The article that first caught my eye was Stalenheim’s (2003). In years prior, little effort has been made in investigating the influence of thyroid hormones on personality, but there is understanding that higher levels of the T3 thyroid hormone (triiodothyronine) may be indicative of frequent criminality. Stalenheim was also aware that decreased monoamine oxidase (MAO) B activity signifies higher impulsivity, attention seeking, and aggressive behaviors. Based on these indications from previous findings, Stalenheim wanted to further explore whether T3, T4, and platelet MAO activity can be considered expressive, genetic predispositions for psychopathy and antisocial personality disorder. Additionally, she wanted to examine whether there were similar personality characteristics between participants and whether these traits could be considered genetic markers.
Stalenheim’s study consisted of 60 male subjects from the ages of 18-56 that were convicted for committing serious, in most cases violent, crimes. Of the subjects, none were psychotic, but all were diagnosed with at least one personality disorder by the DSM-III-R Axis I and/or Axis II. Disorders included substance abuse and dependence, a range of anxiety disorders, and antisocial personality. Blood samples were taken for hormone T3, T4 and platelet MAO analysis. The Karolinska Scale of Personality (KSP) ratings were obtained from 58 of the participants. The KSP measures stability of temperament traits in personality. The use of this scale determined stable traits among participants in relation to biological markers that would demonstrate a susceptibility to psychopathic characteristics. In addition to the KSP, the psychopathy checklist-revised (PCL-R) was also used. The scale focused on two factors, “selfishness, callousness and remorseless use of others” (Factor 1) and “chronically unstable and antisocial lifestyle and social deviance” (Factor 2).
Criminal recidivism was measured after these tests. Information on new prosecutions was provided and the type of crime was taken into account. Results showed a strong relationship between psychopathy, as assessed by the PCL-R, and criminal recidivism. In other words, those who committed crime again, most specifically violent crime, were more likely to show higher PCL-R scores than non-recidivists. The study population as a whole had higher levels of T3 and decreased levels of free T4 compared with the “normal controls.” PCL-R scores did not show a relationship between T3 levels and psychopathy. However, these hormone levels did show correlative data between psychopathy and aggression by the KSP. In addition, the scale recognized specific personality traits in relation to increased T3 levels as significant in reoffenders, but not in non-recidivists. These traits include impulsivity, socialization, irritability, and detachment. As expected, participants with the highest levels of T3 reverted back to law breaking.
Additionally, Stalenheim found that the lower the MAO activity was in violent reoffenders, the higher their scores were on the KSP for psychotic and aggressive traits. Interestingly, this association was not found between non-violent reoffenders and non-recidivists. In other words, MAO activity in relationship to the KSP for these specific factors seems to show significant data for those who are both violent and who have reoffended, but not in nonviolent reoffenders and non-reoffenders; the lower the MAO activity, the higher their scores correlated on psychopathy and aggressive factors, suggesting that low MAO activity may be contributive to psychopathic tendencies.
According to this research study, Stalenheim was able to reveal T3 levels and MAO activity and their influence on criminality. This study also supported criminality and its connection with aggression and various psychopathic traits based on T3 and MAO activity levels, but by the KSP. The persistence and stability of these levels and activity were found to be stable over time by the scales, suggesting they may be considered as biological markers of psychopathy, which supported Stalenheim’s hypothesis. These study results correlate with those briefly mentioned in the lay article, though they are somewhat varied in finding. As was seen, the PCL-R and KSP showed varied results where T3 levels showed significance by the KSP scale, but not the PCL-R. This could be because the PCL-R has advantages in foretelling criminal re-offenses, and results between people who had high versus low scores may have shown similar scores between Factor 1 and 2, suggesting an abnormal distribution of item factors. Meanwhile, the KSP examines personality traits that are more “normally distributed.”
It is most important to note that the extension of these findings to the general population and other people with traits outside the realm of psychopathy and antisocial personality may be done, but findings cannot necessarily be generalized without further examination. This study in particular can only be generalized to similar people as the participants studied. Further testing is probably required in order to really make any solid inferences, especially on those thyroid hormone levels because of the variation seen between the PCL-R and KSP scores.
As a whole, I believe this study accurately depicts the importance of T3 levels and MAO activity in the consideration of psychopathy, exposes researchers to some new implications for further studies, and fittingly urges the importance of doing so. The more that is revealed about the differing brain chemistries in individuals with the so-called biological markers of psychopathy, the more understanding we obtain of these sorts of people, and perhaps the more we can challenge for the prevention of their antisocial behaviors. Ways in which to mediate T3 and MAO activity levels may be beneficial.
