Autism Spectrum Disorder (Matoba, 2020) – Is Autism Genetic?

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Is autism genetic? Sample report from Nebula Genomics.
Variants in an autism spectrum sample report

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Additional information

Introduction (Part 1 of Is autism genetic?)

Autism is a pervasive developmental disorder characterized by challenges in social communication and interaction, along with restricted and repetitive patterns of behavior, interests or activities. Prior to 2013, autistic disorders were divided into multiple subcategories such as Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS). In 2013, the name autism spectrum disorder (ASD) was adopted to describe the wide range of diverse autism phenotypes. It usually occurs before the age of three and qualitative symptoms can be associated with ASD, including:

  • Problems with social interaction and exchange (such as understanding and building relationships)
  • Conspicuousness in verbal and non-verbal communication (such as eye contact and body language)
  • Limited interests with repetitive, stereotypical behavior

People with ASD also have an increased risk of psychiatric problems such as anxiety, depression, obsessive-compulsive disorder, and eating disorders.

Is Autism Genetic?

The genetic causes of the entire range of the spectrum are extremely diverse and highly complex and thus no specific genetic cause is acknowledged. The risk of autism may be associated with environmental factors as well. There does appear to be a large genetic component to autism as almost 20% of younger siblings of a child with ASD will receive a diagnosis themselves, higher than the CDC-reported 1% to 2% risk among the general population.

Changes in over 1,000 genes have been reported to be associated with ASD, but a large number of these associations have not been confirmed. Many of the genes associated with ASD are involved in the development of the brain. Some twin studies show that it is a highly heritable condition and, as of 2009, known genetic syndromes, mutations, and metabolic diseases account for up to 20% of autism cases. It is generally assumed that the immense combination possibilities of many genotypes cause the great diversity and breadth of the spectrum.

Autism puzzle
Many genes associated with autism are involved in brain development.

Autism may be caused by a spontaneous mutation on a single gene, mutations affecting multiple genes, multigene interactions, and/or epigenetics. It may also be associated with other disorders such as Fragile X Syndrome. According to the CDC, a national parent survey found that 46% of males and 16% of females with Fragile X Syndrome have been diagnosed or treated for ASD. Others have suggested that environmental factors combined with a genetic predisposition increases the risk factors for autism. 

Submicroscopic changes in chromosomes also play a key role in autism, namely copy number variations. Chromosomal abnormalities most often happen in the form of gene duplication or gene deletion that occur when the mother’s eggs or the father’s sperm cells (meiosis) are formed. 

Diagram of gene deletion and duplication.
Gene deletion (left) and duplication (right). Richard Wheeler (Zephyris) Attribution-Share Alike 3.0 Unported.

However, if a child receives such a deviation from one of the parents, it can be passed on, with a 50% probability. Thus, it is possible that an abnormality that contributes to the disorder occurs only once in a child and is not passed on, or it may affect several family members in different generations. The impact (penetrance and expressiveness) of such a genetic abnormality can also vary greatly from person to person.

Identical twins usually both have an autism spectrum disorder. Exceptions to this rule are attributed to environmental factors and epigenetic influences. Modern analytical methods (DNA chip technology) allow the detection of genetic abnormalities that lead to the expression of the spectrum disorder. The results can then form the basis of genetic consultations.

Epidemiology (Part 3 of Is autism genetic?)

The number of autism cases has risen sharply in recent decades. The Centers for Disease Control and Prevention (CDC) in the United States, a part of the U.S. Department of Health & Human Services, reported a 57% increase in children born with autism between 2002 and 2006. In 2006, 1 in 110 children aged 8 years were affected. Although better and earlier diagnosis plays a role, according to the CDC it cannot be ruled out that part of the increase is due to an actual increase in cases. 

In 2020, the CDC reported that about 1 in 54 children has been identified with ASD according to estimates from CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network made in 2016. ASD is reported in all racial, ethnic, and socioeconomic groups. It is more than 4 times more common in boys than in girls. 

Characteristics of Autism (Part 4 of Is autism genetic?)

Autism may present itself in diverse ways. Symptoms of autism can be mild to severe, with different levels of ability and disability.

