mother. The idea of bad parenting causing autism was not only damaging to countless families but also false.
Beginning in the 1960s and the early 1970s a new view of autism emerged. Scientists recognized autism in children as a disorder distinct from schizophrenia, and not a psychosis. Additionally, the likely cause of autism was shifted to neurological abnormalities, not poor parenting. Continuing research has supported these ideas and has provided many important insights into possible biological bases for the disorder.
Studies of Twins
Studies of identical and fraternal twins have demonstrated that genetic factors are the largest cause of autism. Beginning with a pioneering study by Susan Folstein and Michael Rutter in 1977, these studies found that identical twins share an autism diagnosis much more frequently than fraternal twins—identical twins have exactly the same DNA while fraternal twins have only half the same DNA.
If one identical twin is diagnosed with autism, the other identical twin will also be diagnosed with autism 60 percent of the time, and with symptoms of an autism spectrum disorder more than 90 percent of the time. In comparison, if a fraternal twin is diagnosed with autism, the other twin will have symptoms of an autism spectrum disorder only 10 percent of the time.
These numbers can be used to estimate that genetic risk determines at least 90 percent of the time whether a child will develop autism. This pattern of genetic risk predicts that variation in more than one gene is necessary to cause risk of autism. This does not rule out environmental causes but points to genetics as the primary cause. Additionally, change in the methods of autism diagnosis or in the frequency of autism in the population would lead to a change in the estimate of genetic risk.
Genetic Disorders with Autistic Symptoms
Several rare genetic disorders that cause developmental problems in multiple organs of the body also include autistic symptoms.
Rett syndrome is classified as one of the five pervasive developmental disorders (PDDs), along with autism. Rett syndrome is caused by mutations in the MECP2 gene on the X chromosome. It is a severe disorder found only in girls and progresses from symptoms of autism to seizures, and eventual death from irregular breathing.
Fragile X syndrome affects primarily boys and is caused by a variation in the FMR1 gene on the X chromosome. Affected boys have mental retardation, a long face, large ears, enlarged testes, and often social difficulties and hyperactivity.
Smith-Lemli-Opitz syndrome, which results from a defect in the cholesterol pathway, leads to a small head, a distinctive facial appearance (upturned nose and undersized lower jaw), and finger abnormalities, but it also includes autistic symptoms in most children. Many other genetic syndromes include autistic features as part of a larger cluster of developmental abnormalities.
A few rare genetic causes of autism have been found that do not lead to problems in other organs. A couple of these rare mutations affect genes such as NLGN4 and SHANK3 that are involved in connecting neurons to each other. Another set of rare genetic variations in the SLC6A4 gene increase the activity of the serotonin transporter protein that pulls serotonin into platelets and neurons, which may explain a portion of the patients with hyperserotonemia. The risk of autism is doubled in children who inherit a common variation of the MET gene, which is important for growth of the cerebellar vermis, a structure connecting the two lobes of the cerebellum in the brain. Several other genes may also increase the risk of autism, but researchers have not yet identified which variations in the genes are responsible.
Many theories have been proposed to explain what goes wrong during brain development to cause autism. Research has centered on a number of factors that may be involved.
Serotonin is a neurotransmitter that is produced in the brain. It has a range of functions in the body, including important roles in the central nervous system. It also affects mood, memory, and appetite control. In 1961 Daniel Freedman and colleagues found increased levels of serotonin in the blood of patients with autism. More recent research has found that increased serotonin, or hyperserotonemia, is present in about one-quarter of patients, is also present in some of their family members, and is caused by genetic factors.
Some children with autism show an increase in brain growth during the first year of life that later slows down so that most adults with autism do not have enlarged brains. This increased growth is thought to be due to increased connections between neurons. Most brain studies in autism have also found a decrease in the size of a particular brain region, the cerebellar vermis.
People with autism show less activity than normal in the mirror neuron system of the brain that some scientists believe allows the human brain to understand and learn from observing other people. A recent theory proposed that defects in the mirror neuron system may explain some aspects of autism. Additionally, people with autism often overreact emotionally to trivial events in their environments, suggesting a problem with the processing of what they perceive.
Many theories have been proposed to explain each of these findings, but more research is needed to understand what goes wrong during brain development.
Infections and Drugs
In rare cases, children born to mothers who were infected with certain illnesses or took particular drugs during pregnancy may have autism as part of a larger set of difficulties. For example, infection with German measles (rubella) during pregnancy affects the heart, liver, spleen, eyes, and brain, and includes features of autism more commonly than other causes of mental retardation. In developed countries, however, the widespread use of vaccines has almost eliminated rubella infection during pregnancy.
Exposure to the seizure medication valproate can affect the development of the spinal cord (spina bifida), heart, lungs, and other organs, and may also lead to an increased risk of autistic features. Rates of autism in children exposed to valproate during pregnancy are difficult to calculate and appear to be quite low.
