What causes autism?

Since autism was first added to the psychiatric literature fifty years ago, there have been numerous studies and theories about its cause. Researchers still have not reached agreement regarding its specific causes. First, it must be recognized that autism is a set of a wide variety of symptoms and may have many causes. This concept is not unusual in medicine. For instance, the set of symptoms that we perceive of as a “cold” can be caused by literally hundreds of different viruses, bacteria, and even our own immune system. Autism is, undoubtedly, a biologically-based disorder. In the past, some researchers had suggested that autism was the result of poor attachment skills on the part of the mother. This belief has caused a great deal of unnecessary pain and guilt on the part of the parents of autistic children, when in fact, the inability of the individual with autism to interact appropriately is one of the key symptoms of this developmental disorder.

In support of a biological theory of autism, several known neurological disorders are associated with autistic features. Autism is one of the symptoms of these disorders. These conditions include tuberous sclerosis (an inherited disorder), the fragile X syndrome, cerebral dysgenesis (abnormal development of the brain), Rett syndrome, and some of the inborn errors of metabolism (biochemical defects). Autism, in short, seems to be the end result or “final common pathway” of numerous disorders that affect brain development. In general, however, when clinicians make the diagnosis of autism, they are excluding the known causes of autistic behaviors. However, as the knowledge of conditions that cause autism advances, fewer and fewer cases will be thought of as being “pure” autism and more individuals will be identified as having autism due to specific causes.

There is a strong association between autism and seizures. This association works in two ways: First, many patients (20% to 30%) with autism develop seizures. Second, patients with seizures, which are probably due to other causes, may develop autistic-like behaviors. One special and often misunderstood association between autism and seizures is the Landau-Kleffner Syndrome. This syndrome is also known as acquired epileptic aphasia. Some children with epilepsy develop a sudden loss of language skills–especially receptive language (the ability to understand). Many often also develop the symptoms of autism.

These children often, but not always, have a characteristic pattern of electrical brain activity seen on EEG (electroencephalogram) during deep sleep called electrographic status epilepticus during sleep (ESES). The usual age of onset of language loss or regression is around four years of age, which makes the Landau-Kleffner syndrome distinguishable from autism on these grounds, in that autism usually is first exhibited in younger children. However, in recent years, some children (very, very few) who did not exhibit overt (observable) seizures were found to have Landau-Kleffner syndrome.

The importance of these findings is that, although rare, the Landau-Kleffner syndrome can resolve spontaneously and in some cases can be treatable with prednisone, a steroid medication related to cortisone. This association between the Landau-Kleffner syndrome and autism has led many clinicians and families to search for the typical EEG pattern (ESES) in autistic individuals. This unusual EEG pattern is seen only in deep sleep, which usually requires prolonged recordings of up to 12 hours. Many, many autistic children and adults will display some abnormalities on their sleep EEG, but probably very few have true Landau-Kleffner syndrome that will respond to treatment.

It must also be noted that prednisone, in the very high doses used to treat Landau-Kleffner syndrome, almost invariably produces side effects, which may include weight gain, high blood pressure, diabetes, growth failure, stomach ulcers, irritability, destruction of the hip joint, and susceptibility to infectious disease (suppressed immune system). While most of these side effects are reversible, some of the complications of high dose prednisone therapy can be irreversible and even fatal.

Other treatments ranging from common anticonvulsant therapy to surgery have been proposed and are being tried for Landau-Kleffner syndrome. It is difficult to evaluate the true effects of any treatment for Landau-Kleffner syndrome due to the high rate of spontaneous resolution of symptoms (remission).

The Symptoms of Autism

The current Diagnosis and Statistical Manual of Mental Disorders-Fourth Edition, Treatment Revision (DSM-IV-TR) identifies three features that are associated with autism:

  • impairment in social interaction,
  • communication, and
  • Behavior.

Impairment in social interaction

First, patients with autism fail to develop normal personal interactions in virtually every setting. This means that affected persons fail to form the normal social contacts that are such an important part of human development. This impairment may be so severe that it even affects the bonding between a mother and an infant. It is important to note that, contrary to popular belief, many, if not most, autistic persons are capable of showing affection and do demonstrate affection and do bond with their mothers or other caregivers. However, the ways in which autistic individuals demonstrate affection and bonding may differ greatly from the ways in which others do so. Their limited socialization may erroneously lead parents and pediatricians away from considering the diagnosis of autism. As the child develops, interaction with others continues to be abnormal. Affected behaviors can include eye contact, facial expressions, and body postures. There is usually an inability to develop normal peer and sibling relationships and the child often seems isolated. There may be little or no joy or interest in normal age-appropriate activities. Affected children or adults do not seek out peers for play or other social interactions. In severe cases, they may not even be aware of the presence of other individuals.

Communication

Communication is usually severely impaired in autistic persons. What the individual understands (receptive language) as well as what is actually spoken by the individual (expressive language) is significantly delayed or nonexistent. Deficits in language comprehension include the inability to understand simple directions, questions, or commands. There may be an absence of dramatic or pretend play and these children may not be able to engage in simple age-appropriate childhood games such as Simon Says or Hide-and-Go-Seek. Adults may continue to engage in playing with games that are for young children.

