Note: The following information does not replace consultation with a specialist for diagnosis.

Autism, or Autism Spectrum Disorder (ASD) as it is technically known, is a health condition characterized by impairments in three significant areas of human development: socio-emotional skills, shared attention, and language. Today, science recognizes not just one type of autism, but many different types, each manifesting uniquely in every individual.

The term “spectrum” is used to define the broad range of autism because there are various levels of impairment. This spectrum ranges from individuals with other associated diseases (known as comorbidities), like intellectual disability, to those who lead ordinary, independent lives, some of whom may not even realize they are autistic due to a lack of diagnosis. (See also our article “What are the signs and symptoms of autism?”)

Genetic Causes

Autism is a multifactorial disorder, and its causal mechanisms are not fully understood. A study published in JAMA Psychiatry on July 17, 2019, suggests that 97% to 99% of autism cases have a genetic cause, with 81% being hereditary. The study, involving 2 million individuals from five different countries, also indicates that 18% to 20% of cases have a somatic genetic cause (non-heritable). The remaining 1% to 3% are likely due to environmental factors, such as intrauterine exposure to drugs, infections, or trauma during gestation (read our article “Research Confirms Autism is Almost Entirely Genetic; 81% is Hereditary”). In November 2022, a scientific paper from the Hospital for Sick Children (Canada), published in the journal Cell, identified 134 main genes related to autism based on genetic sequencing of 20,000 people, including those with autism and their relatives. Specific mutations in these genes are strongly associated with the risk of ASD.

After hundreds of studies, including the American MSSNG project published in 2017 in Nature Neuroscience – considered the largest genetic study program on autism worldwide – it is known that genetic tests can detect the cause in 10% to 40% of ASD cases in the USA and Canada. This detection rate is higher when modern genetic analysis technologies are used, especially in cases where autism is associated with other health issues and clinical signs. Over a thousand genes have been mapped and implicated as risk factors for the disorder, with 134 being the primary autism-related genes.

Signs of Autism in Childhood

Signs of autism can appear as early as eighteen months of age, and even earlier in more severe cases. Early treatment initiation is crucial, even if it’s just a clinical suspicion, as earlier interventions can significantly improve the individual’s quality of life. According to the American Psychiatric Association, the psychological treatment with proven efficacy is behavioral intervention therapy, applied by psychologists. The most common of these is Applied Behavior Analysis (ABA). Since autism treatment is interdisciplinary, patients may also benefit from speech therapy, occupational therapy, and other professional interventions.

Below are some signs of autism, but it’s important to note that the presence of just three of these in an eighteen-month-old child warrants consulting a pediatric neurologist or a child and adolescent psychiatrist. Tests like the M-CHAT (including its Portuguese version) are available online for professional use. Learn more in our article about the signs and symptoms of autism.

• Difficulty maintaining eye contact for more than 2 seconds.
• Not responding when called by name.
• Isolating or showing no interest in other children.
• Lining up objects.
• Being excessively attached to routines to the point of crisis.
• Not using toys conventionally.
• Making repetitive movements without apparent function.
• Not speaking or using gestures to indicate wants.
• Repeating phrases or words inappropriately without functional use (echolalia).
• Not sharing interests or attention, such as not looking when something is pointed out.
• Spinning objects without a clear purpose.
• Restricted interests or hyperfocus.
• Lack of imitation.
• Not engaging in pretend play.

Information and Statistics on Autism

Here are some key data and statistics about ASD in Brazil and worldwide, with links to information sources and scientific studies:

• The term “autism spectrum disorder” has been used since 2013, with the release of the latest version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) by the American Psychiatric Association. This version consolidated four diagnoses under the ASD code 299.00: Autism, childhood disintegrative disorder, pervasive developmental disorder not otherwise specified, and Asperger’s syndrome. In the current International Classification of Diseases, the ICD-11, autism is listed under code 6A02 (formerly F84 in ICD-10), updated in June 2018.
• Approximately one-third of individuals with autism remain non-verbal.
• An estimated one-third of individuals with autism have some level of intellectual disability.
• Certain clinical conditions are more commonly associated with autism, including gastrointestinal disorders, seizures, sleep disturbances, Attention Deficit Hyperactivity Disorder (ADHD), anxiety, and phobias.
• In 2007, the United Nations declared April 2nd as World Autism Awareness Day, when landmarks around the world light up in blue to raise awareness, such as the Christ the Redeemer in Brazil, the Empire State Building in the USA, the CN Tower in Canada, the Eiffel Tower in France, and the Egyptian pyramids.
• In Brazil, the “Berenice Piana Law” guarantees the rights of individuals with autism, equating them to those with disabilities.
• The Centers for Disease Control and Prevention (CDC) in the United States estimates that 1 in 36 children in the country have autism, based on 2020 data. The prevalence in boys is 3.8 times higher than in girls.
• Studies in Asia, Europe, and North America report autism prevalence rates between 1% and 2%.
• The World Health Organization (WHO) estimates that approximately 1% of the global population falls within the autism spectrum, with the majority yet undiagnosed.
• Brazil has only one prevalence study of ASD to date, a pilot study conducted in Atibaia (SP) in 2011, which found a prevalence of 1 in 367 inhabitants (or 27.2 per 10,000).
• An online map on the Spectrum News site provides all the published scientific studies on autism prevalence worldwide.
• Regarding adults with autism, the CDC published a study in 2022 estimating that 2.2% of the U.S. population over 18 years of age are on the autism spectrum, based on 2017 data. There is no such data for adults with autism in Brazil.
• It is estimated that each year, about 50,000 young people with ASD turn 18 in the USA. There are no specific figures for Brazil.
• A 2012 study by Autism Speaks estimated the annual cost of autism in the USA at $126 billion and in the UK at £34 billion (approximately $54 billion).
• The average age of diagnosis in the USA is 4 years, according to a 2018 study. In Brazil, a pilot study only in São Paulo (SP) in 2018 found the average age of autism diagnosis to be 4 years and 11.5 months, but with a wide variation.
• Research indicates that about 16% of people with Down syndrome also have autism.
• There are syndromes and other neurological disorders of genetic origin linked to autism, such as Rett Syndrome, CDKL5, Timothy Syndrome, Fragile X Syndrome, Angelman Syndrome, Prader-Willi Syndrome, Phelan-McDermid Syndrome, and others.
• According to a global study in 2019, involving more than 2 million people from five different countries, 97% to 99% of autism cases may have a genetic cause, with 81% being hereditary; and 1% to 3% may have environmental causes, which are still controversial, such as advanced paternal age or use of valproic acid during pregnancy. Currently, more than a thousand genes have been mapped and implicated as risk factors for the disorder, with 134 being the primary genes.

[Updated on August 22, 2023]

For more news and information about autism and related syndromes, visit the Tismoo Biotech Portal (tismoo.us/portal/), which also covers other genetic neurological disorders linked to ASD (articles in Portugues).