Signs of autism

What is autism?

Autism, or autism spectrum disorder (ASD), is a developmental disorder. It affects how people communicate and interact with others, as well as how they behave and learn.[1]

Autism is a lifelong condition and signs can appear when a person is very young. Autism cannot be cured but therapies and support services can help a person with autism improve symptoms.

What is a spectrum disorder?

Autism is a spectrum disorder, which means that people can experience a wide range of symptoms and of varying severities. For example, a person with autism who is towards the high functioning range of the spectrum will have a good grasp of language, but a person towards the low functioning range of the spectrum may not speak at all.[2]

As such, it is important to note that a person with autism spectrum disorder will not display all symptoms and symptoms will vary in severity. However, a person with autism will display several of these behaviors and symptoms.

Signs and symptoms of autism

There are many signs and symptoms that could indicate a person has autism spectrum disorder. Not all children with autism will have every symptom, and some children without autism may display some of the same behaviors and symptoms.

People with autism spectrum disorder often have difficulties with communicating, and connecting emotionally and socially with others. They may also process sensory information, such as sounds and smells, differently from other people. These differences can underlay some of the behavioral signs of autism that people may display.[3][4]

When looking for early signs of autism spectrum disorder, there are developmental milestones that children are expected to reach by certain ages, such as babbling by four months old and being able to use simple sentences by two years old. If a child reaches these milestones later, or does not develop the skills at all, it may indicate a developmental disorder such as autism spectrum disorder.[5]

Autism can be diagnosed by two years old, though symptoms may be apparent much earlier.

Common signs of autism

Some of the more common signs that may indicate a person has autism include:[6]

  • Avoiding eye contact
  • Delayed speech and communication skills
  • Not responding to their name by 12 months
  • Not pointing at distant objects by 14 months
  • Being upset by relatively minor changes
  • Unexpected reactions to sounds, tastes and smells
  • Focusing on or becoming obsessed by particular interests or objects
  • Engaging in repetitive behavior such as flapping hands or rocking

Signs of autism in babies

Autism spectrum disorder is a developmental disorder, which means that signs become apparent as a child does not develop as expected, for example developing speech or learning to crawl later than expected.

As such, there are few signs of autism that are noticeable in newborns. However, if a baby fails to reach developmental milestones expected at two months old, four months old, six months old, nine months old and a year old, this could be a sign of autism or another developmental condition.[5]

Good to know: Not all babies reach developmental milestones at the exact same time. It is normal to have some variation in development. If in doubt about how well a child is developing, check with a doctor.

Some of the early signs that a baby under one year old may have autism spectrum disorder include:[6][7][8]

  • Not babbling by four months old
  • Not smiling by five months old
  • Not laughing by six months old
  • No interest in games like pat-a-cake or peek-a-boo by eight months old
  • Not responding to their name by 12 months old
  • Not looking at objects pointed out by other people by 12 months old
  • Being upset by loud noises
  • Looking to a parent for comfort in new situations
  • Being happy to play alone for long periods of time
  • Not making eye contact

Signs of autism in toddlers

Some of the signs that a toddler, between one year old and two years old, may have autism spectrum disorder include:[9]

  • Not developing language skills such as saying mama or dada by one year old, or using simple sentences by two years old
  • Only saying one word at a time
  • Repeating words over and over
  • Lacking interest in playing social games or being around other children
  • Not making eye contact
  • Not imitating others
  • Engaging in repetitive behavior such as flapping hands, rocking or twirling

Around 25 to 30 percent of children with autism have developed some language skills by 18 months but then go on to lose them. Some children between one year old and two years old may also lose play or other social skills they have developed.[6][10]

Signs of autism in young children

Symptoms of autism spectrum disorder are usually clear by two or three years old. The range of behaviours and skills covered here may become apparent between two years old and five years old.

Some signs that a child has autism spectrum disorder may include:[9][11][12][13]

  • Not expressing emotion or only a limited range of emotions
  • Difficulty interpreting different emotions in others
  • Not seeming attached to parents
  • Lacking interest in playing social games or the company of other children
  • Interest in playing with one particular toy or object
  • Echolalia, repeating other people’s words or phrases
  • Repeating own words over and over
  • Using formal language rather than the slang of their peers
  • Not developing language skills at all
  • Difficulty toilet training
  • Having tantrums or meltdowns
  • Physically aggressive behaviour
  • Challenging behaviour, such as banging head on wall or picking at skin
  • Engages in behavior such as flapping hands, rocking or twirling

Children with autism spectrum disorder have difficulty interpreting what other people are thinking and feeling, and often miss social cues. A child with autism may not be able to tell the difference between an adult who says “come here” while happy and smiling, and an adult who says “come here” while angry and frowning. This can be confusing and creates the impression the child is not connecting with people.[11]

Good to know: Echolalia is a normal part of many children’s language development and generally goes away by around three years old. Children with autism are more likely to persist with echolalia as they get older.[14]

Signs of autism in older children and teenagers

Although autism spectrum disorder can reliably be diagnosed from the age of two or three years old, many children do not receive a diagnosis until they are older. Milder symptoms in children with autism spectrum disorder who are higher functioning may not be recognized until they are in school.

