What is autism?
Autism can be diagnosed in babies, children, tweens, teens, and adults.
Autism spectrum disorder (ASD) is a developmental disability that affects a person's behavior and impairs the ability to communicate and interact with others. Symptoms of autism spectrum disorder can range from mild to severe. The cause is unknown.
Autism spectrum disorder refers to several conditions that used to be diagnosed separately, including:
- Autistic disorder
- Pervasive developmental disorder not otherwise specified (PDD-NOS)
- Asperger syndrome
What are the early signs and symptoms of autism in infants and babies?
Some children may show symptoms of autism disorder in infancy, but many do not show any signs until 24 months of age (2 years) or later. Some signs and symptoms that an infant or baby may have an autism spectrum disorder include:
- Lack of eye contact
- Not responding to his or her name or to familiar voices
- No back-and-forth gestures, such as reaching, pointing, waving, or showing
- Does not make noises to get attention
- Does not initiate cuddling or respond to attempts to do so
- Absence of visually following objects or gestures
- Does not imitate facial expressions or movements
- Lack of interest in playing with other children
- Does not share interest or enjoyment in activities
- Seems not to notice if others experience pain or discomfort
In addition to the common symptoms that infants with autism may exhibit, some developmental red flags may also indicate autism spectrum disorder in infants such as a lack of smiles or other joyful expressions by 6 months of age, and no back-and-forth sharing of smiles, facial expressions, or sounds by 9 months of age.
What Causes Autism?
Autism is recognized as a set of a wide variety of signs and symptoms, and may have many causes. Autism is caused by, for example:
- Tuberous sclerosis
- Fragile X syndrome (inherited disorder)
- Cerebral digenesis (abnormal development of the brain)
- Rett syndrome (a mutation of a single gene)
- Some of the inborn errors of metabolism (biochemical defects)
- Strong association between:
- Autism and seizures
- Autism and Landau-Kleffner syndrome
- Acquired epileptic aphasia
What are the early signs and symptoms of autism in toddlers?
A toddler is a child age 12 to 36 months (1 to 3 years), and often this age is when parents start noticing the first signs and symptoms of autism spectrum disorder. Studies have shown up to half of parents of children with autism noticed signs before their child’s first birthday, and almost 80%-90% noted symptoms by 24 months.
In addition to the symptoms that infants with autism may exhibit, some developmental red flags that may indicate autism spectrum disorder in toddlers by 12 months old include:
- Not responding to their name
- Lack of babbling or "baby talk"
- Absence of back-and-forth gestures, such as reaching, pointing, waving, or showing
By 16 months, a red flag that a toddler may have an autism spectrum disorder is a lack of spoken words, and by 24 months, an absence of meaningful two-word phrases that don’t involve imitating or repeating may be noticed.
Autism is a developmental disability.
What are the early signs and symptoms of autism in older children and teens?
For older children and teenagers, signs and symptoms of autism spectrum disorders usually involve problems with speech and language, impaired social skills, non-verbal communication difficulties, and inflexible behavior. Symptoms may range from mild to severe. Some children may be severely disabled by symptoms, while others may be high-functioning.
Signs of speech and language difficulties include:
- Starts talking later than other children
- Problems communicating needs
- Lack of understanding of simple questions or directions
- Takes things literally (does not understand humor, sarcasm, or irony)
- Speaks in an unusual tone of voice, or with a strange cadence
- Repeats words and phrases over and over
- Repeats, rather than responds to, questions
- Does not use language correctly
- Refers to him- or herself in the third person
Signs of social communication problems include:
- Seems aloof and detached from others
- Difficulty connecting with others and making friends
- Seems disinterested or unaware of what is going on around them
- Does not like to be touched, cuddled, or held
- Difficulty playing “pretend” or using toys creatively
- Doesn’t share with others
- Doesn’t seem aware when others are speaking to them
- Difficulty understanding or expressing feelings
- Have trouble maintaining a conversation
- Talk a lot about a specific topic but have difficulty talking about a range of topics
- Find it hard to follow instructions with a lot of steps
Signs of nonverbal communication difficulties include:
- Difficulty picking up on subtle nonverbal cues from others (facial expressions, gestures, tone of voice)
- Avoidance of eye contact or unusual or inappropriate eye contact
- Facial expressions do not match what is being said
- Rarely makes gestures and may seem cold or robotic
- Has abnormal posture or eccentric ways of moving
- May be overly sensitive to sights, smells, textures, and sounds
Signs of inflexibility include:
- Insistence on a rigid routine
- Has problems adapting to changes in schedule or environment
- Forms unusual attachments to strange objects (such as keys or light switches)
- May obsessively line up or arrange objects in a particular order
- Becomes preoccupied with one narrow topic of interest, often that involves symbols or numbers such as train schedules or sports statistics
- Spends long periods watching moving objects or focusing on one part of an object
- Repetitive movements (called self-stimulatory behavior, or "stimming" - believed to soothe children with autism):
- Hand flapping
- Head banging
- Snapping fingers
- Flicking light switches on and off
What are other early signs and symptoms of autism in older children and teens?
