ASD, Early Signs, & Possible Causes

Autism spectrum disorder (ASD), a developmental condition that affects social interaction, behavior, and verbal skills, affected 1 in 54 8-year-old children as of 2016, the most recent year in which the Autism and Developmental Disabilities Monitoring Network of the Centers for Disease Control and Prevention's (CDC) tracked data. This was up substantially from the network’s first surveillance year of 2000 in which only 1 in 150 8-year-old children showed symptoms.

The most common symptoms of ASD are repetitive behaviors and challenges communicating verbally and nonverbally with others. Some people diagnosed with ASD may have issues with spoken language, maintaining eye contact, and understanding the appropriate tone of voice, facial expressions, and gestures. Repetitive behaviors may involve body movements such as spinning, rocking, or flapping, or performing the same motions with objects, for example, flipping levers or spinning wheels.

Other known ASD symptoms include obsessive interest in particular topics, resistance to change or an unwavering desire for routine and structure, ritualistic behaviors, and being anxious or overwhelmed in social situations. People with ASD also may have difficulty recognizing their and other people's emotions.

Determining ASD in a child can be difficult. Some infants exhibit symptoms during their first few months, while others do not show signs until 2 or 3 years old. Conversely, some children without ASD show some of the aforementioned symptoms early in their development.

At 6 months, a child may be at risk for ASD if he or she avoids eye contact or has yet to show big smiles or joyful expressions. By 12 months, children with ASD are unlikely to engage in babbling and rarely point, reach, or wave. They also may not respond to their name. If they are not speaking an appropriate amount at the 16- and 24-month marks, they should be taken to a pediatrician for a professional evaluation.

Parents who are unsure if their child has ASD can complete the Modified Checklist for Autism in Toddlers. This online screening questionnaire, compiled by Autism Speaks, includes questions such as, "If you point at something across the room, does your child look at it?" and "Does your child make unusual finger movements near his or her eyes?"

Professionals diagnose ASD and the level of severity by following guidelines in the fifth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders. There are three levels of severity, with the third requiring that the child receives substantial support during development. However, early diagnosis and intervention can help improve ASD-associated conditions.

Because of the complexity of the condition and its range of symptoms, researchers have been unable to attribute specific causes of ASD. Inherited and spontaneous genetic mutations may affect brain development and impact the severity of symptoms. Researchers also are exploring the impact of environmental factors, such as viral infections, air pollutants, and complications during pregnancy. Children are at a higher risk of ASD if it is present in their family history or they were born before 26 weeks of gestation. Additionally, boys are four times more likely to be diagnosed with ASD than girls.