Understanding Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that emerges in early childhood. At this time, no physical tests are available to diagnose ASD. Diagnoses may be provided by licensed psychologists or medical doctors and are based on a child’s developmental history and observable behavior. While ASD can be reliably diagnosed as early as 18 to 24 months, most children, unfortunately, are not diagnosed until after 4-years-old.

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.

  • Avoids making eye contact
  • Does not respond appropriately to greetings
  • Has trouble initiating and maintaining conversations with others
  • Does not respond appropriately to others’ gestures and facial expressions
  • Has difficulty using gestures and facial expressions appropriately
  • Appears to be unaware of others’ feelings
  • Does not engage in pretend play
  • Prefers playing alone
  • Repeats sounds, words, or phrases out of context
  • Becomes distressed by minor changes in routines
  • Performs repetitive movements, such as hand flapping or rocking
  • Plays with toys in unusual ways, for instance spinning them or lining them up
  • Has unusually strong attachments to particular objects
  • Limits conversations to very specific topics
  • Exhibits over-sensitivity to sounds or textures
  • Appears to be indifferent to pain
  • Has delays or plateaus in skill development
  • Has lost previously acquired skills
  • Displays 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 a child’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 Centers for Disease Control and Prevention (CDC) estimates that 1 in 68 children are diagnosed with ASD in the United States. That is about 30% higher than the previously estimated rate of 1 in 88 reported in 2012. 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. CDC statistics reveal that ASD is present across all races, ethnicities, and socioeconomic groups. In addition, boys are nearly 5 times 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 children 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 children 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 while 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 pollution, maternal 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) is the only empirically validated treatment for ASD. Based on the principles of applied behavior analysis (ABA), IBI is conducted at a high intensity, typically between 20 and 40 hours per week, for multiple years. Evidence suggests that greater treatment intensity leads to superior outcomes. Evidence also indicates that IBI is more effective if initiated in early development; however, services initiated at any age are beneficial for the acquisition of valuable skills.