Home » Autism Diagnosis » What is the Broad Autism Phenotype?

What is the Broad Autism Phenotype?

September 22, 2023

Discussions about the shared traits between children with autism spectrum disorders and their undiagnosed parents often lead to pondering the broader autism phenotype. Is it possible for relatives of autistic kids to have autism spectrum disorder…to a lesser degree?

What is the Broad Autism Phenotype

Autism spectrum disorder is a medical diagnosis but the broader autism phenotype is not. Rather, it refers to subclinical cognitive, personality, and behavioral traits in relatives of autisitc individuals; relatives who do not meet the diagnostic criteria for an autism spectrum disorder as presented in the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5; American Psychiatric Association, 2013). 

A person who is not on the spectrum may have characteristics mirroring traits of their autistic relatives like: being socially awkward, an insistence on sameness, and narrow, fixed interests. Parents, especially, may look at their kids autistic traits, and identify milder versions of these in themselves, leading to questions about being “mildly” autistic, having borderline autism, or perhaps the autism phenotype.

This matter may stir up some controversy. Many feel it’s flippant to even refer to autism with a term like “mild”. For autistic individuals, who’ve battled stigma, bullying, and a lack of support, remarks like: “Well, everyone is at least a little autistic,” may be infuriating. 

This article will not focus on issues like pathologizing normal behavior and self-diagnosing autism, rather the benefits of understanding and studying the broad autism phenotype will be explored. But first, let’s take a more in-depth look at the broad autism phenotype and research validating its existence in relatives of autistic children.

The broad autism phenotype theory

The broad autism phenotype, or the broader autism phenotype as it is also known, may apply to individuals with language, cognitive, and personality traits that are milder than what may be observed in those on the spectrum (Landry & Chouinard, 2016). Such traits are often apparent in non-autistic family members, which is where the broad autism phenotype theory stems from. 

One of the earlier reviews of relevant literature (Bailey et al, 1998) found relatives, of those on the spectrum, are sometimes affected by challenges appearing to be related to autistic behaviors.  In particular, social and communication difficulties that may manifest in struggling to make and/or maintain friendships, having atypical or little verbal expressions and interactions, and being aloof or awkward when faced with social interaction.

Researchers have zoned in on particular features of the broader autism phenotype; a study (Kadal et al., 2014) suggested social impairment as a characteristic feature of the broad autism phenotype. The study revealed parents of children on the autism spectrum struggled to recognize neutral expressions—like autistic children, their parents may have deficits in recognizing ambiguous expressions.

From literature it seems the broad autism phenotype will mean an individual may be:

  • Uneasy and awkward in social situations
  • They may have difficulty understanding others (and sometimes themselves)
  • They could display mild language impairments
  • They may be compulsive about routines and obsessive about interests
  • They may be anxious 
  • Their sensory experiences and preferences may be atypical

These symptoms are all characteristics of autism; non-autistic relatives, however, may experience these in a less severe manner disqualifying them from an autism diagnosis.

A study embracing a genetic focus (Piven, 2001) concluded that embracing information on the broad autism phenotype (BAP) in relatives may give scientists a crucial, complementary approach for detecting the genes causing autism spectrum disorders (ASD).

Evidence of the BAP

The BAP was assessed in parents from multiple incidence autism families, parents from single incidence autism families, parents of a child with a developmental delay with no ASD, and parents of neurotypical children (Bernier et al., 2012). Findings from the study suggested traits of BAP, particularly in communication and social spheres, are present to a greater degree in parents from multiple incidence autism families, in comparison to parents from single incidence autism families and control parents.

If literature and studies show evidence of a broad autism phenotype (BAP) in relatives of those with ASD, shouldn’t these relatives also be on the spectrum, or at least diagnosed with a subtype of autism? 

When looking at autism subtypes according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; American Psychiatric Association, 2000) it almost seems like the BAP should fit into one of these categories of autism—it is important to note that these subtypes are no longer used by clinicians since the DSM-5 absorbed the categories into a single entity, autism spectrum disorder.

