36 Chapter 2 Neuroendocrinology of psychopathy Research on the neuroendocrinological underpinnings of psychopathy suffers from small sample sizes, especially for individuals scoring high on the psychopathy checklist, and also from lack of one clear definition of the different subtypes of psychopathy (Brazil et al., 2016; Koenigs, Baskin-Sommers, Zeier, & Newman, 2011). One of the few studies with psychopathic offenders (n = 17) featuring the AAT indicates that this maladaptive behavior already stems from early automatic mechanisms by showing reduced avoidance tendencies towards angry faces compared to healthy control participants (n = 15) (von Borries et al., 2012). In addition, this effect was related to higher levels of instrumental aggression and reduced feelings of discomfort when observing another’s negative experiences. Neuroimaging studies of psychopathic offenders show structural deviations in several brain areas, including reduced amygdala and prefrontal volume, increased striatal volume, and an abnormal shape of the hippocampus (Koenigs et al., 2011). In addition, psychopathy is associated with impaired amygdala–prefrontal connections in a relatively small sample (n = 22) and a larger sample (n = 147); (Hoppenbrouwers et al., 2013; Wolf et al., 2015, respectively). On a functional level, the amygdala seems to respond less to aversive stimuli, fearful faces, and pictures of moral violations (Anderson & Kiehl, 2012; Decety, Chen, Harenski, & Kiehl, 2015, n = 155), in addition to atypical activity of the aPFC during various tasks. Interestingly, striatal activity is enhanced, suggesting an increase in reward sensitivity (Van Honk & Schutter, 2006). During the control of social approach– avoidance behavior, psychopathic offenders (n = 15) show reduced anterior prefrontal cortex activity and less anterior prefrontal cortex–amygdala connectivity (versus 19 healthy controls), and this was modulated by endogenous testosterone levels (Volman et al., 2016). These findings suggest that higher testosterone levels are associated with less prefrontal control over amygdala-driven actions. Because of its social dominance-promoting effects, including dampening of punishment sensitivity and increasing reward sensitivity, testosterone has been in the picture with regard to the biological underpinnings of psychopathy. Psychopathy is associated with social dominance (Lobbestael, Arntz, Voncken, & Potegal, 2018). Studies yielded mixed results in trying to relate endogenous testosterone to psychopathy scores (e.g., Glenn et al., 2012, n = 178; Welker, Lozoya, Campbell, Neumann, & Carré, 2014), and rather found relationships with typical personality traits associated with psychopathy, such as impulsivity and antisocial aspects (Stålenheim, Eriksson, von Knorring, & Wide, 1998, n = 61). Importantly, several studies showed that the relation between testosterone and psychopathy was modulated by cortisol (Glenn et al., 2012; Loomans, Tulen, de Rijke, & van Marle, 2016; Welker et al., 2014, sample sizes were respectively 178, 166, 237). A combination of high testosterone levels and low cortisol levels tends to be associated
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