Understanding Autism
Spectrum Disorder

A Developmental Disorder


Autism spectrum disorder (ASD) is a developmental disorder marked by impaired social interaction, limited communication, behavioral challenges, and a limited range of activities and interests. In 2021, the CDC reported that 1 in 44 children in the US is diagnosed with ASD. It is more common in boys than girls (1 in 27 boys, 1 in 116 girls). 

Individuals with ASD can show a wide variety of behavioral symptoms, from failure to develop appropriate peer relationships to a delay in or a total lack of spoken language. For individuals who do speak, there may be a repetitive use of language or a delay in the ability to sustain a conversation with others. Symptoms of autism can also include hyperactivity, short attention span, impulsivity, aggressiveness, self-injurious behavior, and temper tantrums.

Evidence-based autism treatment promotes the development of social and communication skills and minimizes behaviors that interfere with functioning and learning. Intensive, sustained, evidence-based autism treatment can increase an individual’s ability to acquire language, learn, function in the community, and fulfill his/her potential. The Diagnostic and Statistical Manual of Mental Disorders is the most widely accepted reference used for the classification and diagnosis of ASD. The most recent edition (DSM-5; American Psychiatric Association, 2013), redefined the diagnostic criteria for ASD, which was previously regarded as three distinct diagnoses (i.e., autistic disorder, pervasive developmental disorder—not otherwise specified, and Asperger’s disorder). The DSM-5, however, classifies ASD as a single disorder characterized by persistent deficits in social communication and social interaction, in addition to restricted, repetitive patterns of behavior, interests, or activities.

Signs And Symptoms

The presentation and severity of symptoms vary widely among individuals with ASD. Early signs of ASD may be observed in an infant as young as 6 months old. Some common signs and symptoms of ASD include:

  • Lack of eye contact
  • Not responding appropriately to greetings
  • Difficulty initiating and maintaining conversations with others
  • Not responding appropriately to others’ gestures and facial expressions
  • Difficulty using gestures and facial expressions appropriately
  • Appearing to be unaware of others’ feelings
  • Not engaging in pretend play
  • Preferring to play alone
  • Repeating sounds, words, or phrases out of context
  • Becoming distressed by minor changes in routines
  • Performing repetitive movements, such as hand–flapping or rocking
  • Playing with toys in unusual ways, e.g., spinning them or lining them up
  • Having unusually strong attachments to particular objects
  • Limiting conversations to very specific topics
  • Exhibiting oversensitivity to sounds or textures
  • Appearing to be indifferent to pain
  • Experiencing delays or plateaus in skill development
  • Losing previously acquired skills
  • Displaying challenging behaviors, such as aggression, tantrums, and self-injury

The Modified Checklist for Autism in Toddlers, Revised (M-CHAT-R) is a free, validated screening tool that assesses an individual’s risk for ASD. If you have concerns about your child’s development, express your concerns immediately to your child’s pediatrician and request a referral to a specialist who can perform more thorough assessments. 


The factors contributing to increases in reported rates of ASD are not fully understood. While increased rates may be partially explained by improved screening and diagnostic practices, researchers are also exploring the roles of various environmental and genetic risk factors. The prevalence of ASD has increased more than 150% since 2000. CDC statistics reveal that ASD is present across all races, ethnicities, and socioeconomic groups. In addition, boys are more likely to develop ASD than girls.

Risk Factors

There is no single known cause for ASD. Rather, evidence suggests that there are many factors involved in the development of ASD. Researchers are actively exploring the roles of various genetic and environmental risk factors.

Genetics have been found to play a significant role in the development of ASD. Evidence indicates that siblings of individuals with ASD are at an increased risk of developing ASD themselves. Research conducted on twins has found genetics to play a sizable role in the development of ASD. Additionally, rates of ASD are higher among individuals with various genetic disorders, including fragile X syndrome and tuberous sclerosis. Numerous gene mutations have been found to increase the risk of developing ASD by varying degrees. Sometimes, gene mutations are inherited from a parent who carries the same gene mutation other times gene mutations occur spontaneously. Advanced parental age, another risk factor for ASD, may increase the chance of genetic mutations that occur spontaneously as genetic material is copied over from parent to offspring.

In addition to genetic factors, a number of environmental factors have been found to increase the risk of developing ASD. Many environmental risk factors consist of prenatal exposures, including maternal contact with high levels of air pollutionmaternal viral and bacterial infections and maternal ingestion of some prescription drugs including selective serotonin reuptake inhibitors, a type of antidepressant. On the other hand, prenatal vitamins ingested during pregnancy and the months preceding pregnancy have been found to reduce the risk of ASD. Birth complications involving oxygen deprivation are also associated with an increased risk of ASD.


Intensive behavioral intervention (IBI) using the principles and procedures of applied behavior analysis (ABA) is the only empirically validated treatment for ASD. ABA is conducted at a high intensity, typically between 30 and 40 hours per week, for multiple years. Evidence suggests that greater treatment intensity leads to superior outcomes. Evidence also indicates that ABA is more effective if initiated in early development; however, services initiated at any age are beneficial for the acquisition of valuable skills.