It is crucial to note that these hormones are not the only contributors, as psychopathy, like any other in the field of psychology, has many contributors. With that said, Glenn, Raine, Schug, Gao, and Granger (2010) presented a new idea that testosterone and cortisol levels may have influences on antisocial behaviors in an interconnected way in which they are acting in accordance with response to each other. Testosterone, a product of the hypothalamus-pituitary-gonadal (HPG) axis, is known for regulating approach and reward seeking behaviors, so it is not in question that testosterone may be a contributor of the inability of psychopaths to inhibit certain approach behaviors. In addition to the HPG axis, the hypothalamus-pituitary-adrenal (HPA) axis is suggested to be often under stimulated in those who demonstrate psychopathic tendencies. This means their ability to experience fear, be aware and have concern for punishment, and initiate withdrawal behaviors in situations may be deterred due to this under stimulation. Researchers in this study were especially concerned with cortisol levels of the HPA axis.
Hormone researchers have barely skimmed the surface in the examination of hormone systems working together to contribute to behavior, aside from hormone systems and their individual contributions. From this limited amount of understanding, Glenn and Raine sought to not only examine the interaction between cortisol and testosterone levels, but to test whether these levels work together in ratio to each other to contribute to the antisocial, aggressive behaviors seen in psychopathy. The study used 178 adults, 156 men and 22 women, between the ages 18 and 45. Psychopathy was assessed with the PCL-R.
Saliva samples were taken in the morning of two consecutive days between 15-minute intervals and were later tested for cortisol levels. These values were averaged. In the afternoon, four saliva samples were collected between 20-minute intervals and two stressor tasks were provided to participants. The first sample tested for levels of cortisol before the stressor tasks, the second and third sample tested the response of cortisol to the stressor tasks, and the last sample tested cortisol levels after the tasks were implemented.
Of these two stressor tasks, one had an uncontrollable stressor and the other had a socially relevant stressor. Participants performed a countdown task where they would see numbers counting down from 12-0 on a screen. At the end of this countdown, a loud noise was presented (the uncontrollable stressor). The second stressor asked participants to give a 2-minute speech on the worst thing they had ever done with a proctor in the room videotaping. Results did not show a relationship between testosterone and cortisol levels with psychopathy scores according to the PCL-R. Overall, cortisol level increase to stressor tasks was only apparent in 35% of participants. This led researchers to divide their participants among those who did show cortisol level increases and those who did not. Those who did not show a cortisol response to the stressor tasks scored higher on psychopathy. This may suggest that those with psychopathic tendencies may show less cortisol response to stressful events than a normal person.
In addition, researchers did not find significant evidence that the ratio of at rest testosterone and at rest cortisol levels were indicators of psychopathy. However, they did find an association between at rest levels of testosterone and cortisol reaction levels to this testosterone with psychopathy, supporting the interwoven character of hormone systems in predicting antisocial behaviors. Researchers also tested to see whether the number of antisocial personality symptoms the offender had and the number of violent offenses reported by the offender were associated with the ratio score; they did not find any associations. On top of that, they tested the interaction between baseline testosterone and the ratio score in predicting psychopathy to see whether different levels of testosterone paired with cortisol reactivity showed variance. It seemed that higher levels of baseline testosterone paired with cortisol reactivity to those levels were most apparent in individuals who scored higher in psychopathy and had a higher ratio score in comparison to those with lower levels of testosterone that exhibited psychopathic traits seemed to be unrelated to the ratio score. This means that even though psychopathy traits were seen in those with both higher and lower levels of testosterone, it was only a relative predictor for those higher levels of testosterone in relation to cortisol reactivity and that differences in levels of baseline testosterone do in fact play a role when paired with cortisol reactivity levels.
Since they found that higher levels of testosterone in relation to cortisol reactivity is instrumental in determining higher psychopathy scores, it may be fair to say that the amygdala may be testosterone-driven. With that in mind, if testosterone levels are higher, contributing to a higher ratio of these levels with cortisol reaction, these higher levels may be indicative of amygdala malfunction in gauging the consequences of punishment for delinquent or aggressive behavior seen in psychopaths. Research findings suggest that hormone systems work together in unison in the presentation of psychopathy, a concept that is a rather new development in the scientific field. Oddly, this study did not identify baseline testosterone and baseline cortisol level ratios as significant predictors for antisocial characteristics. Looking at the results, it is most evident as originally stated that the HPG and HPA axes are extremely influential.
What they suggest should be further examined for future research is the focus on these testosterone levels and how high or low they seem to be in relation with cortisol reactivity and the presentation of psychopathic traits. Previous research has stated that lower testosterone levels demote antisocial behavior while higher levels are seen to affect the amygdala in which people may exhibit impairments in withdrawal and the lack of fear that are characteristic of psychopathy. The results of this study support these high and low level testosterone differences. Their results did not correspond with studies that originally interested them, findings that include the idea that baseline levels of cortisol and testosterone are associated with psychopath. However, the study examined the hormone systems in its complexity and took new findings a step further. Results call for further development and research, especially because previous studies show more influences of cortisol and testosterone levels and the interaction implication is a newer concept.