Autism risk factors: what is linked to a higher chance of autism

What autism is

ASD is a neurological and developmental disorder that affects how people interact with others, communicate, learn and behave. It can be diagnosed at any age, but it is called a developmental disorder because symptoms generally appear in the first two years of life (NIMH). It is called a spectrum disorder because people with autism have a range of characteristics, needs, strengths and challenges (NIMH). ASD includes what used to be known as Asperger syndrome and pervasive developmental disorders (MedlinePlus).

People of all ages, races, ethnicities, sexes and economic backgrounds can be diagnosed with ASD (NIMH). There is no score or calculator on this page; the factors below are the ones NIMH names.

Factors linked to a higher chance of autism

Researchers do not know the primary causes of ASD. Studies suggest that a person's genes and aspects of their environment may affect development in ways that lead to ASD (NIMH). MedlinePlus also says the causes are not known and that research suggests both genes and environment play important roles (MedlinePlus). NIMH lists these factors as associated with an increased likelihood of ASD (NIMH):

• Having a sibling with ASD (NIMH).
• Having older parents (NIMH).
• Having certain genetic conditions, such as Down syndrome or Fragile X syndrome (NIMH).
• Having a very low birth weight (NIMH).

Not everyone who has these factors will develop ASD (NIMH).

Signs and symptoms

Not all people with ASD have all of these behaviors, but most have several (NIMH):

• Social communication and interaction: little or inconsistent eye contact, not responding or being slow to respond to their name, difficulty with the back and forth of conversation, talking at length about a favorite subject without noticing social cues, facial expressions or gestures that do not match what is being said, trouble understanding another person's point of view, and difficulty with imaginative play or making friends (NIMH).
• Restricted or repetitive behaviors: repeating words or phrases (echolalia), lasting intense interests in specific topics, overly focused interests such as moving objects or parts of objects, and becoming upset by slight changes in routine (NIMH).
• Sensory differences: being more or less sensitive than other people to light, sound, clothing or temperature (NIMH).

People with ASD may also have sleep problems and irritability. Many also have strengths, such as learning things in detail and remembering information for long periods, being strong visual and auditory learners, and excelling in math, science, music or art (NIMH).

How autism is diagnosed

Health care providers diagnose ASD by evaluating a person's behavior and development. ASD can usually be reliably diagnosed by age 2, and the earlier it is diagnosed, the sooner treatments and services can begin (NIMH).

• Young children: often a two-stage process. The American Academy of Pediatrics recommends developmental screening at the 9-, 18- and 24- or 30-month well-child visits, with specific autism screening at 18 and 24 months. A child may get more screening if they have an increased likelihood of ASD. A team of specialists then does a fuller evaluation, which may include medical and neurological exams, speech and language assessment, observation, family history, and sometimes blood tests and a hearing test (NIMH).
• Older children and teens: caregivers and teachers are often the first to notice. The school's special education team may do an initial evaluation and recommend further evaluation by a health care provider (NIMH).
• Adults: diagnosis is often harder, because some symptoms overlap with mental disorders such as an anxiety disorder or attention-deficit/hyperactivity disorder (ADHD). Adults who wonder whether they are on the spectrum can ask a health care provider for a referral to a neuropsychologist, psychologist or psychiatrist with ASD experience (NIMH). See ADHD risk factors and anxiety risk factors.

Treatment, services and getting help

Interventions, services and supports work best when they begin as soon as possible after diagnosis. There is no single best approach; people may be referred for behavioral, psychological, educational, occupational, physical or speech-language therapy. A health care provider may prescribe medicine for specific symptoms such as anxiety, depression, hyperactivity, irritability or self-injurious behavior (NIMH). A health care provider, local health department, school, community center or autism advocacy group can point to local programs (NIMH).

The 988 Lifeline is free and confidential and available 24/7 (988 Lifeline).

Common questions

Is autism genetic?

Genes play a role, along with aspects of the environment (MedlinePlus). Having a sibling with ASD and having certain genetic conditions such as Down syndrome or Fragile X syndrome are linked to a higher likelihood (NIMH).

When should a child be screened for autism?

The American Academy of Pediatrics recommends specific autism screening at the 18- and 24-month well-child visits, and NIMH says caregivers should talk to their child's health care provider about screening or evaluation (NIMH).

Can adults be diagnosed with autism?

Yes. Autism can be diagnosed at any age, although diagnosis in adults is often more difficult than in children (NIMH).