XYY Syndrome = Psychopathy?

As an enthusiast of true crime, one of the most interesting controversies in the realm of forensic psychology is associated with XYY syndrome, also known as Jacobs syndrome (named after Dr. Patricia Jacobs, the pioneering scientist who initially identified this disorder). XYY syndrome manifests in males possessing an additional Y chromosome, resulting in a karyotype of 47 XYY instead of the typical 46 XY configuration. Some characteristics include heightened stature, language developmental delays, motor impairments, behavioral and emotional difficulties, learning disabilities, and ADHD. Last year, I encountered an article exploring the potential link between XYY syndrome and psychopathy, specifically Antisocial Personality Disorder; for instance, individuals such as Robert Peter Tait, Daniel Hugon, and John Farley - all exhibiting an extra Y chromosome - had been implicated as serial killers. The earliest research shedding light on this topic can be traced back to the 1960s. Early researchers conducted research on male inmates who had an XYY chromosome constitution, discovering that a relatively high percentage of males in jail were carriers of XYY chromosome; they appeared to be taller and more aggressive in nature compared to their counterparts. Thus, some scholars claimed that the presence of an extra Y chromosome might be associated with aggressive behavior and criminal tendencies. Following this initial study, there was increased interest in the potential connection between XYY syndrome and criminality. Recent research has also corroborated the finding by establishing a connection between the diagnosis of XYY syndrome and convictions for criminal offenses (Stockholm, 2012).

However, subsequent research has yielded conflicting and inconclusive findings. For instance, certain researchers argued that the association is too arbitrary. The earliest skepticism regarding this link was expressed by Borgaonkar et al. in 1967, who contended that the unique personality characteristics should not be categorized as aggressiveness; instead, they coined the term "defective delinquents." Subsequent studies indicate that a majority of individuals with XYY syndrome do not exhibit criminal behavior and lead normal lives. A systematic review conducted by Re & Birkhoff in 2015 found no statistical evidence directly pinpointing a predisposition to antisocial behavior. Notably, there are numerous individuals with XYY syndrome who actually excel in their careers, including Jacob Hoggard, a Canadian musician; Lee Majors, a famous actor; and John Gapper, a business columnist for the Financial Times in England. 

Recently, a child-rearing reality TV show in Korea has caused an uproar. A young boy with an additional Y chromosome exhibited threatening behavior towards his mother. At an even younger age, his mother observed his volatile temperament, which not only manifested as bullying at school but also included daily physical abuse towards his mother. The footage from the TV show was rather graphic. However, instead of showcasing empathy, the audience berated the mother for her decision to give birth to her son. It was revealed that during pregnancy, despite facing opposition from doctors and family members due to societal stereotypes surrounding XYY carriers, the mother had been aware of her son's genetic condition through various examinations yet decided to proceed with childbirth regardless. Unfortunately, pregnant mothers carrying XYY babies often face discrimination from hospitals due to preconceived notions within the scientific community regarding the potential risks they may pose to society. However, it is important to note that a significant majority of individuals with an additional Y chromosome lead normal and law-abiding lives, and the presence of an extra Y chromosome alone does not predict criminal behavior. In my perspective, criminality represents a multifaceted phenomenon influenced by a combination of genetic, environmental, and social factors. The Ecological Theory proposed by Bronfenbrenner perfectly explains the complexity. Individuals who are XYY carriers are already susceptible to emotional and behavioral problems; thus they may be at a greater risk for criminality when exposed to adverse conditions within their various environmental systems. Conversely, positive influences and supportive environments can act as protective factors. It is often the interplay among these systems that shapes an individual's likelihood of engaging in criminal behavior. Consider the aforementioned TV show as an example; the boy grew up in a divorced family with an abusive father who harbored animosity towards him due to his disorder. His aggressive characteristics might have been triggered and even exacerbated by his father’s abuse. Additionally, his father consistently insinuated that he would inevitably become delinquent and eventually evolve into a serial killer as he was an XYY carrier. This might also lead to his violence as he internalized these expectations. In conclusion, it is imperative for society as a macrosystem to exhibit compassion and discard stereotypes not only towards individuals belonging to the XYY group but also other groups suffering from various genetic disorders.

References

Re, L., & Birkhoff, J. M. (2015). The 47,XYY syndrome, 50 years of certainties and doubts: A systematic review. Aggression and Violent Behavior, 22, 9–17. https://doi.org/10.1016/j.avb.2015.02.003

Stochholm, K., Bojesen, A., Jensen, A. S., Juul, S., & Gravholt, C. H. (2012). Criminality in men with Klinefelter's syndrome and XYY syndrome: a cohort study. BMJ open, 2(1), e000650. https://doi.org/10.1136/bmjopen-2011-000650

Welch, J., Borgaonkar, D. & Herr, H. Psychopathy, Mental Deficiency, Aggressiveness and the XYY Syndrome. Nature 214, 500–501 (1967). https://doi.org/10.1038/214500a0