Welcome to Your Child's Brain: How the Mind Grows From Conception to College (42 page)

Evidence that autistic toddlers experience social sensory experiences in an unusual way comes from watching their reactions. They show difficulties with detecting natural biological motion such as walking, as well as with interpreting common social cues. When adults speak, typical toddlers look at the speaker’s eyes, which convey social information. Autistic toddlers tend to look directly at the mouth, where the sound is coming from. In one study, toddlers saw a movie, with a soundtrack, of lights attached to various points on a model’s head and body while he played a make-believe game with a teddy bear. Autistic toddlers spent equal amounts of time looking at the video played forward and the same
video played upside-down and backward, so that the audio and visuals were mismatched. Typical and nonautistic disabled children focused mostly on the right-side-up movie.

At autism’s core is a deficit in
theory of mind
, the ability to imagine what other people know and what they are thinking or feeling.

Perceptual difficulties persist throughout development and into adulthood. Autistic people often show a high degree of sensitivity to routine sounds and even the sensation of their own clothing. Temple Grandin writes of her own experience as an autistic person: “Loud noises were also a problem, often feeling like a dentist’s drill hitting a nerve. They actually caused pain. I was scared to death of balloons popping … Minor noises that most people can tune out drove me to distraction … My roommate’s hairdryer sounded like a jet plane taking off.” L. H. Willey, who has Asperger’s syndrome, writes: “I found it impossible even to touch some objects. I hated stiff things, satiny things … Goose bumps and chills and a general sense of unease would follow.”

In identical twins, if one twin is autistic, the probability that the other is autistic is between 60 and 90 percent. Nonidentical twins, who share only half their genetic material with each other, have a much lower rate of diagnostic concordance. These facts suggest that autism’s roots are genetic, and that they involve multiple genes. Researchers have been able to find warning signs as early as one to four months of age, indicating that developmental consequences of such a genetic inheritance can appear very early in life.

In recent years, genes that are associated with a higher likelihood of autism have begun to be found. Some of these genes are involved in brain development. Others encode proteins that are found at synapses, suggesting that they may affect the development or some other function of synaptic connections. Often one of these genes is present in some quantity other than the usual two (one from Mom and one from Dad), in a phenomenon called
copy number variation
. Although it is not clear exactly how these genes increase the risk of autism, in most cases autism is caused by combinations of genes. It may be that if neurodevelopmental processes encounter multiple difficulties, a sufficiently large perturbation will cause the brain to veer away from a typical path and toward autism spectrum disorder. Dozens of susceptibility genes have been found so far.

PRACTICAL TIP: BEHAVIORAL THERAPY IS HELPFUL IF STARTED EARLY

Many therapies have been tried to treat the problems of autism, ranging from the mainstream to the speculative (see
p. 239
). The evidence that these treatments work is weak at best. The notable exception is intensive behavioral therapy, for which the most evidence for efficacy exists. Intensive behavioral therapy takes several forms and can help about half of autistic children.

In the 1970s and 1980s, Ivar Lovaas and his collaborators at the University of California, Los Angeles, developed a therapy for autistic children consisting of intensive one-on-one instruction, supervised training play sessions with typical (unimpaired) children, inclusion in regular classroom activities, and parent training for further at-home therapy. This intensive approach improves function in autistic children.

Behavioral therapy can begin as soon as autism is diagnosed, usually at age two or three. The UCLA model starts by getting children to respond to unambiguous instruction, starting with simple tasks. Correct responses are initially rewarded by foods and desirable sensory and perceptual objects. Later the children feel rewarded by praise, tickling, hugs, and kisses. Once they can answer questions, take turns, and engage in basic play, they are paired with typical children who give feedback during supervised play. Eventually the autistic child is introduced to classroom situations and group play.

Compared with other therapies or regular special education, children receiving behavioral therapy are more socially engaged and have better language, with improvements in IQ averaging twenty points. However, behavioral therapy is expensive and arduous. The cost is approximately $50,000 per year. Even this large cost may be less expensive than caring for an autistic person over his or her lifetime. Therapy requires at least thirty hours per week of direct attention by clinic staff or by parents working under staff supervision. Focus is required; in moderately impaired autistic children aged four to seven, combining behavioral therapy with other approaches has been reported to be far less effective, perhaps because efforts to give the effective therapy are diluted.

Given the developmental history of autism, it would seem logical to start therapy as early as possible. One research team described Catherine, the one-year-old sister of an autistic child. Catherine obsessively closed open doors, had little language, and spent much of her time balancing long objects such as rulers vertically on her hand. Catherine underwent intensive treatment for three years, after which she entered regular kindergarten and tested above average in cognitive and language skills. At the end, Catherine blended in with typical children. Efforts are now under way to test the effectiveness of very early intervention.

Although this anecdotal case cannot prove whether Catherine would have otherwise become autistic, her successful outcome does suggest the potential benefit of identifying children at risk for autism before the age of two. Catherine’s case may also demonstrate that a sufficiently mild dose of autism susceptibility genes may carry “orchid” advantages (see
Practical tip: Dandelion and orchid children
) under suitable conditions, as evidenced by her eventual above-average performance.