There are no known cures for autism or autism spectrum disorders. Until the 1960s and even into the early 1970s, children and adults with autism were routinely kept in institutions. Now children with autism are often raised at home by their parents. Many adults with forms of autism can live in the outside world with some type of assistance. Currently, treatment includes the use of individualized education, communication tools, behavioral management, and medication. The devastating impact the disorder can have on children and families has led some parents to try many unproven treatments in the hope of a breakthrough or major improvement.
The mainstays of treatment for autism include interpersonal, behavioral, and communication principles all applied toward educational goals. Parents, teachers, and therapists need to work together to help a child gain new skills and abilities. Several approaches are being used to work toward these goals.
Therapy and Training Approaches
Ivar Lovaas, an American psychologist, pioneered a behavioral modification system that includes immediate rewards and punishments to shape a child’s behavior. A controversial aspect of this approach is the use of electric shock to deter self-destructive behavior in extreme cases.
The Treatment and Education of Autistic and Related Communication-Handicapped Children (TEACCH) system uses a picture schedule of time-limited tasks to gradually build on skills while also including well-liked tasks as a reward.
The Floortime system uses frequent play sessions with a parent to connect therapy goals with activities that a child finds exciting or fun, ideally gaining skills and developing a deeper relationship with a parent at the same time. Other systems have also been applied, but it is not yet clear whether any one approach is better than another.
Medication is not a primary treatment for autism itself but can be helpful for related symptoms.
Risperidone (Risperdal) received Food and Drug Administration (FDA) approval in 2006 for “irritability” in autism and is the first medication to receive FDA approval in treatment of the disorder. Most of the children in the studies of risperidone treatment had significant aggression toward themselves or others or episodes of extreme anger or frustration. Risperidone may have significant side effects including weight gain, risk of diabetes, and movement disorders.
A group of medications called the serotonin reuptake inhibitors have been used successfully to treat compulsive behaviors in autism. These medications include fluoxetine (Prozac), fluvoxamine (Luvox), and escitalopram (Lexapro). Some children experience decreased sleep and agitation on these medications, and the dose needs to be carefully monitored by an experienced clinician.
A number of other medications may also be used in children with autism, particularly when they also have extreme hyperactivity, poor sleep, or aggression. No medication has been shown to have significant effects on the social or communication difficulties seen in autism.
Many clinicians and parents have looked to alternative treatments for autism. These treatments often have no scientific basis or offer no evidence that they are effective. Approaches such as providing special vitamin supplements or making dietary changes should cause no serious harm to children in most cases, although some proposed diets can lead to vitamin deficiencies. Most concerning, however, are invasive treatments such as heavy metal chelation. Chelation therapy uses chemicals to remove heavy metals such as mercury and cadmium from the body. The treatment has caused the death of at least one child with autism without having any known benefit.
EDUCATION OF CHILDREN WITH AUTISM
The educational needs of children with autism are variable. Some children require a self-contained classroom with all special education classes. Others can be included in mainstream classrooms with little or no support. Treatment principles from programs such as TEACCH or Lovaas can be included in the school day. No single approach will be right for every child with autism. Federal law obligates public schools to assess each child’s individual needs and provide an appropriate educational setting to meet those needs.
LIFE FOR ADULTS WITH AUTISM
How a person with autism functions in adult life depends greatly on language skills and intelligence. Some people with so-called high-functioning autism are able to live and work independently. In some cases, adults with forms of autism have pursued professional careers such as veterinary medicine, mathematics, or writing. Adults with Asperger’s syndrome can develop special strategies to overcome problems with memory or with understanding emotions in others. For example, a computer program was recently developed to help teach adults with autism how to interpret facial expressions in others.
Adults with more severe autism may require significant social support in a residential community. Those with limited speech often need close supervision, either within a family or in a group home or other residential placement. The best jobs for most adults with autism have clear rules, may include a particular skill or interest, and do not include complex social interactions.
Autism is a devastating disorder whose cause remains poorly understood. It is not surprising that some clinicians and families develop strong opinions about possible causes or treatments. These opinions sometimes generate considerable interest in the popular media and sometimes attract a good deal of research funding to prove or disprove them.
One such idea was the fear that vaccines somehow lead to autism. Initially, fear focused on the idea of persistent infection from the measles-mumps-rubella vaccine. More recently, concerns were raised about a vaccine preservative, thimerosal, that contains ethylmercury. No scientific research supports either idea and, to the contrary, vaccines have nearly eliminated congenital rubella, one of the few known environmental causes of autism.
Others fear that exposure to heavy metals such as mercury and cadmium could lead to autism and advocate chelation treatment, which uses chemicals to remove heavy metals from the body. Synthetic chemical compounds cited as possible triggers for autism have included flame retardants, pesticides, fertilizers, and even food additives such as aspartame. The frequent occurrence of gastrointestinal symptoms in autism leads some to advocate for various diets that remove wheat products, dairy products, or even all carbohydrates. There is currently no firm scientific evidence that any of these substances are involved in causing autism.
The increase in children diagnosed with autism has led to calls for more government funding for research into autism and for special help for parents of children with autism. Public schools face major challenges as more children with symptoms of autism or autism spectrum disorders are enrolled. Society will also need to deal with adults who have symptoms of autism that may qualify as disabilities in the workplace or elsewhere.