Autism is a spectrum condition, which means that children will have different experiences of day-to-day living. Children who are more than five years old and on into their teenage years, who have mild symptoms and are towards the higher functioning range of the autism spectrum, may:[6][13][15][16]

  • Develop a narrow range of interests or obsessions with certain topics
  • Engage in repetitive behavior such as hand flapping, twirling or snapping a rubber band
  • Not make eye contact
  • Have difficulty with social interactions
  • Not understand emotions in others or themselves
  • Prefer to be on their own
  • Avoid physical contact
  • Have unusual sleeping patterns
  • Use formal language rather than the slang of their peers
  • Place great importance on routines and rules
  • Develop strong preferences for certain foods, clothes or objects

Children who have more severe symptoms and are towards the lower functioning range of the autism spectrum may:[6][13][15][16]

  • Not use speech at all
  • Become extremely distressed at changes to routine
  • Exhibit challenging behavior, such as being aggressive or banging head on wall
  • Need assistance with everyday living, such as bathing and dressing
  • Engage in repetitive behaviors, such as rocking
  • Insist on rules and routine
  • Develop rigid preferences for certain foods, clothes or objects
  • Need specialized diets

Signs of autism in adults

Autism spectrum disorder is a lifelong condition. Although treatment can improve some outward symptoms, people with autism will always process sensations such as sound, sight, touch and smell in different ways.

Autism is a spectrum condition, which means that adults will have different experiences of day-to-day living. An adult with mild symptoms, who is towards the higher functioning range of the autism spectrum, may:[3][17][18]

  • Have difficulties with social interactions
  • Avoid making eye contact
  • Not understand nonverbal facial or body gestures, such as frowning or shrugging
  • Not understand changes in tone of voice, such as sarcasm
  • Be comforted by rules and routine
  • Get upset at changes to routines
  • Be under- or over-sensitive to loud noises, strong smells or tastes
  • Engage in repetitive behaviors, such as pacing or hand flapping
  • Have a narrow range of interests
  • Have a good memory and recall of facts

An adult who is towards the lower functioning range of the autism spectrum may:[6][18][19][20]

  • Never communicate verbally, or have only limited verbal skills
  • Need assistance with everyday living, such as bathing and dressing
  • Engage in repetitive behaviors, such as rocking
  • Insist on rules and routine
  • Become extremely distressed at changes to routine
  • Need specialized diets

Employment may present a challenge for adults with autism. People with autism are likely to need adjustments to be able to work productively, such as lights that do not flicker or a quiet space to work in.[21]

One common sign of autism spectrum disorder in adults is anxiety. Signs of anxiety can include:[22]

  • Irritability
  • Insomnia
  • Racing heart
  • Headaches
  • Dizziness
  • Constant thoughts about worst case scenarios
  • Depression

Adults with autism spectrum disorder may also experience meltdowns.

Signs of autism in girls

The ratio of boys to girls diagnosed with autism spectrum disorder is 4:1. However, there is some evidence that autism is going undiagnosed in girls, particularly those who are at the higher functioning end of the spectrum.

There is a belief among some researchers that diagnostic criteria are based on how boys and men display signs of autism, and that girls and women may have different symptoms. Past theories, including controversies such as the extreme male brain, may have led to under-referral and under-diagnosis of autism spectrum disorder in girls and women.[23][24]

Signs that a girl may have autism include:[25][26]

  • Difficulties with social interactions; however, differences from typical autism symptoms may include:
    • Better grasp of emotions and ability to make friends than boys
    • May mask lack of intuitive understanding of social situations by repeating role-plays seen in real life or film/television
    • May be able to make friends but find difficulty keeping them
  • Intense focus on particular topics; differences in gender may be expressed as a focus on trains or dinosaurs for boys, and celebrities or animals for girls,
  • Fewer repetitive behaviors and gestures than boys, or may have different gestures than boys
  • Reliance on rules and routine, however, that may be interpreted as good behavior in girls

There are also higher rates of anxiety, depression and eating disorders among girls with autism spectrum disorder than among boys.

Signs of Asperger syndrome

People with Asperger syndrome are generally considered to be on the higher functioning end of the autism spectrum. It is still a form of autism and is a lifelong condition.

Signs and symptoms that are typical of people with Asperger syndrome include:[27][28][29]

  • Very narrow and highly focused interests
  • Great importance on rules and routines
  • High standard of language skills, potentially very formal in expression
  • Monotonous or repetitive speech
  • Poor understanding of nonverbal communication, such as facial expressions and gestures
  • Difficulties with social interactions
  • Spending time alone to escape social interaction
  • Tendency to talk about self or own interests
  • Difficulty with making eye contact
  • Poor physical coordination

Repetitive behaviors

Many people with autism spectrum disorder engage in repetitive behaviors, known as stereotypy, self-stimulatory behavior or stimming. These behaviors provide the person with a form of sensory input that the person finds appealing or helpful. Examples of these kinds of behavior include:[15][30][31]

