It has been over 75 years since Dr. Leo Kanner, a psychiatrist at Johns Hopkins University, wrote the first paper applying the term ‘autism’ to a group of children who were self-absorbed and who had severe social, communication, and behavioral problems. This paper provides a general overview of the complexity of this developmental disability by summarizing many of the major topics in autism.


For many years, the most cited statistic is that autism occurs in 4.5 out of 10,000 live births. This was based on large-scale surveys conducted in the United States and England. More recently, estimates on the prevalence of autism have ranged been as high as 1/4% to 1/2% of the population. These estimates typically include those with autism, Asperger syndrome, and PDD. In 2015 the CDC announced that autism affects 1 in 59 Americans.

Autism is three times more likely to affect males than females. This gender difference is not unique to autism since many developmental disabilities have a greater male to female ratio.

Major Characteristics

Many autistic infants are different from birth. Two common characteristics they may exhibit include arching their back away from their caregiver to avoid physical contact and failing to anticipate being picked up (i.e., becoming limp). As infants, they are often described as either passive or overly agitated babies. A passive baby refers to one who is quiet most of the time making little, if any, demands on his/her parents. An overly agitated baby refers to an infant who cries a great deal, sometimes non-stop, during his/her waking hours. During infancy, many begin to rock and/or bang their head against the crib; but this is not always the case.

In the first few years of life, some autistic toddlers reach developmental milestones, such as talking, crawling, and walking, much earlier than the average child; whereas others are considerably delayed. Approximately one-half of autistic children develop normally until somewhere between 1 1/2 to 3 years of age; then autistic symptoms begin to emerge. These individuals are often referred to as having ‘regressive’ autism. Some people in the field believe that children with ‘regressive’ autism may have Landau-Kleffner Syndrome.

During childhood, autistic children may fall behind their same-aged peers in the areas of communication, social skills, and cognition. In addition, dysfunctional behaviors may start to appear, such as self-stimulatory behaviors (i.e., repetitive, non-goal directed behavior, such as rocking, hand-flapping), self-injury (e.g., hand-biting, headbanging), sleeping and eating problems, poor eye contact, insensitivity to pain, hyper-/hypo-activity, and attention deficits.

One characteristic which is quite common in autism is the individual’s ‘insistence on sameness’ or ‘perseverative’ behavior. Many children become overly insistent on routines; if one is changed, even slightly, the child may become upset and tantrum. Some common examples are: drinking and/or eating the same food items at every meal, wearing certain clothing or insisting that others wear the same clothes, and going to school using the same route. One possible reason for ‘insistence on sameness’ may be the person’s inability to understand and cope with novel situations.

Autistic individuals sometimes have difficulty with the transition to puberty. Approximately 25% have seizures for the first time during puberty which may be due to hormonal changes. In addition, many behavior problems can become more frequent and more severe during this period. However, others experience puberty with relative ease.

In contrast to 20 years ago when many autistic individuals were institutionalized, there are now many flexible living arrangements. Usually, only the most severe individuals live in institutions. In adulthood, some people with autism live at home with their parents; some live in residential facilities; some live semi-independently (such as in a group home); and others live independently. There are autistic adults who graduate from college and receive graduate degrees; and some develop adult relationships and may marry. In the work environment, many autistic adults can be reliable and conscientious workers. Unfortunately, these individuals may have difficulty getting a job. Since many of them are socially awkward and may appear to be ‘eccentric’ or ‘different,’ they often have difficulty with the job interview.

Subgroups and Related Disorders

There is no adjective which can be used to describe every type of person with autism because there are many forms of this disorder. For example, some individuals are anti-social, some are asocial, and others are social. Some are aggressive toward themselves and/or aggressive toward others. Approximately half have little or no language, some repeat (or echo) words and/or phrases, and others may have normal language skills. Since there are no physiological tests at this time to determine whether a person has autism, the diagnosis of autism is given when an individual displays a number of characteristic behaviors.

In the last five years, research has shown that many people who engage in autistic behaviors have related but distinct disorders. These include Fragile X Syndrome, Landau-Kleffner Syndrome, Rett Syndrome, and Williams Syndrome.

Fragile X Syndrome is a form of mental retardation in which the long arm on the X chromosome is constricted. Approximately 15% of people with Fragile X Syndrome exhibit autistic behaviors. These behaviors include: delay in speech/language, hyperactivity, poor eye contact, and hand-flapping. The majority of these individuals function at a mild to moderate level. As they grow older, their unique physical facial features may become more prominent (e.g., elongated face and ears), and they may develop heart problems.

People with Landau-Kleffner Syndrome also exhibit many autistic behaviors, such as social withdrawal, insistence on sameness, and language problems. These individuals are often thought of as having ‘regressive’ autism because they appear to be normal until sometime between ages 3 and 7. They often have good language skills in early childhood but gradually lose their ability to talk. They also have abnormal brain wave patterns which can be diagnosed by analyzing their EEG pattern during an extended sleep period.

Rett Syndrome is a degenerative disorder which affects mostly females and usually develops between 1/2 to 1 1/2 years of age. Some of their characteristic behaviors include: loss of speech, repetitive hand-wringing, body rocking, and social with