What is Autism?

Autism is a complex developmental disability that typically appears during the first three years of life and is the result of a neurological disorder that affects the normal functioning of the brain. Autism spectrum disorders (ASDs) are a group of developmental disabilities characterized by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviors.

Autism can be associated with intellectual disability, difficulties in motor coordination and attention span, as well as with unique strengths and varying levels of impairment. The term ‘autism’ is often used to refer to all disorders within the autism spectrum, but in fact there are several different disorders under this umbrella term; each one has its own features and characteristics.

The exact cause or causes of autism are not yet known but it is believed that both genetic factors and environmental factors play a role in its development.

Early Symptoms of Autism

Some children with autism develop normally in early infancy, only to regress and lose acquired skills. That’s why it’s important to look for signs of autism as soon as possible for a better chance of getting an accurate diagnosis.

The earliest signs of autism can include:

• No babbling or pointing by age 1.
• No single words by 16 months (or no meaningful two-word phrases by 24 months).
• Loss of language or social skills at any age.
• Problems making eye contact, and not looking at objects that other people are talking about.
• Repetitive behaviors, such as flapping arms, rocking back and forth or spinning objects.
• Problems with sleeping and eating; resistance to cuddling or holding; unusual reactions to being touched, loud noises or bright lights

Autism’s genetic risk factors

The cause of autism is unknown. But some evidence indicates that it may be caused by more than one gene.

Autism seems to run in families. Children with an autistic older sibling have a 1-in-5 chance of developing the disorder, while children with an autistic parent have a 1-in-10 chance of developing it.

Autism may be linked to several genes, each of which contributes only a small amount to the overall risk of developing the disorder.

But scientists are discovering that different combinations of these genes can lead to autism in different people.

Autism’s environmental risk factors

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with a strong genetic component. However, several environmental factors have been identified as potential contributors to ASD risk. The purpose of this article is to review the evidence for these factors.

Environmental risk factors include exposure to viruses and other infectious agents, exposure to teratogens such as alcohol or valproic acid, and certain nutritional deficits during pregnancy. These are discussed below in addition to other possible environmental risk factors such as maternal stress, maternal obesity, maternal diabetes, and parental age at conception.

Virus-associated autism

The first indication that infections may play a role in the development of ASD came from epidemiological studies demonstrating an increased prevalence of ASD among children who had a sibling with ASD [1]. Subsequent research showed that children who had siblings with regressive autism were more likely to have had viral infections during infancy than those without regressive autism [2]. Although this finding was not consistent across all studies [3], it suggested that infection could be one factor contributing to ASD risk rather than being a consequence of ASD symptoms themselves.

Increased risk

Some studies have shown that if a mother has an infection during pregnancy, this may increase her child’s risk for developing autism spectrum disorders (ASDs). The most common infections include toxoplasma gondii and rubella virus. Some research also suggests that pregnant women who are infected with certain viruses are at increased risk for having a child with ASD.

It is believed that certain viral infections can damage a developing fetus’ brain cells during pregnancy or when they are first born, which could cause them to develop ASD later in childhood. In addition, some research suggests that certain viral infections may directly affect genes involved in ASDs.

Decreased risk

The biggest study of autism ever conducted has found that the condition is much more common than previously thought, with one in 68 children affected. But the study also found that some conditions known to be associated with autism — gastrointestinal disorders, epilepsy and attention-deficit hyperactivity disorder — are less common than expected.

The Centers for Disease Control and Prevention study looked at health and education records of 8-year-old children in 11 communities across the United States. It found that about 1 percent of children had been diagnosed with autism spectrum disorder (ASD). The rate is about 30 times higher than it was a decade ago, when the CDC estimated that just one in 150 children had ASD.

The new numbers could mean that early interventions can make a big difference in how well these kids do later on.

“There’s been a lot of research on what we call biomarkers — things like elevated levels of serotonin or low levels of cortisol,” says Dr. Deborah Hepburn, an assistant professor of psychiatry at Harvard Medical School who studies autism and other neurodevelopmental disorders. “That’s really important because those are things that might help us understand what causes autism.”

Differences in brain biology

About one in 68 children in the United States has an autism spectrum disorder (ASD), according to the Centers for Disease Control and Prevention. The disorder is characterized by social interaction, communication and behavioral challenges that can affect both speech and nonverbal behavior, such as eye contact, facial expressions and body language.

The genetic origins of autism have been traced to a range of genes that regulate brain development. Some of these genes may also be linked to other disorders such as attention deficit hyperactivity disorder (ADHD), schizophrenia or bipolar disorder, according to a 2018 study published in Nature Communications.

“Genes don’t operate on their own,” said Dr. Joseph Buxbaum, director of the Seaver Autism Center for Research and Treatment at Mount Sinai Hospital in New York City. “They do so within an environment where there are many other factors involved.”