What Is The Cause Of Autism? An In-Depth Look At Risk Factors

By Corrina Horne

Updated October 09, 2019

Reviewer Lauren Guilbeault

Most doctor visits require you to sit and fill out an information sheet detailing not only your information and why you are there but also information about your immediate and extended family. Typically, these questionnaires focus on chronic diseases within your family, and any unusual presentation of standard bodily functions. Doctors and therapist take these assessments to determine whether or not they should be on the offense in searching for any patterns of illness in a patient's family. Autism is one such pattern.

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Despite the increased incidence of autism in recent years, researchers still know very little about the actual cause of autism. The symptoms, outcomes, and effects of autism are largely known now, including how autism is best treated and addressed. Still, autism's origin is elusive.

At its inception, autism was thought to be a result of children not being loved and cared for properly. From there, it was considered a form of schizophrenia and was regarded as a type of psychosis. Still, further down the line, autism was recognized as its own unique diagnosis, but despite at least 50 years of research, autism continues to stump research teams and doctors alike as to what exactly it is that triggers autism in children.

What Is Autism?

Autism is actually called Autism Spectrum Disorder (ASD) and is a developmental disorder, which focuses on a child's ability to function socially. Whereas typical children pick up on social cues, learn the language, and interact with others without a lot of coaching or difficulty, children with autism do not read social signals the way a typical peer might. They often present with language delays, difficulty communicating, disinterest in playing with peers, and limited imaginative play.

Autism is most often recognized in the early toddler years but can go undetected (or undiagnosed) into adulthood. Children with autism who do not receive a diagnosis are very often misdiagnosed as having ADHD, OCD, and a host of other disorders, when the root cause of the behaviors associated with those disorders is Autism Spectrum Disorder.

Maternal Risk Factors

The most striking maternal risk factors rise in pregnancy. If a mother gives birth to a preterm child, that child is at higher risk for an autism diagnosis. Low birth weight is also a risk factor, which is almost always at play in preterm birth. Pregnancy complications, including pre-eclampsia and restricted growth, might also have a link to a child's risk of having autism.

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Aside from pregnancy, though, mothers may carry genetic risk factors that could increase the likelihood of their children receiving an autism diagnosis. Depression in mothers has been consistently linked to the development of autism in a child, as has the presence of any learning delays in a mother's history. Having children over the age of 40 has also been linked to an increased incidence of disabilities, including autism.

Paternal Risk Factors

The most pronounced paternal risk factor is a father's age at a child's conception. The precise "why" of this risk factor is not known, but studies continually find that as men age, their children develop higher risks of developing a number of disorders, including autism and ADHD. This process seems to start at age 34, and the risk increases as fathers get older.

Paternal diagnoses of schizophrenia and affective disorders were also important risk factors, and fathers with a previously-diagnosed condition of schizophrenia, ASD, or ADHD were significantly more likely to have a child with ASD than fathers who did not have any prior diagnoses or childhood disorders or delays.

Familial Risk Factors

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A child's siblings and cousins can also help doctors screen for autism, as a child with a sibling with autism is 9 times more likely to have the disorder, and a child with a cousin with autism is twice as likely to receive an autism diagnosis. Although the exact genetic mechanisms behind this connection remain unclear, enough data has been collected to support the notion that autism runs in families-both in immediate and extended families.

What Causes Autism? Nature Versus Nurture

Nature and nurture are both involved in the development of autism, as research consistently suggests that both genetic and environmental triggers are responsible for Autism Spectrum Disorder. Family history often reveals the presence of mental, mood, or learning disorders that may play a role in a child's developmental challenges. Birth weight, carrying to term, and pregnancy complications are also often acknowledged as part of the puzzle in figuring out why some children have autism and others don't.

Children with autism often have sensitive systems, which can be overtaxed by environmental toxins. The presence of weed killer, for instance, might not demonstrate lasting effects on a typical child, but a child with autism's body might have a strong reaction, leading to increased stimulatory behavior, aggression, or reticence. Children with autism usually have sensory issues, which can lead to symptoms of regression, confusion, and disconnect. Because a child's environment cannot be strictly controlled and monitored at all times, autism symptoms often seem to ebb and flow, achieving great highs and great lows.

Are Vaccines Involved?

Some concerns arose regarding vaccines and autism, with one study suggesting the MMR vaccine causes autism. This study was largely debunked, however, as one of the authors of the study acknowledged the study was flawed in its outlook and left out many important research factors. Still, the notion that vaccines cause autism has taken root in the minds of many men and women and is a concept that has had a hard time finding root in reality.

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The presence of heavy metals within vaccines (thimerosal, in particular) has been causing for concern for some parents, who have children with heavy metal toxicity in their body-a condition that has been linked to autism. As of yet, the source of this toxicity is often unknown, and no causative link has been made between vaccines and heavy metal toxicity. Indeed, high levels of lead in children's bodies are more often a result of contaminated water and lead-based paint, rather than medicinal systems pushed by pediatricians.

Possible Environmental Factors

Environmental toxins can play a role in whether or not a child has autism. As discussed briefly above, children with ASD have extremely sensitive bodies and brains and can react powerfully to triggers that other children might not react to at all. Although the exact reason for this remains unknown, many children with autism have a weakened immune system from birth and are more susceptible to gut imbalances and illnesses, as well as suffering from chronic ear infections and disturbed vestibular input. A child who is often sick and whose body is regularly fighting infection might not have the mental or physical capacity to develop at the pace expected of their healthy peers.

Heavy metal toxicity can also play a role in autism development. Old pipes and old paint are the most likely sources of toxic lead exposure, but many children with autism have other heavy metals in their systems-another phenomenon that is not yet understood. Whether it is copper or aluminum, many children with autism have an excessive amount of toxic load built up in their bodies. This could be due to a weakened immune and filtering system, as some children with autism have liver and kidney issues.

Food allergies and sensitivities have also been linked to increased autism symptoms; children with autism seem to have more sensitive stomachs and, correspondingly, sensitivities to more foods than their typical peers. Continually eating allergenic food can cause chronic inflammation in a child's body, which can further impede development. For this reason, some families choose to engage restrictive diets, to try to heal children's intestinal permeability and improve autism outcomes.

What Causes Autistic Spectrum Disorder?

The cause of Autism Spectrum Disorder is still largely a mystery. Although scientists have identified certain risk factors in a child's environment and family history, the exact reason for these risk factors remains unknown and fall firmly into a category of "did the chicken or the egg come first?" Because children with autism can have such sensitive and easily overwhelmed bodily systems, autism symptoms might be further aggravated by the pace of life, the presence of constant stimulation via television and phones, and the levels of pollution common to most cities. Children with autism carry a heavy burden of toxic overload, and can easily grow exhausted trying to navigate the world around them.

Research continues to dive into the mechanisms and root causes behind autism. As autism rates grow, and the number of interventions required places increasingly large demands on state and federal government systems, the urgency to better understand and heal autism is increasing. Because interventions to limit the symptoms of autism can be vast-and expensive-many families are brought to the brink of despair trying to care for their children. For this reason alone, more intensive research is still required to get to the bottom of what exactly autism is, and why it affects so many children in the present day.


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