Autistic individuals who do speak may be unable to initiate or participate in a two-way conversation (reciprocal). Frequently the way in which an autistic person speaks is perceived as unusual. Their speech may seem to lack the normal emotion and sound flat or monotonous. The sentences are often very immature: “want water” instead of “I want some water please.” Those with autism often repeat words or phrases that are spoken to them. For example, you might say “look at the airplane!” and the child or adult may respond “at airplane,” without any knowledge of what was said. This repetition is known as echolalia. Memorization and recitation of songs, stories, commercials, or even entire scripts is not uncommon. While many feel this is a sign of intelligence, the autistic person usually does not appear to understand any of the content in his or her speech.

Autistic persons often exhibit a variety of repetitive, abnormal behaviors. There may also be a hypersensitivity to sensory input through vision, hearing, or touch (tactile). As a result, there may be an extreme intolerance to loud noises or crowds, visual stimulation, or things that are felt. Birthday parties and other celebrations can be disastrous for some of these individuals. Tags on clothing may be perceived as painful. Sticky fingers, playing with modeling clay, eating birthday cake or other foods, or walking barefoot across the grass can be unbearable. On the other hand, there may be an underdeveloped (hyposensitivity) response to the same type of stimulation. This individual may use abnormal means to experience visual, auditory, or tactile (touch) input. This person may head bang, scratch until blood is drawn, scream instead of speaking in a normal tone, or bring everything into close visual range. He or she might also touch an object, image or other people thoroughly just to experience the sensory input.

Autistic children and adults are often tied to routine and many everyday tasks may be ritualistic. Something as simple as a bath may only be accomplished after the precise amount of water is in the tub, the temperature is exact, the same soap is in its assigned spot and even the same towel is in the same place. Any break in the routine can provoke a severe reaction in the individual and place a tremendous strain on the adult trying to work with them.

There may also be non-purposeful repetition of actions or behaviors. Persistent rocking, teeth grinding, hair or finger twirling, hand flapping and walking on tiptoe are not uncommon. Frequently, there is a preoccupation with a very limited interest or a specific plaything. A child or adult may continually play with only one type of toy. The child may line up all the dolls or cars and the adult line up their clothes or toiletries, for example, and repeatedly and systematically perform the same action on each one. Any attempt to disrupt the person may result in extreme reactions on the part of the autistic individual, including tantrums or direct physical attack. Objects that spin, open and close, or perform some other action can hold an extreme fascination. If left alone, an autistic person may sit for hours turning off and on a light switch, twirling a spinning toy, or stacking nesting objects. Some individuals can also have an inappropriate bonding to specific objects and become hysterical without that piece of string, paper clip, or wad of paper.

Scare Anatomy

Like many people in London on that bleak February day in 1998, biochemist Nicholas Chadwick was eager to hear what the scientists would say. The Royal Free Hospital, where he was a graduate student in the lab of gastroenterologist Andrew Wakefield, had called a press conference to unveil the results of a new study. With flashbulbs popping, Wakefield stepped up to the bank of microphones: he and his colleagues, he said, had discovered a new syndrome that they believed was triggered by the MMR (measles, mumps, rubella) vaccine. In eight of the 12 children in their study, being published that day in the respected journal The Lancet, they had found severe intestinal inflammation, with the symptoms striking six days, on average, after the children received the MMR. But hospitals don’t hold elaborate press conferences for studies of gut problems. The reason for all the hoopla was that nine of the children in the study also had autism, and the tragic disease had seized them between one and 14 days after their MMR jab. The vaccine, Wakefield suggested, had damaged the intestine—in particular, the measles part had caused serious inflammation—allowing harmful proteins to leak from the gut into the bloodstream and from there to the brain, where they damaged neurons in a way that triggered autism. Although in their paper the scientists noted that “we did not prove an association” between the MMR and autism, Wakefield was adamant. “It’s a moral issue for me,” he said, “and I can’t support the continued use of [the MMR] until this issue has been resolved.”

That’s strange, thought Chadwick. For months he had been extracting genetic material from children’s gut biopsies, looking for evidence of measles from the MMR. That was the crucial first link in the chain of argument connecting the MMR to autism: the measles virus infects the gut, causing inflammation and leakage, then gut leakage lets neurotoxin compounds into the blood and brain. Yet Chadwick kept coming up empty-handed. “There were a few cases of false positives, [but] essentially all the samples tested were negative,” he later told a judicial hearing. When he explained the negative results, he told NEWSWEEK, Wakefield “tended to shrug his shoulders. Even in lab meetings he would only talk about data that supported his hypothesis. Once he had his theory, he stuck to it no matter what.” Chadwick was more disappointed than upset, figuring little would come from the Lancet study. “Not many people thought [Wakefield] would be taken that seriously,” Chadwick recalls. “We thought most people would see the Lancet paper for what it was—a very preliminary collection of [only 12] case reports. How wrong we were.”

