A shortened, edited version of this essay appeared on Honours Review, a student journal for Honours students of the University of Groningen.
In the past decades, sex differences have garnered increasing scrutiny from psychological researchers. Despite this enthusiasm, sex differences are often erroneously assumed to be unimportant, small and unreliable (1). Yet, some psychological and behavioral phenomena show stable biases towards one sex that cannot be satisfactorily explained by differences in upbringing and socialization. The sex differences in psychopathology are striking, and can be utilized to understand sex-differential inclinations in neurotypical populations.
Many behavioral disorders are characterized by extreme forms of behaviors that are otherwise considered normal and can shed light on the drives that define the human mind. Psychopathology and developmental disorders differ greatly between males and females, as men and women are born with universal and stable predispositions that prepare them for different evolutionary purposes. The magnitude of the sex specific traits fluctuate on a continuum, not an all or none basis, and can therefore result in extreme, maladaptive expressions of sex typical tendencies. This differential prevalence of psychological conditions can offer us crucial insights into sex-specific tendencies and functionalities that might be decisive for forming certain disorders. This essay will compare the epidemiology of mental illnesses in both sexes, and suggest that many mental conditions are extreme expressions of sex specific inclinations that are present in nonclinical populations.
‘’it’s pretty difficult to find any single factor that’s more predictive for (psychiatric) disorders than gender’’ (2).
– Thomas Insel, head of the National Institute of Mental Health
[ the Extreme Male Brain Theory of Autism ]
In 1997, Simon Baron-Cohen introduced the extreme male brain theory of autism. This theory stipulates that the symptoms of autism embody extreme male traits (3). It introduced the proposition that some disorders are a result of brains that are too masculine. Autism spectrum disorder (ASD) is characterized by impaired social interaction, the inability to understand others, a weak theory of mind (ToM), narrow interests, and stereotyped, repetitive behaviors. People diagnosed with autism oftentimes excel in their narrow interests. Accordingly, individuals with Asperger’s syndrome, a high-functioning form of autism, were often called ‘’little professors’’ by Hans Asperger (4), due to their ability to memorize large amounts of information about a particular subject. A high interest in understanding systems is a striking feature of autism spectrum disorders.
The rationale behind the extreme male brain theory is that autistic individuals show an extreme form of sex differences seen in the nonclinical population. Neurotypical males are slightly impaired in empathizing compared to neurotypical females, but are usually better at systemizing (5). Baron-Cohen defines empathizing as the drive to identify another person’s emotions and thoughts, and to respond to these with an appropriate emotion. On the other hand, systemizing is the understanding of input/output relationships, such as understanding the rules of music, mechanics or computer programming (5). People with autism are severely impaired in regards to empathy but have an unusual ability to understand systems. A powerful tenet of this theory is that males and people with autism are over-represented in fields guided by systems, such as physics or music. Consequently, Baron-Cohen introduced the empathize/systemize dichotomy to define the female brain and the male brain. These sex differences are based on averages, and the theory concurs that autism can also be present in females. ASD is four times more prevalent in males than in females (6). In high-functioning autism, the male to female ratio is higher than 10:1 (5). Autism spectrum conditions constitute the phenotype of excessive brain masculinization, according to Baron-Cohen.
[ the extreme female brain ]
Baron-Cohen claims that excessive systemizing and insufficient empathizing characterize autism. But, what about people who have a low interest for systems, but have an unusually high drive to empathize? Logically, we would expect excess empathizing and inadequate systemizing to be undesirable as well. This would lead us to the female end of the spectrum. There are indeed disorders characterized by an excessive sensitivity to social relationships, which are primarily seen in females. For example, borderline personality disorder (BPD) and histrionic personality disorder (HPD) are both characterized by an abnormal drive for socialization. BPD is defined by instability of behaviors, interpersonal relationships, and self-image (7). Symptoms include sensitivity to rejection, fear of abandonment, self-harm, suicidal tendencies, quickly changing between idealizing and devaluating others, uncertainty concerning one’s own identity, intense sensitivity in relationships with others, and severe dissociation (8). People with BPD engage in potentially dangerous behaviors, such as substance abuse, promiscuous sexual behavior, hair coloring, tattooing, and piercing (9). BPD patients show weak autobiographical memory (8), constantly feel empty, have no self-concept outside of their relationships, experience imaginary victimization (10), and often do not know what they personally like, believe, value or prefer (11). Interestingly, although it is not part of the diagnostic criteria, BPD patients frequently lie and manipulate others, often to trick people into expressing sympathy for them. The female-to-male ratio in BPD is 3:1. By simple definition, BPD is a maladaptive pattern of behavior to fulfill an intense social need, often expressed by manipulative strategies to obtain nurturing attention.
