Autism Symptoms: 8 Signs in Babies, Children, Teens & Adults

Updated in March 2024

Autism symptoms can vary from person to person, are not always easily perceived or visible. This condition ranges on a spectrum from mild to severe, and can present very differently in different patients. 

Symptoms are mostly related with difficulty communicating and socializing, and are often accompanied by uncommon behavior and interests. Some people with autism may have an excessive interest in specific topics or objects. They often have difficulty adapting to changes in routine and may exhibit abnormal body movements. 

Although some changes can be noticed in infancy, autism diagnosis is usually only confirmed much later in life. Symptoms that are mild may only be detected in adolescence or adulthood.

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Symptoms of autism

The most common symptoms of autism are:

1. Poor eye contact

Patients on the autism spectrum tend to have trouble maintaining eye contact when interacting with others. 

2. Difficulty expressing ideas and feelings 

Autistic people may have difficulty using and understanding body language, gestures and facial expressions. These patients often have trouble sharing their interests or feelings and demonstrating affection, which may be taken by indifference by others. 

3. Irritation with changes to routine

It is common for children with autism to have tantrums, to cry or to become aggressive with changes to routine or living environments. These changes may be small and not always obvious to caregivers. Small changes can trigger an emotional outburst,  like a change in the packaging of their favorite food or leaving the house and taking a different route to school.

4. Repetitive behaviors 

Behaviors may include flapping the arms, cracking knuckles, walking on tiptoes or rocking the body back and forth when standing or sitting. These behaviors may be seen as "habits" and are most common in times of high emotion. Other common behaviors include repeating specific words or phrases. 

5. More interest in objects than people

Children with autism generally prefer to play on their own, and have less interest in being with other children. They may have become irritated or aggressive when participating in group activities. They often present with a very strong interest for specific objects, toys or body parts. 

6. Sensitivity to sounds, lights, smells or contact 

Very lively or noisy environments, fireworks, flashing lights, strong smells, touch, or specific clothing can trigger an interest or an exaggerated emotional response (like crying or irritability). 

7. Not responding to their own name when called 

Children on the autism spectrum tend to ignore or overlook when their name is called. 

8. Difficulty communicating 

Communication difficulties among autistic patients may vary. Some may have had delays in talking as infants and others may have trouble starting or participating in a conversation. Many autistic patients may also have difficulty to new environments, and feel uncomfortable interacting with others. 

Suspecting autism 

Autism may be suspected in children who have delays in speaking, difficulty learning, trouble socializing or difficulty in becoming independent. These signs should be discussed with a pediatrician. 

When signs or symptoms are not identified in infancy, they may not be easily perceptible in adolescence or beyond. Therefore, if you suspect your teen may have autism. or if you notice signs in adulthood, you should consult a neurologist. 

Signs of autism in babies

At around 6 months, babies with autism may have less facial expressions, decreased eye contact and tend to smile less when interacting with others. By 9 months, the baby may not respond to interactions with their caregivers, not look when called, not babble sounds like "mama" or "papa", and not look to where an adult has pointed. By 12 months, the use of gestures or imitation, like waving, clapping or blowing a kiss may not be established. 

Read more about the most common signs of autism in babies

Signs of autism in children 

In mild cases of autism, symptoms may not be easily picked up as their are less obvious. Moderate to severe autism symptoms are more intense, and children generally present with learning difficulties, trouble interacting with other children, and difficulty with independent tasks. 

Autism symptoms in children may include: 

1. Difficulty with social interactions 

  • Avoiding eye contact
  • Not smiling when others smile at him/her, or little smiling in general 
  • Not allowing hugging or kissing 
  • Difficulty making friends
  • Difficulty relating to other children and a preference for being alone

2. Difficulty communicating 

  • Not speaking as much as other children 
  • Repeating specific words or phrases many times 
  • Not understanding other people’s facial expression or gestures 
  • Not understanding a joke, pun or sarcasm 
  • Not responding to their own name, or taking a long time to respond 
  • Monotone, robotic voice

3. Behavioral changes

  • Not sensing fear in dangerous situations, like crossing a street without looking and wanting to interact with dangerous animals 
  • Becoming agitated or irritated with small changes to routine
  • Developing an interest for something specific, like a toy car wheel or plane wing 
  • Repetitive movements, like clapping, shaking the fingers or rocking the body back and forth 
  • Becoming very agitated in public or noisy environments 

In addition, autism can present very different in girls. They may be more quiet or have more trouble adapting to social situations. In any way, you should consult a pediatrician if you suspect your child may have autism. 

Signs of autism in teens and adults 

Sometimes, signs and symptoms may be unnoticed in childhood and may become more pronounced in adolescence or adulthood. These periods of life require larger responsibility and independence in terms of school or work, which may make symptoms more visible.

The main symptoms of autism in teens and adults are:  

  • Difficulty making friends and preferring to be alone
  • Avoiding eye contact
  • Becoming anxious during social interactions
  • Being rude, blunt or uninterested in what others are saying
  • Presenting with symptoms of depression and anxiety 
  • Liking to plan things very carefully and cautiously 
  • Not understanding other people’s feelings 
  • Picking up on small details, like smells, sounds or patterns
  • Becoming agitated with changes to routines or habits 
  • Discomfort with close proximity or touch
  • Having an excessive interest for uncommon topics (like astronomy) or specific activities (like watching several news channels), or wanting to know all the specific details of one topic 

An autism diagnosis during this life stage can be very difficult, as symptoms may be mild, or the patient may have developed coping mechanisms to manage their symptoms (e.g. avoiding uncomfortable situations), which ends up masking them. 

Treatment options

There is no specific treatment for autism, and interventions depend on the severity of symptoms. Treatment approaches are aimed at improving communication techniques, concentration and overall quality of life. Treatment can be provided by a team of health care professionals, like doctors, physiotherapists, speech therapists and psychologists, and depends on the health needs and goals of each patient. Medications may be prescribed to manage specific symptoms.