Childhood autism

This is the most common form of autism. According the American Psychiatric Association, The most important areas affected in children and adolescents with autism are:

  1. Social interaction: A qualitative impairment of social interaction is sometimes already evident between 0 – 2 years due to a lack of contact with parents, especially the mother. Many children with autism do not stretch out their arms to the mother to be lifted. They do not smile back when they are smiled at and do not make appropriate eye contact with the parents. Children also show a strong object-relatedness, often limited to a specific type of object or restricted interests.
  2. Communication: About one in two children with early childhood autism does not develop spoken language. In the others, speech development is delayed. Most pronounced is the impairment of pragmatics: In communication with other people, autistic people have difficulties in understanding what is said beyond the exact meaning of the word, in reading between the lines. Their voice often sounds monotonous (missing prosody). Autistic children have an individually varying need for physical contact. Some take up direct and sometimes socially inappropriate contact with strangers, while for others, the sense of touch can be unpleasant for them due to the hypersensitivity of this sense.
  3. Repetitive and stereotypical behavior patterns: Changes in their environment worry and unsettle some autistic people. Sometimes they become upset when objects are no longer in their usual place or in a certain arrangement, or are distressed by an unannounced visit or spontaneous change of location. Actions are usually ritualized, and deviations from these rituals lead to chaos in the mind, because autistic people usually have no alternative strategies for unexpected changes in situations or processes.
Signs of childhood autism
Signs of childhood autism. MissLunaRose12. Attribution-Share Alike 4.0 International

High functioning autism 

If all symptoms of early childhood autism occur together with normal intelligence (an IQ of more than 70), children are often diagnosed with high-functioning autism (HFA). Diagnostically important here is especially the delayed child development of speech. Compared to the Asperger syndrome, the motor skills are usually significantly better.

Often, due to the delay in speech development, low-functioning early childhood autism (LFA) is diagnosed first. However, normal speech development can then take place later. Many HFA patients are therefore indistinguishable from Asperger’s patients as adults, but in most cases the autistic symptoms remain much more pronounced than in Asperger syndrome. 

Asperger syndrome

Asperger syndrome (AS) is considered a mild form of autism and manifests itself from about the age of four. Although many behaviors make heavy demands on the social network of those affected, especially those of close acquaintances and family, there are not only negative aspects of Asperger’s. There are numerous reports about the simultaneous appearance of above-average intelligence.

Symptoms and Diagnosing ASD (Part 5 of Is autism genetic?)

Children are normally diagnosed between 18 months and 2 years of age. Diagnosis is based on behavior, not cause or mechanism. Under the The Diagnostic and Statistical Manual of Mental Disorders (DSM–5), a diagnosis of ASD is characterized by:

  1. Persistent deficits in social communication and interaction across multiple contexts
  2. Restricted, repetitive patterns of behavior, interests, or activities
  3. These deficits are present in early childhood, typically before age three
  4. These symptoms cause clinically significant impairment in social, occupational, or other important areas of current functioning
  5. The disturbance must not be better accounted for by Rett syndrome, intellectual disability or global developmental delay

Sample symptoms include lack of social or emotional reciprocity, stereotyped and repetitive use of language or idiosyncratic language, and persistent preoccupation with unusual objects.

Treatment (Part 6 of Is autism genetic?)

Treatment is based on the individual development of each patient. The National Institutes of Health and the National Institute of Mental Health are actively conducting clinical studies that prevent, detect, or treat ASD.

Behavioral Therapy

Behavioral therapy is a common strategy to treat autism. The aim is to reduce disturbing and inappropriate behavior such as excessive stereotypes or (auto)aggressive behavior on the one hand and to build up social and communicative skills on the other. It focuses on social skill development, especially at young ages, and reduction of characteristic repetitive behaviors. In principle, this is done in such a way that desired behavior is consistently and recognizably rewarded (positive reinforcement). Occupational and speech therapy are also helpful with some children.

Drug treatment

There is no drug to treat this disorder. However, drug treatment of accompanying conditions and symptoms, such as anxiety, depression, aggressiveness or compulsions with antidepressants (such as SSRIs), antipsychotic drugs, stimulants, and mood stabilizers.

Prognosis (Part 7 of Is autism genetic?)

Autism can significantly affect personality development, career opportunities, and social skills. The long term course of a disorder depends on the individual characteristics of each patient. There is currently no cure for autism. 

Many of the difficulties reported by autistic people can be avoided or reduced by adjusting their environment. For example, some people report a sensation of pain for certain sound frequencies. Such people are significantly better off in a low irritant environment. Finding or creating an autistic appropriate environment is therefore an essential goal.

Communication training for autistic people and their friends and relatives through specially trained teachers and educators can be helpful. An increasing number of schools, colleges, and employers specifically for autistic people demonstrate the success of having autistic people live in autism-friendly environments.

Autism awareness heart
Many people with autism ask for tolerance and acceptance.

The manifestations of the disorder cover a broad spectrum. Many people with autism do not want a “cure” because they see it as part of themselves and not as a disease that needs to be cured by health care. Many adults with mild autism have learned to cope with their environment. Instead of pathologizing, they often wish for tolerance and acceptance.

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