Similar to aspergers or PDD-NOS?

Asperger’s syndrome, listed under Pervasive Developmental Disorders in the DSM-4, is characterized by social and communication deficits and restricted and/or repetitive behaviors. But, children who received this diagnosis often had the same, or higher, intellectual capabilities and verbal skills as typically developing children. 

Pervasive developmental disorder not otherwise specified (PDD-NOS) was another subtype of Pervasive Developmental Disorders in the DSM-4, which some felt was a catch-all category for children who were on the spectrum but who did not meet the criteria for any of the other categories. 

But asperger’s and PDD-NOS should not be confused with the BAP. These classifications of autism are no longer used officially but an individual with previously diagnosed asperger’s or PDD-NOS have an autism diagnosis, not only autistic traits. Or according to the DSM-5: “Individuals with a well-established DSM-IV diagnoses of autistic disorder, Asperger’s disorder, or pervasive developmental disorder not otherwise specified should be given the diagnosis of autism spectrum disorder.”

It seems easy to establish what the BAP is not, but parents may want more information to clarify whether their autistic characteristics and traits would qualify for an ASD diagnosis or the BAP. 

“Mild autism”

When children receive an autism diagnosis, many parents speak about suddenly understanding certain personality characteristics and behavior in their kids. Parents and siblings may recognize that they too display some of these behaviors to a milder degree—it’s not uncommon to hear parents referring to themselves as mildly autistic. Could a questionnaire prove such sentiments?

The Broad Autism Phenotype Questionnaire

The Broad Autism Phenotype Questionnaire is a self-report questionnaire for adults. It contains 36 statements and it zones in on areas like aloofness, rigidity, and pragmatic language. 

Administering the (BAPQ) to 86 parents of autistic individuals and 64 community control parents, it seems the tool succeeded in both sensitivity and specificity requirements in detecting BAP (Hurley et al., 2007). The study found parents of children with ASD had significantly higher scores in three areas:

  • Aloof personality
  • Rigid personality
  • Pragmatic language

The authors (Hurley et al., 2007) were convinced that the Broad Autism Phenotype Questionnaire provided an effective and valid measure to characterize the BAP.

The BAPQ is not the only way the BAP is measured. In fact, the BAP can be defined using varying domains, it can be measured with multiple, different instruments, and even the manner of reporting may differ according to the technique used (Rubenstein and Chawla, 2018). 

Special Offer

Don't miss out on the Autism Parenting Summit.
Click here to sign up now!

In their systematic review of studies that measured BAP in parents of autistic children, Rubenstein and Chawla (2018) found percentages of BAP ranging from 2.6% to 80%. They also found the BAP to be more prevalent in fathers than in mothers. The authors suggested a more consistent approach to BAP measurement will allow improved etiologic research. 

Another study (Tan et al., 2020) provided the first evidence for a BAP expressed in a physical characteristic—the study demonstrated that for both females and males, facial masculinity in non-autistic siblings is increased, when compared to same-sex comparison groups.

Perhaps the future will deliver standardized measures of the BAP utilizing physical, genetic, and behavioral clues. But why is it so important to understand and research an autism phenotype, rather than concentrating on actual autism? Many scientists believe it may contribute to our understanding of the etiology of ASD.

Benefits of understanding the BAP

Investigating BAP profiles in families could provide insight into how phenotype profiles are inherited within families and create greater comprehension of underlying genetic mechanisms in specific families (Gerdts & Bernier, 2011).

Beyond the beneficial broadening of our understanding of ASD, Gerdts and Bernier (2011) also mention that consideration of BAP characteristics in relatives has crucial clinical implications concerning intervention planning. Understanding dynamics in a family, seeking treatment for their child on the spectrum, will have a direct influence on therapy goals and desired outcomes.