One question is why the genetic factors that underlie autism would persist in the population. After all, aren’t these the kinds of defects that disappear through evolution? This is generally the case, but an important exception occurs when combinations of genes cause a problem but confer some benefit individually. A well-known example is the gene for the oxygen transport protein hemoglobin. When a child inherits one copy that is altered in a particular way, he has increased resistance to malaria. When both copies are altered, sickle-cell anemia results.

Similarly, individual autism risk genes may have other functional effects. For example, autistic people tend to be very good with details, perhaps because of a lack of higher control from the frontal cortex. A small number of people in the population with an exceptional ability to focus on tasks could be a good thing for those people—and for society. In the words of Temple Grandin, “What would happen if the autism gene was eliminated from the gene pool? You would have a bunch of people standing around chatting and socializing and not getting anything done.”

Another consequence of carrying autism susceptibility genes is an enhanced
likelihood of interest in technical fields. Sam recently surveyed an entire entering freshman class at Princeton University. He found that among students expressing an interest in a technical field (science, engineering, or mathematics), one in twenty-five reported having a sibling with autism spectrum disorder. This rate was over three times as high as that found for aspiring humanities and social science majors, one in eighty-two. Similarly, in a previous study, physics and math majors at the University of Cambridge reported having relatives with autism spectrum disorder far more often than English and French majors did. These findings suggest the possibility that autism susceptibility genes might lead to a predisposition to a particular characteristic of thought, such as looking for systematic explanations for events in the world (or conversely, a predisposition not to think in terms of social explanations).

Autism is triggered largely by genetics.

Autism does not occur together in every pair of identical twins, suggesting that environmental causes may also contribute to the disorder. These environmental effects probably act during early infancy or even before birth. One example is the drug Depakote (valproic acid), which is given for epilepsy and psychiatric illness. It can increase the rate of autism when mothers take it during pregnancy. Another example is prenatal stress in the fifth, sixth, or ninth month of gestation, which is associated with a higher rate of autism (see
Practical tip: Less stress, fewer problems
).

Despite reports to the contrary, it is a myth that autism can be triggered by vaccination. In the 1990s, specific blame was leveled at a particular vaccine, MMR, which is typically given at the age of twelve months. The original report was widely covered in the popular press. However, the paper was retracted and found to be fraudulent, events that have garnered less media attention.

A detailed investigation showed that the researcher Andrew Wakefield falsified the medical records of every child in the study, for instance, concealing the fact that children showed signs of autism before being vaccinated or were not autistic at all. Nearly all of the children were referred to Wakefield by a lawyer who was paying him to conduct the study to aid a lawsuit against vaccine manufacturers. Wakefield was stripped of his clinical and academic credentials, but
continues to push a vaccine-autism connection in the U.S. with supporters such as the celebrity Jenny McCarthy. In several communities where the MMR vaccine has been withheld, the rate of autism has stayed the same, and in some cases the rate has increased. Since the developmental steps leading to autism are already well under way before the age of one, the main effect of withholding vaccination is to increase the risk of disease to your child and to his friends.

Even though the genetic causes of autism are starting to be understood, effective treatment is far off. Currently, autism has no silver bullet. One treatment that yields some positive outcomes is behavioral therapy. Unfortunately, this can be a hard road (see
Practical tip: Behavioral therapy is helpful if started early
).

Some of parents’ motivation to determine the causes of autism and seek treatment for their children may come from a feeling of guilt, even though they are not at fault in any way. Although these efforts are essential in driving forward research into causes and treatments, parents should be careful about embracing unproven and pricey new treatments, many of which have no benefit. Examples include chelation and nutritional therapy, facilitated communication, and hyperbaric oxygen treatment—the list goes on. These treatments are unlikely to be any better for a child than doing nothing, and in some cases they carry a significant risk of harm (see
Practical tip: Spotting untrustworthy treatments
).

For autistic children, the strongest contribution that parents can make is to recognize the potential for problems early in life—and to act by the age of two, or earlier if possible. In most cases, babies simply mature on their own timetables, but for this disorder, intervention can make a critical difference. The challenges posed by autism spectrum disorder are considerable and will be with us for the foreseeable future. However, considering the possible benefits seen in their non-autistic relatives, some of the genes that make children autistic may also help others to thrive and contribute to society.

Chapter 28
OLD GENES MEET THE MODERN WORLD: ADHD

AGES: EIGHT YEARS TO EIGHTEEN YEARS

When Charlie Gross was a boy in the 1950s, he was deemed hyperactive. Although he was bright, his teachers bored him, so he was considered to be a troublesome child. He found other challenges, becoming an Eagle Scout and winning the Westinghouse Science Talent Search as a high school student. Years later, as a leading brain researcher, he was the first to discover single neurons in primate brains that respond to complex features, such as faces (see
chapter 25
).

If he had been born fifty years later, there is little doubt that he would have been offered treatment for ADHD. This disorder is estimated to occur in 5 percent of children worldwide. A looser definition gives an estimate as high as 17 percent, and in some school systems, up to 20 percent of boys receive drug treatment for this disorder. Is a phenomenon that is so widespread—yet so variable in estimated occurrence and treatment—a clearly defined medical disorder?