Why Has The Incidence Of ASD Increased?

Is there an epidemic?

Great question. Many have become concerned as of late about an “autism epidemic”, but is this a real dilemma? If so, what is going on? Is it the red dye? The cell phones? Tylenol? Too much fluoride? It must be the vaccines right? The answer is none of the above. Despite the reasonable concerns about the above topics, none have been found to CAUSE autism.

There has certainly been debate and curiosity regarding the potential causes of autism and whether they are important or irrelevant, require a cure, or just require acceptance and embracement. Some autism-based organizations have focused their funding on “find a cure” rather than improving access to needed supports. From a treatment perspective, the etiology of autism if largely irrelevant; however, for some parents it can feel very important from an emotional standpoint.

Let’s start with what we do know. We know that, and yes even RFK Jr. would agree, autism has a complex multifactorial etiology (meaning no one gene or factor is responsible). In fact, in 2020, a group of molecular biologists identified more than 1000 candidate genes and hundreds of de novo mutations (new mutation, not inherited) associated with autism. For example, Rett syndrome, which is now part of the autism spectrum, is a lifelong neurological disorder in females, caused by a de novo mutation in MECP2, resulting in neurological regression in toddlerhood, in addition to microcephaly (reduced head size), epilepsy, and motor impairments/stereotypies, is still largely based on behavioral presentation as gene was only recently identified, varies in severity and time of regression based upon nature of mutation.

We also know that there are possible environmental triggers including chemicals in our environment that may play a role in how autism presents or what genes are activated in a particular manner. Additionally, research has shown that advanced maternal (over 35) and paternal (over 40) age associated with increased for autism, which may be exacerbated in families with higher familial risk and when both parents are older, with up to 60% increased risk when both parents are above age cutoffs, as well as increased incidence amongst siblings, possibly from DNA damage of sperm/eggs due to aging. Moreover, there was a recent study of out Princeton that identified four phenotypic presentations (behavioral patterns/presentations) of genetic profiles for children who have been diagnosed with autism. This study further confirms the strong genetic role in autism and the different ways and timelines in which autism symptoms can be expressed, especially with co-occurring genetic conditions like Fragile X, Angolan, William’s Syndrome etc. There may also be some environmental factors that cause these genes to express in particular way including infection or high blood pressure while pregnant, preterm birth or birth complications, pollutants, and pesticides.

Many of us have wondered why the autism rate has increased so significantly in recent years, with some estimates being as high as 1 in 30 children. How could this possibly be? Is there truly an epidemic? Let’s consider some things that may play a role: the increased popularity and awareness in combination with a reduction of stigma, change in DSM diagnostic labels removing separate categories (CDD, Retts, Aspergers and the largest former category of them all: PDDNOS), many genetic conditions often are labeled as autism because many of the delays and behavioral presentations overlap (e.g., Williams Syndrome, Down syndrome, Fragile X, etc.), in fact- in the description of many genetic disorders- it will state “autistic-like symptoms.”

As you may already know, the increase in diagnosis likely related to improvement in diagnostic criteria, increased awareness, desire for practitioners to obtain beneficial services for families. Additionally, there are many medical and psychiatric disorders that have overlapping symptomatology with the behavioral symptoms used to define autism. Some of the most common comorbid diagnoses: Epilepsy, Intellectual Disability, Anxiety Disorders, ADHD, Depression, and Tic Disorders/OCD.

Moreover, many insurance companies requiring a diagnosis at each visit, requiring clinicians to report a diagnosis with minimal information. Additionally, many clinicians and companies that work within insurance parameters end up diagnosing based on questionnaires, limited collateral information, and minimal testing with variable psychometrics (valid/reliable) and outdated assessments not intended for those with lower support needs (e.g., Autism Diagnostic Observation Schedule, Second Edition; ADOS-2). And notably, many families are getting married later than in past generations, prioritizing their careers, and taking things slower, resulting in a later age of childbirth and thus and increased risk of having an autistic child as opposed to when average birth age was younger. Finally, a large portion of the increase in diagnoses are actually adults, who are seeking an explanation as to their life-long struggles and were never properly assessed or diagnosed during their childhood.

So this may explain a significant portion of the cases that are now falling within the statistics resulting in an “increased prevalence of autism” as we understand it today; however, the true incidence of autism has actually been generally stable since the time autism was first identified in the 1940s.