Many studies dealing with the BAP mention common traits like social awkwardness, aloofness, rigidity, insistence on sameness and even anxiety. A parent with autistic traits may be deeply uncomfortable when seeking intervention for their autistic child: phone calls, meeting a bunch of (healthcare) strangers, and adjusting to new environments may be stressful for a parent who may already be anxious and worried about their child.

A healthcare provider who is knowledgeable and sensitive to not only the characteristics of the child on the spectrum, but also the possibility that the child’s parents may possess BAP traits, will be in a better position to provide appropriate care. Ignorance of the BAP, on the other hand, may translate to therapy providers judging parents negatively as their social behavior may not conform to neurotypical expectations.

Maybe it is autism

No article about the BAP would be complete without mentioning that some experts believe it’s more fable than fact. Or according to Chown (2019):

  • The concept of “autistic traits” is due to the “misuse of language”
  • This absence of autistic traits shows there is no BAP
  • The BAP is more likely evidence of the fact that there are more people with autism than assumed

Parents may be more concerned about receiving appropriate support than scientific debates concerning autism phenotypes. Because if parents possess some of the same characteristics of their kids on the spectrum, like social communication difficulties, they may be carrying a double burden… with limited means of sharing it.


American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596

American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text rev.). doi:10.1176/appi.books.9780890423349.

Bailey, A., Palferman, S., Heavey, L., & Le Couteur, A. (1998). Autism: the phenotype in relatives. Journal of autism and developmental disorders, 28(5), 369–392. https://doi.org/10.1023/a:1026048320785 

Bernier, R., Gerdts, J., Munson, J., Dawson, G., & Estes, A. (2012). Evidence for broader autism phenotype characteristics in parents from multiple-incidence autism families. Autism research : official journal of the International Society for Autism Research, 5(1), 13–20. https://doi.org/10.1002/aur.226.

Chown, N. (2019). Are the “autistic traits” and “broader autism phenotype” concepts real or mythical? Autism Policy and Practice. 2 (1), pp. 46-63.

Gerdts, J., & Bernier, R. (2011). The broader autism phenotype and its implications on the etiology and treatment of autism spectrum disorders. Autism research and treatment, 2011, 545901. https://doi.org/10.1155/2011/545901

Hurley, R. S., Losh, M., Parlier, M., Reznick, J. S., & Piven, J. (2007). The broad autism phenotype questionnaire. Journal of autism and developmental disorders, 37(9), 1679–1690. https://doi.org/10.1007/s10803-006-0299-3.  

Kadak, M. T., Demirel, O. F., Yavuz, M., & Demir, T. (2014). Recognition of emotional facial expressions and broad autism phenotype in parents of children diagnosed with autistic spectrum disorder. Comprehensive psychiatry, 55(5), 1146–1151. https://doi.org/10.1016/j.comppsych.2014.03.004.

Landry, Oriane & Chouinard, Philippe. (2016). Why We Should Study the Broader Autism Phenotype in Typically Developing Populations. Journal of Cognition and Development. 17. 584-595. 10.1080/15248372.2016.1200046. 

Piven J. (2001). The broad autism phenotype: a complementary strategy for molecular genetic studies of autism. American journal of medical genetics, 105(1), 34–35.

Rubenstein, E., & Chawla, D. (2018). Broader autism phenotype in parents of children with autism: a systematic review of percentage estimates. Journal of child and family studies, 27(6), 1705–1720. https://doi.org/10.1007/s10826-018-1026-3

Tan, D.W., Maybery, M.T., Gilani, S.Z. et al. (2020) A broad autism phenotype expressed in facial morphology. Transl Psychiatry 10, 7. https://doi.org/10.1038/s41398-020-0695-z

Support Autism Parenting Magazine

We hope you enjoyed this article. In order to support us to create more helpful information like this, please consider purchasing a subscription to Autism Parenting Magazine.

Download our FREE guide on the best Autism Resources for Parents

Related Articles

Autism Parenting Magazine