A similar disorder is dissociative identity disorder (DID), mostly known under the name of multiple personality disorder. It is characterized by enduring distinct identities or dissociative states. Approximately half of those diagnosed with DID fit the criteria for BPD, as their diagnostic criteria overlap considerably (12). Lack of social support, reported childhood trauma, and disorganized attachment (both hating and adoring someone at the same time) are necessary components for a diagnosis of DID. Self-harm is a widespread occurrence in the DID population (13). Many people diagnosed with DID claim that child abuse marked the onset of their symptoms, but there is no evidence to support that claim (14). DID is nine times more prevalent in adult females than adult males (15).
An excessive sensitivity to interpersonal relations is not always as pervasive as in BPD, and can be seen in people that are less distressed, such as people with histrionic personality disorder (HPD). HPD is characterized by excessive attention seeking behaviors and a strong need for approval from others. People with HPD are loud, behave inappropriately, have an unstable personality, exaggerate their behaviors and emotions, are flirtatious, crave stimulation, and are easily influenced by others. People with HPD are usually promiscuous, parasitic, and manipulative. They are generally well-functioning and have good social skills, and frequently use them to be the center of attention, for instance by exaggerating symptoms of physical illness, dramatizing, behaving in sexually inappropriate ways, and exaggerating their difficulties. HPD is closely related to BPD, as both emerged from the discontinued diagnosis of hysteria. Some criteria for HPD have been removed from the DSM-III as it could not distinguish between HPD and BPD, such as craving for activity, irrationality, and manipulative suicidal attempts. Furthermore, both are overly dependent on the social environment, leading to naivety and suggestibility as defining characteristics. HPD affects women four times more than men (16). People with HPD usually do not struggle as much as people with BPD, but its female bias is nonetheless consistent with the view that females are overrepresented in conditions of immoderate need to empathize.
BPD and HPD can be seen as the extreme of the normal female profile, as it shows extreme forms of the higher need for empathizing in females (5). In addition, individuals with either condition have acute neuroticism (17), and neuroticism is the trait of the Big 5 Personality Traits that distinguishes best between men and women (18). Their intense social needs lead them to use harmful strategies to achieve their goals. This inflexible tendency to seek nurturing attention is best illustrated with their higher likelihood to use strategies to obtain comforting, such as factitious symptoms, false rape allegations, factitious claims of child abuse, conversion disorder, accusations based on repressed memories, and a myriad of other disabling phenomena for which there is no scientific evidence (including DID). BPD and HPD are certainly under-diagnosed in favor of these conditions. In an article published in June 2015, Baron-Cohen expressed a recommendation to continue considering people with BPD as having extreme female brain (19). The empirical test of this theory will most likely follow shortly, but the female preponderance in BPD and HPD is highly suggestive.
[ other candidates for the phenotypic expression of the extreme male brain ]
Earlier, I explored Baron-Cohen’s suggestion that autism was a result of extreme brain masculinization. There are, however, a number of disorders that are primarily seen in males which are strongly related to other masculine traits. This suggests that the Extreme Male Brain theory might not encompass all the possible phenotypes of the male brain, and that this shortcoming requires clarification. Here are additional disorders that are often linked to excess masculinity.
Antisocial personality disorder (ASPD), commonly known as psychopathy, is defined by enduring antisocial behavior, reduced empathy, bold behavior, and fearlessness. One quarter of the male prison population fits these criteria. Robert D. Hare, who developed the Hare Psychopathy Checklist, believes that psychopaths are relatively successful in the workplace, as psychopathic traits are common in higher positions of corporate organizations. Their boldness and propensity for risk-taking may be adaptive in executive functions, and even organized crime. The traditional phenotype of psychopathy, characterized by grandiose self-image and instrumental violence, is almost exclusively seen in males (20). Females diagnosed with antisocial personality disorder (psychopathy) show symptoms that are more accurately described by HPD and BPD, which are often diagnosed alongside of ASPD in females (20). Other than being highly male biased, psychopathy is strongly linked to correlates of hyper masculinity, such as aggression, sensation seeking, criminality, and testosterone. This suggests that autism might not encompass the whole range of the extreme male brain.
