Elsevier

Medical Hypotheses

Volume 82, Issue 5, May 2014, Pages 615-618
Medical Hypotheses

Expanding upon the ‘extreme male brain’ theory of autism as a common link between other major risk factors: A hypothesis

https://doi.org/10.1016/j.mehy.2014.02.020Get rights and content

Abstract

On average, males have a stronger preference for physical systems and machines over interpersonal interactions; they have lower average levels of cognitive empathy or social cognition than females; and they have higher rates of ‘extreme’ intelligence when it comes to abstract concepts such as those found in mathematics and sciences. All three traits are also commonly associated with individuals with an autism spectrum disorder or ASD; clearly, it is not coincidental that incidence rates of autism are reportedly four times higher in males than in females.

The common link between the majority of risk factors assessed in this review (including technological advancements, advanced parental age, socioeconomic status, and genetic predispositions towards ASDs in families of scientists and engineers) can be traced to a specific hormone, testosterone. It was established that traits which are typically associated with males are also typically associated with ASDs as well as individuals with antisocial personality disorder, or APD. The key distinction between individuals who are considered to be ‘autistic’ as opposed to those who are considered ‘sociopathic’ lies in the difference between their empathy deficits: whereas those who are ‘autistic’ are said to lack cognitive empathy (the ability to identify and understand the thoughts and feelings of others and to respond to these with appropriate emotions), those who are ‘sociopathic’ are said to lack emotional empathy (which is responsible for inhibiting acts of physical aggression or violence). This would explain why autistic individuals can have elevated testosterone levels without becoming physically aggressive.

Introduction

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by obsessive compulsions/interests, an extremely rigid or narrow way of thinking, and repetitive or ritualistic behaviour patterns. Depending on the level of severity, an affected individual may also possess intellectual and/or communicative deficits. All individuals on the spectrum are considered to possess deficits in cognitive empathy or social cognition and share a fundamental lack of understanding of basic social norms. Although autism is a life-long condition, in some cases early intervention and treatment can help improve functioning level and quality of life for the affected individual. Since children and adults with autism generally have good physical health and lack any kind of physical abnormalities, it is not possible to perform prenatal diagnostics for autism using the current screening technology (traditionally used to detect for other congenital disorders such as Down’s syndrome). This can in turn result in significant emotional, psychological, as well as financial repercussions for the parents and family of the affected individual.

In recent years there has been a noted rise in the prevalence of ASDs across the developed world. This has been attributed in part to increased awareness as well as broadening of the definition of symptoms to meet the criteria for a diagnosis, which has caused increasing numbers of individuals to receive an ASD diagnosis. It is also suspected that a rise in technological/societal risk factors can be linked to the increased prevalence of ASDs; for example, in a study of all 2.5 million births which occurred in California from 1996 to 2000, a total of ten autism ‘clusters’ (areas where the condition is significantly more common than elsewhere) were revealed [1]. The most concentrated of these ‘clusters’ was discovered in Santa Clara County, located in Silicon Valley (home of the world’s largest technological corporations as well as thousands of smaller start-up companies), indicating that areas with a large technological industry may be more conducive to attracting an ‘autism gene pool’. Furthermore, a 1998 study by Simon Baron Cohen showed that cases of autism were up to six times more prevalent among families of students who specialized in mathematics and sciences at degree level than in families of students who specialized in literature [2]. Although there may be many more unknown variables which contributed to these results, the correlation between ASDs and knowledge of abstract concepts such as those found in mathematics and sciences is prominent enough to warrant further investigation.

Section snippets

Hypothesis

The ‘extreme male brain’ theory, initially proposed by Simon Baron Cohen, suggests that the root cause of autism actually lies in prenatal exposure to excess levels of testosterone [3]. In this review, we wish to expand upon Cohen’s original work by establishing the extreme male brain theory as not only the most substantiated risk factor for ASDs, but also as a common link between other major risk factors (including technological, socioeconomic, and biological factors).

The hormonal link between

The dominant sex

While traits which are typically associated with males (such as having a strong preference for physical systems and machines over interpersonal interactions, decreased levels of cognitive empathy or social cognition, and emotional detachment) are also characteristic of individuals with an ASD, the same cannot be said for any of the ones typically associated with females (which are the opposites of the aforementioned traits). On this basis alone, there is a strong argument for the correlation

Discussion

Mental illness implies hormonal imbalances in the brain which causes normal levels to be dysfunctional. A mental disorder is characterized by normal traits of humans which are taken to a pathological extent or ‘extreme’. In this context, the ‘extreme male brain’ is a result of traits typically associated with males which are taken to a pathological extent so that the affected individuals are considered to be ‘autistic’ or ‘sociopathic’. Of all the possible risk factors for ASDs which have been

Conflicts of interest

None declared.

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