Are autism rates rising?

Changes in diagnostic criteria

What it means to be autistic has changed over the past 80 years. In the 1940’s, the disorder was only attributed to children who displayed symptoms that today would be described as ‘severe’.

It wasn’t until the 1990s that autism was thought of on a scale, with people considered anything from mildly autistic to severely autistic. This was ratified in 1994 when the APA released the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), declaring autism a spectrum disorder.

Prior to 2013, Asperger’s syndrome, pervasive developmental disorder, Rett syndrome, childhood disintegrative disorder, and PDD-NOS were all regarded as distinct autism spectrum diagnoses. ^[2] Following the APA’s publication of the DSM-V in 2013, anyone with symptoms of autism receives the same blanket diagnosis of autism spectrum disorder (ASD). ^[2]

It follows that more people now meet the conditions required for an autism diagnosis, meaning a rise in autism rates.

Environmental/social factors

The exact cause of autism remains unknown, but a wide range of studies have found that environmental and genetic factors are involved in autism contraction. ^[3]

These are largely associated with events during pregnancy and the birth of the child. Examples include: ^[3]

• Advanced parental age – maternal or paternal age equal to or above 34 years is associated with an increased risk of autism in their offspring.
• Maternal physical health – bleeding, infection and metabolic syndrome during pregnancy are examples of mother’s diseases that are linked to a higher risk of autism. Viral infections occurring in the first trimester, such as measles, mumps, rubella, chicken pox, influenza, pneumonia, elevate the risk of autism in the embryo.

Pregnancy obesity and extreme weight gain during pregnancy are linked with greater incidence of autism.

• Maternal mental health – there is a positive correlation between parents with a history of psychiatric disorders and their children developing autism. A schizophrenic parent has 3 times the chance of having an autistic child, whilst mothers who experience depression, anxiety or other mental health disorders are more susceptible to birthing children with autism.
• Prenatal exposure to air pollution or pesticides – can adversely affect fetal health and damage neurodevelopmental process.
• Maternal prenatal medication – accounts for a 46% increased risk of fetus autism. This is due to cross-contamination between the medication and the placenta disturbing fetal development.
• Familial socioeconomic status – families grappling with financial problems experience poorer quality of life, characterized by elevated stress and anxiety levels and poor accessibility to good healthcare. This can cause psychological tension to parents, especially pregnant mothers, leading to an increased risk for child autism.
• Postnatal risk factors – these include low birth weight, premature birth, jaundice, and postnatal infections (such as meningitis, mumps, or ear infections).

Will autism rates continue to rise?

Whether autism rates will continue to rise cannot be established definitively. Further changes to diagnostic criteria could increase or decrease autism rates, depending on what symptoms qualify for diagnosis.

Increased awareness about the condition, greater education, and evolving medical treatments could lead to a decline in autism diagnoses.

Alternatively, this could spur more parents to bring in children for autism evaluations, with improved screening practices across the whole of society uncovering a greater number of diagnoses than previous years.