  • Flapping arms
  • Rocking from side to side
  • Jumping or hopping, including while seated
  • Flicking a rubber band or piece of string
  • Staring at lights
  • Twirling
  • Watching a moving object
  • Head banging
  • Making the same noise repeatedly
  • Scratching

Some people with autism develop extreme preferences, dislikes or practices around food, for example:[32][33]

  • Only eating food that falls into the same food groups, such as sweet, salty or bitter
  • Selecting or refusing foods based on texture, smell, color or temperature
  • Covering all food in sauce
  • Putting too much food in the mouth, where a person lacks sensory sensitivity
  • Biting inner lips and cheeks when faced with food they don’t like
  • Only eating food presented in the same manner each time

Challenging behaviors in autism

People with autism spectrum disorder may exhibit behaviors which put themselves at risk, cause difficulties for people around them or which are not socially acceptable.

Around 50 percent of people with autism engage in behavior that can cause themselves harm when they feel frustrated, overwhelmed or unwell. Such behaviors include:[34][35]

  • Banging head on walls or other objects
  • Hitting their head with their hands
  • Poking themselves in the eye
  • Pulling their hair
  • Scratching at their skin
  • Picking the skin
  • Biting themselves
  • Smearing feces

A person with autism who feels frustrated, overwhelmed or feeling unwell may also display physically aggressive behavior. This can include:[36][37]

  • Throwing objects
  • Hitting, slapping or biting other people
  • Pulling other people’s hair

Some people with autism eat objects that are not edible, or keep the objects in their mouth, a behavior known as pica. It is the most common eating disorder found in people with autism spectrum disorder. People may eat anything, including dirt or soap.[38][39]

Sensory overload

People with autism spectrum disorder often have difficulty processing sensory information around them. This can include:[3]

  • Sights
  • Sounds
  • Smells
  • Tastes
  • Sensations of touch

A person may be under- or over-sensitive to a sensation like noise, bright light or certain smells. This can cause them to lose focus, become upset or behave in unexpected ways in order to manage the sensations they are experiencing.

This sensory overload can also cause people with autism to not be able to look at others’ facial expressions when listening, or to be unable to focus on questions or complicated instructions at the same time as listening to another person talk.[16]

Signs of autism meltdown

For some people with autism, sensory overload can become overwhelming. In these situations a person may have a meltdown. A change in routine can also precipitate a meltdown.

A meltdown is not a temper tantrum and can be experienced by someone with autism of any age. A meltdown should be managed by calming the person and addressing the cause of the distress.

Signs that a meltdown may be developing, sometimes known as the rumbling stage, include:[40][41]

  • Nail biting
  • Pacing
  • Rocking
  • Being very still and tense
  • Asking lots of questions
  • Threatening others

If a meltdown is not successfully averted, the person may display full meltdown behaviors. These can include:[40][41]

  • Screaming
  • Crying
  • Punching
  • Kicking
  • Destroying objects
  • Hurting themselves
  • Biting

Gastrointestinal problems and autism

Up to 70 percent of people with autism spectrum disorder also have some form of gastrointestinal condition, which can include:[42][43][44]

  • Constipation
  • Diarrhea
  • Gastroesophageal reflux disease (GERD)
  • Chronic gastritis
  • Chronic duodenitis

Many people with autism spectrum disorder also have food intolerances and may find that a diet which excludes gluten or casein helps.[33]

Autistic savant

The perception of people with autism as having uncommon powers of memory and recall, as popularized in various media, is not representative of people with autism spectrum disorder as a whole.

Around 10 percent of people with autism spectrum disorder are thought to show some kind of savant skills, where a person with mental or physical disabilities displays certain abilities beyond those of the average person. These skills often take one of the following forms:[45]

  • Music, particularly playing the piano
  • Mathematics, particularly mental calculation
  • Art, often painting or drawing
  • Calendar calculating, the ability to identify the day of the week of any date over a wide time period
  • Spatial and mechanical skills, such as being able to measures distances without instruments or create complicated mechanical models
  • Memorization, usually utilized as part of another skill

It must be emphasized that 90 percent of people with autism spectrum disorder do not display savant skills.

Diagnosing autism

Most children with autism spectrum disorder display signs before they reach two years old. The American Academy of Pediatrics recommends that health professionals check for early signs of autism at children’s 18 month and 24 month old checks.

There are a variety of diagnostic tools used by pediatricians, psychologists, neurologists and other medical professionals.

When to seek medical advice

Early intervention is very important in children with autism spectrum disorder. Services such as speech therapy and behavioral and skills training are more effective if begun when a child is young.[46]

For this reason, it is helpful to receive a diagnosis as early as possible. However, many children remain undiagnosed until they are in school. Some people are not diagnosed until they are adults.

If you suspect someone has autism, including yourself, contact a medical professional as soon as possible.

Signs of autism FAQs

Q: How early can signs of autism be detected?
A: Doctors can confidently make a diagnosis of autism spectrum disorder by the time a child is two years old. However, it may be possible to see signs of autism in newborn babies and toddlers, such as delayed development of babbling and not responding to their name. See the sections on Signs of autism in babies and Signs of autism in toddlers.


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