ADHD is a neurodevelopmental disorder characterized by hyperactivity, not listening when spoken to, struggling with instructions, frequently interrupting others, acting without considering the consequences, having difficulties waiting for their turn, having difficulties sitting still, squirming and fidgeting, and having impairments in social interactions and friendships. ADHD has three subtypes: inattentive, hyperactive/impulsive and combined. ADHD is often linked to hyper-masculinity, as it is often seen in traits and behavioral patterns that are often typically defined as masculine, such as drug and alcohol abuse, high spatial ability, conduct disorder, risk-taking activities, and physical injury. Interestingly, people with ADHD are overly represented in sports, as it has been theorized that 25% of athletes have hyperactivity disorder. ADHD is diagnosed three times more often in males than females, and males are treated nine times more than females, and in severe ADHD, the ratio is 16:1. The higher numbers of males with ADHD and its correlations to masculine traits challenges the Extreme Male Brain theory of autism.
Many have studied the link between ADHD and psychopathy and autism. Indeed, ADHD is often comorbid with either and its subtypes diverge in symptoms of psychopathy and autism. Specifically, the symptoms of the inattentive subtype resemble those of autism, and those of the hyperactive and combined subtype resemble
psychopathy. ADHD and autism both share the symptoms of low attentiveness to social cues, communication problems and narrow interests. Indeed, language delays, difficulty in listening when spoken to, missing social cues, difficulty processing nonverbal and verbal language, and the inability to concentrate on material that is not personally interesting are all symptoms shared by sufferers of ADHD and autism. ADHD is also linked to a weak theory of mind (21) and repetitive behaviors (22) which are the core components of ASD. Furthermore, ADHD is, like autism, highly comorbid with Tourette’s syndrome. ADHD and psychopathy are both characterized by the persistent breaking and defying of social norms, impulsivity, impatience, acting without regard to the consequences, impulsive behavior, substance abuse, and proneness to boredom. Some have argued that people with ADHD have psychopathic traits, but to a subclinical extent (23). Additionally, the inattentive symptoms correlate negatively with the hyperactive symptoms, indicating the psychopathic traits and autistic traits correlate negatively in those with ADHD, indicating that psychopathy and autism represent two ends of a spectrum. In short, people with ADHD show symptoms of autism, notably in their narrow interests and social deficits, and also have mild psychopathic traits, as seen in their impulsive and sensation-seeking tendencies. Does the continuum from autism, to ADHD, to psychopathy represent the male end of excess masculinization?
It appears not, according to current assumptions about the male brain. It is unlikely that psychopaths have an extreme male brain, as they are usually reasonably well functioning socially. As a matter of fact, psychopaths have an intact theory of mind (24) and decent emotion recognition skills for most emotions, unlike individuals with autism. Even though psychopathy is strikingly sex biased and it might seem like an indicator of an extreme male brain, psychopathy has been linked to elevated intrapersonal power, and men and women use this power differently. In a similar vein, people with ADHD experience a decrease in their symptoms over time and about 40% will have no enduring symptoms in adulthood, even though their social cognition is mildly impaired. These conditions show sex-specific behaviors and their epidemiology is biased towards males, but they do not have the burdensome symptoms that individuals with autism have. Therefore, if the extreme male brain is characterized by the absence of a theory of mind, autism spectrum disorders represent the extreme expression of sex specific traits more accurately. Yet, ADHD and psychopathy can be considered as excessively masculinized behavioral tendencies.
[ what defines both extremities of the spectrum? ]
Females are vastly over-represented in adolescent-onset emotional disorders involving shallow self-concepts, extreme neuroticism, dissociation and excessive social needs (25). Such social need often expresses itself in manipulative strategies to evoke nurturance, by self-harm, imagined victimization or factitious symptoms (26). Yet, it is unclear how dissociation and empathic needs relate to each other. Females consider others as representing a larger part of their identity, compared to males (27). Accordingly, those with an extremely female brain might have a self-concept that is almost entirely characterized by their relationships with others, at the cost of not having a stable, durable identity, and personal interests. This might lead to a point where their fragile sense of self makes them vulnerable to dissociation due to a complete abandonment of one’s identity. Empathy would come at a cost that would contrast with the narrow interests and autonomy that people with autism have. To determine the validity of this theory, further consideration is needed. A possible first step would be to explore the empathizing/systemizing scores of individuals with dissociative disorders to establish if they score lower on systemizing than average females. That would indicate that they have an extremely female brain. If this is the case, the term empathy would seriously need reconsideration, as both histrionic and borderline personality disorders have been argued to constitute the female phenotype of psychopathy (28, 29).
