Autism Signs, Symptoms, and Statistics

Autism, also called Autism Spectrum Disorder (ASD), is a group of complex neurological disorders characterized by problems with nonverbal communication, speech, repetitive behaviors and social skills. These problems are severe enough to interfere with daily life and are persistent over time.  People with autism are often unusually sensitive--or insensitive--to stimuli. 


Autism affects 1 in 59 children in the US alone. Autism is classified as a spectrum disorder, a condition with a range of severity, from mild to severe, as well as a group of linked conditions believed to be caused by similar mechanisms. 

There is no one monolithic kind of autism. It has many subtypes and levels of severity. Autism is also associated with high rates of certain physical and mental health conditions.


Autism develops in early childhood, although it may not be diagnosed until later. It’s possible for infants less than 18 months old to display predictive signs of autism, although some children with autism show no symptoms as infants. A screening tool, the Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F) is a questionnaire parent may use to assess their children for the risk of autism. Autism can be accurately diagnosed as young as two years old

Diagnosing Autism

The Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R™) is a checklist of common autism traits and behaviors.

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Signs of Autism in Infants and Toddlers

  • Little eye contact
  • No two-way interaction with adults or others
  • No smiling
  • Little or no babbling, pointing, or meaningful gestures by 12 months
  • No one-word communications by 16 months
  • No two-word phrases by 24 months
  • Unresponsive to sounds, voices, or hearing their name called
  • Little to no social interaction with other children

Signs of Autism in Teens and Adults

  • Difficulty interpreting social cues, the emotions of others, facial expressions, and non-verbal cues
  • Emotional dysregulation 
  • Trouble following and participating in conversation
  • Inappropriate affect
  • Repetitive behaviors
  • Insistence on an unvarying routine
  • High levels of inflexibility
  • Insistence on strict adherence to daily routines, with meltdowns when changes happen
  • Thorough, profound knowledge of a favored topic, with a borderline obsessional fascination with it.

Autism Differences in Gender

There are distinct differences between males and females in the number of diagnosed cases of autism. For every female diagnosed, four males are identified with autism. There is emerging evidence that girls display different behavioral symptoms of autism than boys, which may account for the uneven gender distribution.

Types of Autism Spectrum Disorders

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Autism Spectrum Disorder

People with autism have unusual, repetitive behaviors, problems communicating, delayed language development, and significant problems with social interaction. It’s common for people with autism to have intellectual disabilities. Autism is diagnosed in childhood, with many people being diagnosed before the age of 4, although the signs of autism can be seen in children as young as 18 months.

Asperger Syndrome

Asperger Syndrome (AS) is often thought described as of as a mild form of high-functioning autism (HFA). Named by Dr. Hans Asperger in the 1940s, Asperger Syndrome is noted by a lack of significant problems with language development and profound, even obsessional, focus on certain subjects. People with AS are often not diagnosed until adulthood.

Pervasive Developmental Disorder - Not Otherwise Specified

Atypical autism, or PPD-NOS, includes a mix of autism and Asperger’s symptoms but not every classic symptom. Symptoms tend to be mild and cause communication and social interaction problems only.


Called “atypical autism,” PDD-NOS involves a person showing some signs of autistic disorder or Asperger’s, but not all of the classic symptoms of either condition.. This is sometimes called “atypical autism,” or PDD-NOS. People who meet some of the criteria for autistic disorder or Asperger syndrome, but not all, may be diagnosed with atypical autism. These people usually have fewer and milder symptoms than those with autistic disorder. The symptoms might cause only social and communication challenges.

Autism vs. Asperger Syndrome

Many repetitive behaviors people with autism perform are a kind of self-stimulation, hence called “stimming.” Stimming behaviors are comforting and a way people with autism control their anxiety.


  • Repetitive behaviors. Repetitive behaviors like hand flapping, rocking back and forth, spinning and toe walking are common. 
  • Staring at objects, especially if they are moving.
  • Ritualistic behaviors, like touching objects in a fixed, particular order, line up objects, and stacking items on top of each other.
  • Highly focused interest in favorite topics, including encyclopedic knowledge about that topic.
  • Strong need for an unchanging daily routine with well-defined boundaries, such as an unvarying daily routine, eating the same food and the same portion sizes daily, same clothing, and so forth.
  • Highly resistant to change or unexpected variations in routine.


Food and Gastrointestinal Issues. People with autism are unusually sensitive to the taste, smell, appearance and texture of foods.They may enjoy a very narrow range of food selections and be comfortable eating exactly the same thing every day. Children with autism avoid fruits and vegetables and will shun them if possible, preferring starchy foods high in sugar and carbohydrates. The strong tastes associated with fruits and vegetables are thought to be part of this taste aversion. 


Gastrointestinal issues are a big part of life for people with autism. Constipation, diarrhea, and stomach pain occur with greater frequency in people with autism


Autism Meltdown. An autistic meltdown isn’t the same thing as a temper tantrum. Children who throw a tantrum typically are wanting something, whether it’s a toy, food, or attention. When a child throwing a tantrum gets their way, they calm down. A meltdown is a loss of control usually caused by an overload of sensory information. An autistic meltdown can occur at any age.


Autism and Sensory Overload. People with autism have unusually sensitive sensory systems, which causes them to be easily overwhelmed by sounds, sights, noises, and even the texture of surfaces. It can be very hard for them to ignore or tune out annoying sensory input. Sensory overload can easily lead to a meltdown.


The following are just a few examples of sensory stimuli that can be overwhelming to a person with autism:

  • Buzzing or flickering fluorescent lights
  • Droning noises, like lawnmowers, leaf blowers,
  • Odors like perfume, wall paint, chemical scents like carpet cleaners, fabrics, or fumes
  • Slippery textures (which textures are distressing vary from person to person)
  • Whispery sounds like the rustling of leaves
  • A sudden change from a calm, quiet environment into a brighter, more noisy environment
  • Crowd noise

Autistic Savant. Savantism is an unusually high level of ability at a skill that’s demonstrated without study or practice. Examples of savantism include:


  • The ability to memorize books by flipping through the pages and demonstrate total recall.
  • Performing complex mathematical calculations in their head
  • Prodigious musical talent upon first learning an instrument
  • Immediate foreign language acquisition


Most savants are not autistic. However, ten percent of people with ASD are savants, as opposed to 1 percent in the general population. Savants display abilities that seem supernatural or superhuman, but savants with autism will have trouble with language development and all the other issues associated with autism.