Other signs and symptoms of autism in older children and teens include:
Are the early signs and symptoms of autism the same for girls and boys?
There are some differences between girls and boys with autism. Not every child shows (or does not show) certain behaviors, and certain aspects of behavior and interaction are more common in one gender versus another.
Girls with autism
- Tend to have at least one close friend - more sociable
- Are not demanding
- Auditory hallucinations (hears things others can't)
- Speaks her mind
- Can hide feelings
- Shows some affection
- Speaks on time and few problems with speech
- Speaks in high pitch
- Apologizes a lot (sometimes to excess)
Boys with autism
- Often have no friends - more reclusive
- Are very demanding
- Typically no auditory hallucinations
- Does not speak his mind
- Show emotions
- Speaks late and has speech impairment
- Monotone speech
- Rarely, if ever, apologizes - doesn't seem to care
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What are the early signs and symptoms of autism in adults?
In adults, signs and symptoms of autism are similar to those in older children and teens, including:
- Difficulty understanding what others think and feel, lack of empathy for others
- Anxiety in social situations
- Difficulty making friends or maintaining romantic relationships
- Preferring to be alone
- Coming across as rude or disinterested without meaning to be
- Problems with nonverbal communication (difficulty maintaining eye contact, interpreting facial expressions, or using gestures)
- Difficulty expressing feelings
- Trouble maintaining conversations
- Takings things literally (difficulty understanding humor, sarcasm, or irony)
- Sticking to a strict routine and getting anxious if anything changes
- Not understanding social "rules"
- Avoiding eye contact or showing inappropriate eye contact
- Invades personal space, or gets upset if others come too close to them
- Preoccupations or hyper-focus on certain subjects or activities
- Repetitive behaviors
- Anxiety and sleep problems
- Temper control issues
Autism may be different in women and men. It may be harder to tell if a woman is autistic. Women with autism may hide their feelings, may be quieter, and may appear to handle social situations more easily.
On the positive side, adults with autism may excel at a particular skill, have an abundance of knowledge in one specific area, or have an exceptional memory.
Is there a checklist of signs and symptoms for autism?
The Autism Research Institute has developed what is called Form E-2, used to diagnose children with Kanner's syndrome, which is also known as "classical autism." The E-2 checklist is also used to assist in the diagnosis of autism spectrum disorder (ASD).
AutisMag, an online news magazine, has an online Autism Symptoms Checklist Quiz that can be helpful in determining whether developmental delays may be signs of autism spectrum disorders.
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Medically Reviewed on 12/3/2019
Alexa, Mary. Autism in Girls. Autism.org. Updated: Dec 02, 2014.
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Signs and Symptoms of Autism Spectrum Disorders CDC. Updated: Aug 27, 2019.
Signs of autism in adults. NHS UK. Updated: Apr 18, 2019.
Signs of autism spectrum disorder in older children and teenagers. Raising Children Network (Australia). Updated: Jun 21, 2018. 28 November 2019.
Smith, MA, et al. Does My Child Have Autism? Helpguide.org. Updaed: Nov 2019.
Augustyn, M, MD, et al. Patient education: Autism spectrum disorder (The Basics). Updated: May 28, 2019.