Males make up the large majority of those diagnosed with early-onset neuropsychiatric disorders that involve a lack of conformity to social norms and antisocial behavior (25). These disorders are all strongly linked to impairments in socialization. Consequently, lack of empathy does appear to define the male brain. More specifically, if a deficient ToM represents an extreme form of a lack of empathy, autism would be the phenotype of an extreme male brain. Yet, some ambiguity remains. For instance, there has been a recent increase in autism diagnoses in females. While they do not show the typical phenotype of autism, their impairments in social cognition are substantial. Most notably, people with borderline personality disorder, who have been theorized to have an extreme female brain, have impaired emotion recognition, which is characteristic of a deficient theory of mind. This suggests that the deficient theory of mind is not exclusive to the male brain, and it would be premature to exclude ADHD and psychopathy as potential expressions of excess masculinity on the basis of their functional theory of mind. Another point that needs to be addressed is that many correlates of the male brain do not appear to be linked to autism. In spite of the strong relationship between masculinity and spatial abilities, athletic abilities, aggression and sensation seeking, people with autism show none of these inclinations. In contrast, psychopaths and hyperactive people show these tendencies. As a result, people with ADHD and psychopathy are over-represented in sports and executive positions, respectively. One might argue that the definition of systems should be extended to include physical and professional fields, which are systems vastly dominated by males. In this way, the reasoning that was used to nominate autism as an extreme form of male traits could be extended to ADHD and psychopathy. Consequently, the hypothesis that autism, ADHD and psychopathy are all different phenotypes of the extreme male brain deserves empirical evaluation.
[ conclusion ]
The differential prevalence of mental conditions suggests that we are all on a continuum from poorly socialized to overly socialized. As psychological disorders represent maladaptive strategies to fulfill a need, they can offer us tools to determine the nature of the needs that define us. Females are over-represented in disorders characterized by an excessive social need, and males make up the majority of those with disorders characterized by poor socialization and a need to manipulate systems. To this day, the best candidates for the phenotypical expression of the extreme male brain are autism spectrum disorders, attention deficit and hyperactivity disorder and psychopathy, and borderline personality disorder (and its ramifications) and histrionic personality disorder for the extreme female brain. These sex-differential inclinations offer an unprecedented parallel with different evolutionary purposes in men and women, which are generating material and social capital respectively. A certain flexibility in systemizing needs and sociability is a healthy compromise, as people with an excessive social need, just like those who are overly antisocial, experience (and cause) considerable distress. These disorders represent extreme and inflexible forms of normal tendencies, and should not be marginalized, as they help us understand the proclivities that define all of us.
[ references ]
1. Cahill, Larry. 2006. “Why Sex Matters for Neuroscience.” Nature Reviews. Neuroscience 7 (6): 477-484.
2. Holden, Constance. 2005. “Sex and the Suffering Brain.” Science 308 (5728): 1574.
3. Baron-Cohen, Simon. 1997. “Is Autism an Extreme form of the ”Male Brain”?” Advances in Infancy Research 11: 193-217.
4. Frith, Uta, J. Morton, and A. M. Leslie. 1991. “the Cognitive Basis of a Biological Disorder: Autism.” Trends in Neuroscience 14 (10): 433-438.
5. Baron-Cohen, Simon. 2002. “The Extreme Male Brain Theory of Autism.” TRENDS in Cognitive Sciences 6 (6): 248-254.
6. Fombonne, Eric. 2003. “Epidemiological Surveys of Autism and Other Pervasive Developmental Disorders: An Update.” Journal of Autism and Developmental Disorders 33 (1): 365-382.
7. Gunderson, John G. 2011. “Borderline Personality Disorder.” The New England Journal of Medicine 364: 2037-2042.
8. Jones, B., H. Heard, M. Startup, M. Swales, J.M. Williams, and R.S. Jones. 1999. “Autobiographical Memory and Dissociation in Borderline Personality Disorder.” Psychological Medicine 29 (6): 1397-1404.
9. D’Ambrosio, Antonio, Nicoletta Casillo, and Valentina Martini. 2014. “Piercings and Tattoos: Psychopathological Aspects ” Activitas Nervosa Superior Rediviva 55 (4): 143-148.
10. Zanarini, M.C., F.R. Frankenburg, C.J. DeLuca, J. Hennen, G.S. Khera, and J.G. Gunderson. 1998. “The Pain of being Borderline: Dysphoric States Specific to Borderline Personality Disorder.” Harvard Review of Psychiatry 6 (4): 201-207.
