MAOA and male antisocial behavior: A review
Introduction
Of all the risk factors for the development of antisocial behavior, “maleness” is by far the most robust predictor (Tremblay, 2008). Among the numerous biological factors that have been identified as increasing risk for antisocial behavior (Van Goozen & Fairchild, 2008), one of the most well-supported has inexplicably received very little attention with regard to implications for explaining why maleness is such a robust predictor of antisocial behavior. That factor is the low activity form/allele of the monoamine oxidase-A gene (MAOA-L) which arguably represents the clearest link between a genetic variation and antisocial behavior (Dodge, 2009, Meyer-Lindenberg et al., 2006, Raine, 2008). A major reason for this inattention to the MAOA-L gene may be the failure to appreciate that its location on the X chromosome reflects the enormous biological disadvantage of the male compared to the female (Migeon, 2007).
This article, after presenting a brief overview of the research which establishes that MAOA-L is one of the most well-supported biological risk factors for antisocial behaviors, such as aggression and conduct problems, will discuss how the enormous male biological disadvantage relates to the sex difference in the prevalence of MAOA-L and thus helps explain why maleness is the most robust predictor of antisocial behavior.
Section snippets
MAOA
Although studies of aggressive behavior in animals and humans had long implicated altered metabolism of serotonin, it was not until 1993 that a specific genetic variant implicated in this alteration was identified (Brunner, Nelen, Breakefield, Ropers, & van Oost, 1993). This variant was MAOA-L. MAOA is a gene on the X chromosome which codes for the enzyme monoamine oxidase A and is expressed throughout the brain (Shih et al., 1999, Viding and Frith, 2006). This enzyme degrades the monamimes,
Males at an enormous biological disadvantage compared to females
As previously mentioned, the MAOA gene is located on the X chromosome and therefore can be expected to follow the classic principles of X-linked gene expression. These principles place males at an enormous biological disadvantage compared to females (Migeon, 2007).
Greater male vulnerability to MAOA-L
The generalized greater male vulnerability to a host of diseases and disorders extends to be greater male vulnerability to the low activity genotype MAOA. Since MAOA is an X-linked gene, this will result in males having two “straightforwardly characterized” genotypes: high activity if the gene is MAOA-H or low activity if the gene is MAOA-L (Caspi et al., 2002). The best estimate for the frequencies of these genotypes, as well as those of females, comes from Caspi et al. (2002) that constitutes
Conclusion
An important, largely overlooked biologically based reason for “maleness” being by far the most robust predictor of antisocial behavior is that males are, by far, more vulnerable to the effects of the clearest link between a genetic variation and antisocial behavior — the gene variant MAOA-L. Namely, males are three times more likely than females (37% vs. 12%) to have this genotype, which in interaction with various forms of psychosocial adversity such as maltreatment, increases their risk for
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2015, International Journal of Law and PsychiatryCitation Excerpt :Males are three times more likely than females (37% vs. 12%) to have this genotype. The remaining 88% of females are far less vulnerable than males, because they either have the MAOA-H genotype (42%) or they have a heterozygous genotype (42%; Buckholtz & Meyer-Lindenberg, 2008; Eme, 2013; Sjöberg et al., 2007). Although the structural and functional brain differences in both sexes with MAOA-L are broadly comparable, the resulting phenotype is different.
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