Broader Autism Phenotype

two boys

The concept of a broader autism phenotype is a source of controversy within the autism community. The controversy is largely due to its support for a possible genetic cause of autism. What exactly is a broader autism phenotype and how does it support the argument for a genetic connection to autism?

Broader Autism Phenotype Overview

The term broader autism phenotype (BAP) refers to a set of traits in people who show autistic type tendencies such as problems with language, communication and social skills but do not fit the DSM IV-TR diagnostic criteria for autism.

People who fit the BAP description are not diagnosed with autism but may have diagnosed autistic relatives, even in the immediate family. The theory is that people within the BAP range are more likely to have children or siblings with autism. The BAP theory supports the argument for a possible genetic cause of autism.

Family members of people with autism who fit a BAP show mild versions of autism symptoms. Autism characteristics in BAP may include:

  • Socially awkward or problems making friends
  • Problems understanding social cues
  • Prefers orderly routines
  • Obsessive behaviors


BAP should not be confused with pervasive developmental disorder not-otherwise-specified (PDD-NOS). PDD-NOS is a neurological condition that is part of the autism spectrum and affected people fit DSM IV-TR diagnostic criteria. BAP describes the appearance of a nonautistic person whose observable traits are similar to autism characteristics but has relatives with autism.

Families With Multiple Autistic Relatives

A 1997 University of Iowa study published in the American Journal of Psychiatry found that there are higher rates of social, communication, language and obsessive behaviors in the relatives of families with multiple cases of autism. 25 families with more than one child with autism were compared to 30 families with a child diagnosed with Down Syndrome.

This study claims to be the first to examine BAP by studying relatives in multiple incidence autism. The American Journal of Psychiatry study also quotes a University of Utah study that found that the risk of autism recurrence among siblings in families is up to 200 times the risk than in the general population.

Autism and Genetics

Does BAP prove that there is genetic link to autism? The evidence of multiple occurrence autism in families with nonautistic relatives who exhibit mild autism symptoms suggests a possible genetic connection. While there are many theories about potential causes of autism ranging from brain abnormalities to environmental factors with supporting scientific studies, the actual cause of autism unknown. In this regard, a genetic connection is one of many possible autism causes.

Some autism experts strongly support one potential cause over other theories, which can lead to many debates within the autism community. For example, experts who believe that autism is caused by environmental toxins may reject a proposed genetic connection. During the recent Vaccine Court ruling, some experts who supported the ruling pointed out that money should be spent on researching possible genetic causes of autism instead of researching connections between autism and vaccinations. Despite the many strong opinions on possible autism causes, autism research is still looking for the true cause of autism, one that can be irrefutably proven by scientific evidence.

Autism expert Dr. Joseph Piven was one of the 1997 University of Iowa study researchers. Piven has written articles on BAP in the American Journal of Psychiatry and the American Journal of Medical Genetics and given lectures on BAP. Piven's work on BAP provides evidence that the existence of BAP in relatives of families with autistic children demonstrates a genetic liability for autism.

Piven recommends the further study of BAP to determine possible genetic connections to autism and help identify groups of genes that, when present together, may produce autism.

Recent Autism Genetic Studies

Other studies have pointed toward possible genetic connections to autism. A 2009 University of Cambridge study identified 27 genes that may be associated with autism or Asperger's syndrome. A Danish study found that many children with autism had a history of autoimmune disease in their immediate families. These are just two of many studies that provide evidence to suggest a possible genetic cause of autism.

The Role of Genetics

The existence of BAP raises the question about the role of genetics in autism. Some experts would say that genes must play a role while others would argue that an environmental toxin may still be the autism trigger. More research is necessary to determine a definitive answer. Autism research is ongoing and each study is a step closer to a possible cause and cure for autism.

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