11. Simeon, Daphne and Jeffrey Abugel. 2008. Feeling Unreal: Depersonalization Disorder and the Loss of the Self.
12. Simeon, Daphne. “Dissociative Identity Disorder.” Merck, accessed August 5, 2015, http://www.merckmanuals.com/.
13. Seligman, Martin EP, Elaine F. Walker, and David L. Rosenhan. 2000. Abnormal Psychology. 4th Ed.
14. Giesbrecht, Timo, Steven J. Lynn, Scott O. Lilienfeld, and Harald Merckelbach. 2008. “Cognitive Processes in Dissociation: An Analysis of Core Theoretical Assumptions.” Psychological Bulletin 134 (5): 617-647.
15. Sno, H. N. and H. F. Schalken. 1999. “Dissociative Identity Disorder: Diagnosis and Treatment in the Netherlands.” European Psychiatry 14 (5): 270-277.
16. American Psychiatric Association. 2013. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Washington, DC.
17. Clarkin, John F., James W. Hull, Jennifer Cantor, and Cynthia Sanderson. 1993. “Borderline Personality Disorder and Personality Traits: A Comparison of SCID-II BPD and NEO-PI.” Psychological Assessment 5 (4): 472-476.
18. Schmitt, David P., Martin Voracek, Anu Realo, and Juri Allik. 2008. “Why Can’t a Man be More like a Woman? Sex Differences in Big Five Personality Traits across 55 Cultures.” Journal of Personality and Social Psychology 94 (1): 168-192.
19. Larson, Felicity V., Meng-Chuan Lai, Adam P. Wagner, MRC AIMS Consortium, Simon Baron-Cohen, and Anthony J. Holland. 2015. “Testing the ‘Extreme Female Brain’ Theory of Psychosis in Adults with Autism Spectrum Disorder with Or without Co-Morbid Psychosis.” PloS One 10 (6): 1-14.
20. Wynn, Rolf, Marita H. Hoiseth, and Gunn Pettersen. 2012. “Psychopathy in Women: Theoretical and Clinical Perspectives.” International Journal of Women’s Health 4: 257-263.
21. Uekermann, J., M. Kraemer, M. Abdel-Hamid, BG Schimmelmann, J. Hebebrand, I. Daum, J. Wiltfang, and B. Kis. 2010. “Social Cognition in Attention-Deficit Hyperactivity Disorder (ADHD).”Neuroscience and Biobehavioral Reviews 34 (5): 734-743.
22. Rutter, Michael. 2014. “Factor Structure of Autistic Traits in Children with ADHD.” Journal of Autism and Developmental Disorders 44 (1): 204-215.
23. Fowler, Tom, Kate Langley, Frances Rice, van den Bree, Marianne B.M., Kenny Ross, Lawrence S. Wilkinson, Michael J. Owen, Michael C. O’Donovan, and Anita Thapar. 2009. “Psychopathy Trait Scores in Adolescents with Childhood ADHD: The Contribution of Genotypes Affecting MAOA, 5HTT and COMT Activity.” Psychiatric Genetics 19 (6): 312-319.
24. Richell, R.A., D.G.V. Mitchell, C. Newman, A. Leonard, S. Baron-Cohen, and R.J.R. Blair. 2003. “Theory of Mind and Psychopathy: Can Psychopathic Individuals Read the ‘language of the Eyes’?” Neuropsychologia 41: 523-526.
25. Rutter, Michael, Avshalom Caspi, and Terrie E. Moffitt. 2003. “Using Sex differences in Psychopathology to Study Causal mechanisms: Unifying Issues and Research Strategies.” Child Psychology and Psychiatry 44 (8): 1092-1115.
26. Krahn, Lois E., Hongzhe Li, and M. Kevin O’Connor. 2003. “Patients Who Strive to be Ill: Factitious Disorder with Physical Symptoms.” American Journal of Psychiatry 160 (6): 1163-1168.
27. Cross, S. E. and L. Madson. 1997. “Models of the Self: Self-Construals and Gender.” Psychological Bulletin 122 (1): 5-37.
28. Cale, Ellison M. and Scott O. Lilienfeld. 2002. “Histrionic Personality Disorder and Antisocial Personality Disorder: Sex-Differentiated Manifestations of Psychopathy?” Journal of Personality Disorders 16: 52-72.
29. Sprague, Jenessa, Shabnam Javdani, Naomi Sadeh, Joseph P. Newman, and Edelyn Verona. 2012. “Borderline Personality Disorder as a Female Phenotypic Expression of Psychopathy?” Personal Disorders 3 (2): 127-139.