Autism Spectrum Disorder: Symptoms and Diagnosis

Does your child avoid eye contact? Does the vacuum cleaner make him scream and cry? Here’s how you can tell whether these are signs and symptoms of autism spectrum disorder (ASD).

One study found that children with ADHD are up to 20 times more likely to exhibit some signs of Autism Spectrum Disorder (ASD) than are their neurotypical peers1. Autism is generally characterized by social and communication difficulties, and by repetitive behaviors. Because it occurs alongside other conditions that can cause social difficulties, it’s important to separate social difficulties that mimic autism, but that aren’t autism, from actual pragmatic differences. Early detection and treatment of the correct condition are crucial.

Signs and Symptoms of ASD in Children

More severe forms of autism are often diagnosed in the first two years of a child’s life, but less severe forms may be diagnosed later when developmental delays become apparent. Children with ASD often exhibit problems with social interactions, trouble with verbal and nonverbal communication, and stereotyped (repetitive or ritualistic) behaviors. Symptoms fall in a range, or spectrum, and vary in their severity in these three main areas. People with autism can be high functioning and have milder challenges, or they can have more severe impairments, like impaired spoken language, that interfere with everyday life. Children with autism don’t intuitively grasp the social world, and their social skills may lag behind those of other children. This becomes evident during play and communication. They have limited imaginative play skills, take things literally, and may not use gestures to communicate. As they get older, they may learn these skills, but still have autism. Common symptoms include:

Social Symptoms

  • Does not respond to name consistently when called (in infancy)
  • Tendency to avoid eye contact (in infancy)
  • Difficulty imitating the actions of others (in toddlerhood)
  • Delays in imaginative play (in toddlerhood)
  • Preference for solitary play (in toddlerhood)
  • Limited back and forth play or interactions (in toddlerhood)
  • Difficulty seeing things from another person’s perspective
  • Failure to respond to social cues
  • Trouble understanding the perspective of others

Language Symptoms

  • Delayed speech language abilities/babbling (in infancy)
  • Delays in using gestures to communicate (in toddlerhood)
  • Difficulty understanding body language
  • Trouble creating sentences
  • Tendency to repeat words or phrases

Behavioral Symptoms

  • Failure to seek comfort when upset (in toddlerhood)
  • Frequent emotional outbursts or physical aggression

Common repetitive behaviors include:

  • Rocking
  • Twirling
  • Arranging objects in a particular order
  • Wiggling fingers
  • Flapping hands
  • Atypically intense or unusual interests

Symptoms may look different in girls and boys – and that disparity may delay diagnosis for some girls with the condition. Girls are diagnosed later than boys with conditions previously known as pervasive developmental disorder (PDD) and Asperger’s syndrome – both forms of ASD that are now classified as “high-functioning autism” in the current Diagnostic and Statistical Manual of Mental Disorders2. Additionally, the symptoms that lead to a diagnosis vary by gender. Young girls more commonly have trouble with social cues, while boys exhibit repetitive behavior like hand flapping. In older children, ages 10-15, boys have more social issues than do girls. ASD symptoms in girls may be more nuanced and difficult to notice, leading to delayed – or completely missed — diagnosis3.

Medical professionals agree that starting treatment as soon as possible is vital to enhance the child’s ability to communicate and develop coping skills with intensive Early Intervention programs.

Signs and Symptoms of ASD in Adults

ASD is typically a lifelong condition, though a small percentage of children outgrow the diagnosis9. Therapy, started even late in life, may have major benefits. Symptoms of ASD in adults include:

  • Difficulty interpreting what others are thinking or feeling
  • Trouble interpreting facial expressions, body language, or social cues
  • Difficulty regulating emotion
  • Trouble keeping up a conversation
  • Inflection that does not reflect feelings

Adults can exhibit repetitive behaviors and have specific, extreme interest in a particular topic like sports teams or science. These interests may border on obsessions.


There isn’t a lab test to diagnose ASD—symptoms are extremely broad and unique to each individual. Because some symptoms overlap with ADHD, diagnosing and separating the disorders can be difficult. Diagnosing ASD requires an autism-specific behavior evaluation conducted by a qualified professional like a developmental pediatrician, psychiatrist, or neurologist.

First, physicians will screen for symptoms that indicate ASD, using a diagnostic tool. The Modified Checklist of Autism in Toddlers (M-CHAT) and its series of informative questions can indicate if a child should be evaluated. Then, the physician will likely observe you or your child and talk to you about development, social interaction, and communication skills. Additional diagnostic tools include the Screening Tool for Autism in Two-Year-Olds (STAT), the Social Communication Questionnaire (SCQ) for children four years of age and older4. For high-functioning autism the common screeners are the Autism Spectrum Screening Questionnaire (ASSQ), the Childhood Asperger Syndrome Test (CAST), and the Australian Scale for Asperger’s Syndrome4.

If the screening tools indicate ASD, a diagnostic evaluation involving a psychologist, neurologist, speech therapists, and other professionals who are experts in ASD will begin. Typically, it will involve genetic testing, neurologic exams, and interviews with caregivers that may use the Autism Diagnosis Interview-Revised (ADI-R) or the Autism Diagnostic Observation Schedule (ADOS-G)4. Children should also be evaluated for other conditions like hearing disorders, which could be causing similar symptoms.

Most insurance companies, and virtually all public schools, require a written evaluation by a specialist before they will provide, or pay for, the services autistic children need. Because autism cannot be diagnosed with a simple medical test, screening and diagnosis are usually lengthy and expensive, involving interviews, observation, and evaluations. A doctor, psychologist, language pathologist, and occupational therapist are usually consulted. Physicians will screen to rule out other disorders that might cause difficulties. Even when a professional ventures an opinion, he will often hedge by saying, “He is quirky and has some typical behaviors, and they are somewhat consistent with a diagnosis of a high-functioning autism.” This kind of talk is frustrating, but it’s sometimes unavoidable. Evaluating the child at a later date often clarifies things. Sometimes a child doesn’t need a diagnosis, as long as he is getting the help he needs.

For adults and adolescents, a diagnosis may provide relief as it explains why they have struggled in certain areas. Learn more about treatment for ASD.

1 Dennis Thompson. “More Links Seen Between Autism, ADHD.” HealthDay. (2013). Web. (

2Mark Bertin. “Autism and ADHD: The Complete Playbook for Social Challenges.” ADDitude Magazine. (2015). Web. (

3Janice Rodden. “New Study: Autism – Like ADHD – Diagnosed Later in Girls.” ADDitude Magazine. (2015). Web. (

4National Institute of Mental Health. “How Autism is Diagnosed.” PsychCentral. (2013). Web. (

TAGS: Comorbid Conditions with ADD

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