Quirkiness: The Broader Autism Phenotype #AtoZChallenge

Welcome to another week and another day in the A to Z Challenge on autism. Today’s post is called “Quirkiness” because I couldn’t think of any other relevant word starting with the letter Q. I bet other people have trouble with this letter too. I will focus on the broader autism phenotype, which basically describes people who are quirky. This post is quite involved, so I hope I have explained things properly.

The broader autism phenotype (BAP) describes people who have similar but milder traits than those found in autism spectrum disorder people, and who are not impaired in their functioning by these traits. The broader autism phenotype is particulalry useful for research into the heritability of autism. It is likely that autism is largely a genetic disorder, and this idea is supported by research into the BAP. Non-autistic parents of autistic children more often than parents of neurotypical children exhibit the broader autism phenotype.

So what is the broader autism phenotype? It describes traits that are related to autism and are more common among family members of autistic people. According to Losh et al. (2008), this includes characteristics such as a socially reticent or aloof personality, untactful behavior and fewer high-quality (ie. emotionally reciprocial) friendships. It also includes a rigid personality, little interest in novelty, difficulty adjusting to change and a perfectionistic or overly conscientious personality. Family members of autistic people also exhibit more fear or neuroticism and are at a higher risk of developing anxiety disorders.

Non-autistic parents’ autistic traits are, for research purposes, commonly measured by the broad autism phenotype questionnaire (BAPQ). The BAPQ focuses on the traits and behaviors I mentioned above.

Only 10% to 20% of cases of autism can be explained by a known biological cause, such as a genetic mutation (Sasson et al, 2013). These are often sporadic mutations, meaning they occur in the autistic person only and not their parents.

With the broad autism phenotype, autism symptoms do carry over from one generation onto the next. A large number of autistic children in a study by Sasson et al. (2013) had one parent who displayed the broad autism phenotype. If both parents displayed the BAP, a child was also more likely to be autistic than not. The presence of the broader autism phenotype was also associated with the severity of autistic symptoms. In other words, if one or both parents had autistic quirks, an autistic child was more likely to be more severely affected. Maxwell et al. (2013) found the same: a higher score on the BAPQ in parents was related to more severe autistic symptoms (as measured by the Social Responsiveness Scale) in their children. The parents’ BAPQ score was not related to the child’s IQ, which is a common measure of functioning level in autistics.


Losh M, Childress D, Lam KSL and Piven J (2008), Defining Key Features of the Broad Autism Phenotype: A Comparison Across Parents of Multiple- and Single-Incidence Autism Families. Am J Med Genet B Neuropsychiatr Genet, 147B(4):424-433. DOI: 10.1002/ajmg.b.30612.

Maxwell CR, Parish-Morris J, Hsin O, Bush JC, and Schultz RT, The Broad Autism Phenotype Predicts Child Functioning in Autism Spectrum Disorders. J Neurodev Disord. 2013; 5(1): 25. DOI: 10.1186/1866-1955-5-25.

Sasson NJ, Lam KS, Parlier M, Daniels JL, Piven J (2013), Autism and the Broad Autism Phenotype: Familial Patterns and Intergenerational Transmission. J Neurodev Disord, 5(1):11. doi: 10.1186/1866-1955-5-11.


3 thoughts on “Quirkiness: The Broader Autism Phenotype #AtoZChallenge

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