The next day, headlines in the British press screamed, DOCTORS LINK AUTISM TO MMR VACCINE AND BAN THREE-IN-ONE JAB, URGE DOCTORS AFTER NEW FEARS. That was mild compared with what followed. Hysteria over childhood vaccinations built to such a crescendo that Wakefield’s nuanced warning—that it was specifically the triple vaccine, not single-disease vaccines (even measles), that posed a threat—was drowned out. In 2001, Prime Minister Tony Blair and his wife, Cherie, refused to say whether their son, then 19 months old, had received the MMR; rumors swirled that they had gone to France so the child could receive the measles vaccine alone. In 2003, a docudrama about Wakefield ran on British TV, depicting him as having his files stolen and his phone tapped by evil pharmaceutical companies intent on protecting their vaccines. As one reviewer described the show: “The MMR vaccine is coming to get our kids.”

vaccines (of which U.S. health officials recommend 35 by age 6) started a backlash in the United States, too, fueled in no small part by the fact that the incidence of autism was rising for reasons scientists could not fully explain. In California, for instance, the incidence of autism had risen from 6.2 per 10,000 births in 1990 to 42.5 in 2001. Groups of parents began refusing vaccines for their children. Within a few years of Wakefield’s announcement, rates of MMR vaccinations in Britain fell from 92 percent to below 80 percent. Although there was no comparable nationwide decrease in the United States, pockets of resistance to vaccination appeared throughout the country, laying the groundwork for a sevenfold increase in measles outbreaks. Looking back from the perspective of 11 years, the panic seems both inevitable and inexplicable. Inevitable, because legitimate scientists publishing in respected journals produced evidence of a link between vaccines and autism, and because the press as well as politicians and even public-health officials stoked the mounting hysteria. Inexplicable because, by the early 2000s, scientific support for that link had evaporated as completely as the red dot on a baby’s vaccinated thigh.

Scientists and government officials who defended the safety of childhood vaccines were not shy about attributing the fears to the science illiteracy of the public and the fear mongering of the press. In truth, however, after Wakefield’s announcement there was a steady drumbeat of studies—not from kooks in basement labs but from real scientists working at real institutions and publishing in real, peer-reviewed journals—that backed him up. In 2002, pathologist John O’Leary of Coombe Women’s Hospital in Dublin reported that he had found RNA from the measles virus in 7 percent of normal children—but in 82 percent of those with autism, suggesting that some children are unable to clear the vaccinated virus from their systems, resulting in autism. That same year, a Utah State University biologist reported finding high levels of antibodies against the measles virus in the blood and spinal fluid of autistic children; the MMR, he postulated, had triggered a hyper immune response that attacked the children’s brains. In 2003, gastroenterologist Arthur Krigsman, then at New York University School of Medicine, reported finding what Wakefield had: that the guts of 40 autistic children were severely inflamed, lending support to the idea that leaks allowed pernicious compounds to make a beeline for the brain.

But these studies and others supporting the link between autism and the MMR were nothing compared with an extraordinary step that had been taken by the U.S. government and by one of the country’s leading medical organizations. On July 7, 1999, the American Academy of Pediatrics (AAP) and the U.S. Public Health Service issued a warning about the preservative in many vaccines. Called thimerosal, it contains 49.6 percent ethyl mercury by weight and had been used in vaccines since the 1930s, including the diphtheria/tetanus/pertussis (DTP) and Haemophilus influenzae (Hib) vaccines (but not the MMR). The experts tried to be reassuring, saying in a statement there are “no data or evidence of any harm” from thimerosal. But, they continued, children’s cumulative exposure to mercury from vaccines “exceeds one of the federal safety guidelines” for mercury. (By 2003, most childhood vaccines did not contain thimerosal, though flu vaccines still did.) The AAP statement did not mention autism

Characteristic Behaviors of Autism

Autism is characterized by three distinctive behaviors. Autistic children:

  • Have difficulties with social interaction
  • Display problems with verbal and nonverbal communication
  • Exhibit repetitive behaviors or narrow, obsessive interests.

Some people with the condition can function at a relatively high level, with speech and intelligence intact. Others have serious cognitive impairments and language delays, and some never speak.

In addition, individuals with autism may seem closed off and shut down, or locked into repetitive behaviors and rigid patterns of thinking. An infant may avoid eye contact, seem deaf, and abruptly stop developing language. The child may act as if unaware of the coming and going of others, or physically attack and injure others without provocation. Infants with autism often remain fixated on a single item or activity, rock or flap their hands, seem insensitive to burns and bruises, and may even mutilate themselves.

What Causes It?

Scientists aren’t certain what cause autism, but it’s likely that both genetics and environment play a role.

Treatment for Autism

There is no cure for the disorder. Therapies and behavioral interventions are designed to remedy specific symptoms and can bring about substantial improvement.

The ideal treatment plan coordinates therapies and interventions that target the core symptoms of the condition:

  • Impaired social interaction
  • Problems with verbal and nonverbal communication
  • Obsessive or repetitive routines and interests.

Most professionals agree that the earlier the intervention, the better.