Common Symptoms and Signs of Autism

Symptoms vary among individuals with autism spectrum disorder, also commonly referred to as ASD, or just autism, the neurological and developmental disorder that can cause problems with communication, social skills, and other behaviors.

Whether or not certain problems occur can depend on the individual and the severity of the disorder. Symptoms can also appear at different ages for some compared with others, but in most cases symptoms of autism start to show up before age 3. (1)

Here are some of the warning signs to be on the lookout for that could indicate someone has autism. Note that the warning signs and symptoms are different for young children, older children, and adults — who may have autism, but whose disorder may have been ignored or misdiagnosed earlier in life.

Symptoms of autism in babies and toddlers are usually delays in learning, developing language, and communication skills, or behavioral problems. Common early warning signs are difficulty responding to one’s name when they are addressed and lack of eye contact, explains Thomas Frazier, PhD, professor of psychology at John Carroll University in Ohio and board member of Autism Speaks, an autism advocacy organization.

Another indication to look for early on is babies and young children failing to join in a shared experience, such as observing an object or an event that everyone around them is paying attention to, Dr. Frazier says. For instance, if you take your child to the zoo and he looks at a lion you are pointing to, but doesn’t necessarily look back at you to acknowledge what he’s looking at and doesn’t share in the joint experience of the moment.

Children who have an autism spectrum disorder might also display very specific, sometimes intense, interests in subjects that others might not, adds Jeremy Veenstra-Vanderweele, MD, director of child and adolescent psychiatry at Columbia University College of Physicians and Surgeons in New York City. In a conversation, a child with autism might return, intently, to one topic over and over. That was the case for one child Dr. Veenstra-Vanderweele worked with who had a very strong interest in sharks and did not talk about any other topic.

Repetitive behaviors or following the same patterns over and over can also be indicative of an autism spectrum disorder.

“A lot of these kids display ritualistic behaviors. Certain things have to happen the same way each time,” Veenstra-Vanderweele says. “They might only feel comfortable in your car going the same way to school every day, for instance.”

Other signs that could indicate a baby or toddler has autism include: (2)

• Either not smiling at others or making eye contact by about 6 months
• Not making vocal sounds or other nonverbal communication by 6 months
• Not beginning to babble, use gestures to communicate, or responding to their name when called by age 1
• Not speaking any words by about 16 months
• Not speaking in phrases by age 2
• Losing previously acquired speech, communication, or social skills

Other potential signs of autism at any age include:

• Avoiding eye contact or preferring to be alone
• Struggling to understand others’ feelings
• Not speaking or having trouble developing language skills
• Repeating words or phrases over and over
• Getting upset by minor changes in one’s routine or surroundings
• Having limited interests
• Performing repetitive behaviors or gestures
• Having unusual or intense reactions to sounds, smells, tastes, textures, lights, or colors

It’s important to note that not all children with autism will exhibit all of these behaviors. And some children will start showing signs of the disorder later than others. For instance, children with the rare childhood disintegrative disorder (CDD), or “Heller’s syndrome,” develop normally until age 3 or 4, and then start to lose motor, language, social and other skills they have already learned. (3)

This disorder was reclassified to be on the spectrum of autism disorders, according to the most recent version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association in 2013. (4)

Some individuals with autism fall on the high-functioning end of the spectrum. These individuals typically have very high levels of intelligence and don’t tend to have trouble with language, but they may struggle with social skills, exhibit repetitive behaviors, and have limited interests.

This diagnosis was previously considered Asperger’s syndrome, but is now considered to be a disorder on the autism spectrum, according to the 2013 DSM-5. (5)

Some of the behaviors to look for include:

• Having limited or inappropriate social interactions
• Speaking in repetitive or “robotic” patterns
• Challenges with nonverbal communication, such as gestures and facial expressions, but having no problems or above-average verbal skills
• Having a tendency to discuss oneself rather than others
• The inability to understand social or emotional issues
• Lack of eye contact during conversation
• Inability to reciprocate in a conversation
• Showing an obsession with specific (and oftentimes unusual) topics
• Having one-sided conversations
• Having awkward moments or mannerisms

It’s important to note not everyone with the condition will have all of these problems, and some may experience the problems to greater degrees than others.

It’s not unusual for this type of autism to be diagnosed later in adolescence or adulthood, because some of the telltale signs of the disorder aren’t apparent until the individual is in an environment where they would be more noticeable, such as in a school or office setting.

Autism is 4.5 times more common among boys than girls. But it’s important to realize that autism symptoms differ in boys and girls, and some recent research suggests that lack of understanding of the differences may have left many girls with autism misdiagnosed and undertreated.

One study that looked at girls and boys who met ASD criteria and compared them with those who individuals who were screened for autism, but not diagnosed, found that the girls with autism displayed more severe symptoms when it came to intellectual level and behavioral difficulties, yet similar scores to their peers who were not diagnosed with autism when it came to other criteria used for diagnosis. (6) The research suggests that girls with milder autism may go undetected by current tests used to identify the disorder.

Another 2017 study suggested that emotional and behavioral symptoms may be more prominent in girls with autism than boys, and that repetitive and restrictive behavior symptoms may be more common in boys with the disorder. (7) And a 2015 study found that there may be biological differences in the brains of girls with autism compared with boys with the disorder.

“Autism has primarily been studied from the viewpoint of boys with the disorder,” Vinod Menon, PhD, professor of psychiatry and behavioral sciences at Stanford University School of Medicine in California and senior author of the 2015 study, said in a press release when the research was first published. “Understanding gender differences can help in identifying the behavioral skills that are most important to remediate in girls vis-à-vis boys.”

Autism does not develop in adulthood, but in some cases the disorder is misdiagnosed or not diagnosed in childhood. People who are now adults grew up in a time when autism was less understood and studied, and early warning signs may have been ignored. (8,9) Getting an accurate autism diagnosis as an adult can be helpful.

Still, the disease can be difficult to diagnose in previously undiagnosed adults, because autism is so variable and may affect people in different ways over time, explains Veenstra-Vanderweele. There are no specific criteria doctors can use to diagnose autism in adults, but healthcare providers might ask whether you’ve experienced challenges in social interactions at home, at school, or at work, and whether you can remember specific learning challenges at a young age that are typical in autism. (10)

And if you are an adult with undiagnosed autism who has attended school, potentially held a job, and independently navigated social situations, there is a high chance that you have developed resources of your own to cope in the world without treatment of any kind.