Autism and Socioeconomic Status—An Immune Link?

Durkin et al.¹ demonstrated a positive socioeconomic status (SES) gradient with the prevalence of autism spectrum disorder (ASD) in the United States, as well as a rise in ASD in the same population from 2002 to 2010. They inferred, as have previous studies of autism and SES,² that this positive correlation with SES may be attributable to biased case ascertainment in the context of access to health and educational services. In addition, they found that this relationship was present among children with ASD without co-occurring intellectual disability. A positive correlation between autism and SES has been found in some other countries but not in others.

Idiopathic ASD, unlike ASD attributed to specific genetic mutations, constitutes the large majority (≥ 80%) of ASD cases. These cases tend to skew toward less intellectual disability, are increasing in prevalence, have a greater male–female sex bias, and may have an environmental rather than a genetic basis.

An increasing number of studies have reported immune dysregulation or infection involved in the etiology of autism,^3,4 including aberrant prenatal and postnatal microbial exposure, gut dysbiosis, maternal immune activation,⁵ cytokine and chemokine abnormalities, and an increase in autoimmune disorders, including type 1 diabetes, in families with children with autism.⁶ In addition, inflammatory animal models of autism replicate autistic behaviors and features.⁷

It is interesting that type 1 diabetes and other autoimmune disorders have also been shown to have a positive correlation with SES in multiple countries,² as well as a general increase in prevalence over a period of time similar to that described by Durkin et al.¹ The correlation with SES in autoimmune or inflammatory disorders has generally been attributed to the lack of or aberrant prenatal or postnatal microbial exposure in the context of early immune system development, leading to immune dysregulation. Moreover, the features of immune dysregulation described for autism have long been identified in autoimmune disorders, including an increase in other autoimmune disorders in families with a proband with any given autoimmune disorder.

As Durkin et al. inferred,¹ access to health care resources and educational services likely has an influence on the prevalence of autism diagnosis. However, especially in idiopathic autism, some consideration should be given to the possibility that the positive correlation of autism with SES might have a biological basis and may be a link to autoimmune or inflammatory disorders with a similar positive correlation with SES.