Given an impending return to an official diagnosis of psychopathy in the DSM-V and the advances and developments in neuroimaging over the past decades, the role of neuroimaging in the diagnosis, treatment and understanding of psychopathy is of ever increasing interest. This paper describes and combines data and discussion from recent journal articles, reviews, and text books regarding neuroimaging and psychopathy as well as touches on some of the ethical and legal implications of this work. Recent findings indicate that a return to a clinical diagnosis of psychopathy in the DSM-V is indeed warranted and that there is emerging evidence of distinct subgroups of psychopaths that may be characterized both by overt behaviors and neuroanatomical anomalies. However, given the nature of the population and the research, it is very difficult and even unwise to begin, at this point, drawing solid cause and effect relationships between specific neuroanatomic features and any overt deviant behavior.
Although, at the moment, psychopathy is not an official diagnosis contained in either the Diagnostic and Statistical Manual IV – Text Revision (DSM-IV-TR) or the International Classification of Disease 10 (ICD 10) the use of psychopathy as a descriptor has been growing increasingly popular both within scientific research and clinical practice (Müller, 2010). The importance of the concept of psychopathy is further evidenced by the discussion of and apparent decision to return to an official diagnosis of psychopathy in the upcoming DSM-V. The DSM-V workgroup is recommending that antisocial personality disorder henceforth be revised as Antisocial/Psychopathic Type (DSM-V, 2011). This appears to be part of a broader effort to consolidate and refine personality types as a whole with the old ten being reduced and simplified to 5: Antisocial/Psychopathic, Avoidant, Borderline, Obsessive-Compulsive, and Schizotypal types (DeFife, 2010).
Psychopathy can begin to be “defined by a pattern of interpersonal, affective, and behavioral characteristics, including egocentricity, deception, manipulation, irresponsibility, impulsivity, stimulation-seeking, poor behavioral controls, shallow affect, lack of empathy, guilt, or remorse, and a range of unethical and antisocial behaviors, not necessarily criminal.” (Müller, 2010). Psychopathy can be further defined and described by the revised psychopathy check list (PCL) (Tunstall, Fahy, & McGuire, 2003).
Revised psychopathy checklist (PCL)
(1) Glibness/superficial charm
(2) Grandiose sense of self-worth
(3) Need for stimulation/proneness to boredom
(4) Pathological lying
(6) Lack of remorse or guilt
(7) Shallow affect
(8) Callous/lack of empathy
(9) Parasitic lifestyle
(10) Poor behavioural controls
(11) Promiscuous sexual behaviour
(12) Early behavioural problems
(13) Lack of realistic, long-term goals
(16) Failure to accept responsibility for actions
(17) Many short-term marital relationships
(18) Juvenile delinquency
(19) Revocation of conditional release
(20) Criminal versatility
(Tunstall, Fahy, & McGuire, 2003)
Interestingly, “The cut-off point for a case-level diagnosis of psychopathy is 30 in
North America and 25 in the UK” (Tunstall, Fahy, & McGuire, 2003).
Some issues surrounding the recent neuroanatomical imaging studies appear to revolve around a difficulty in access to a true homogeneous group of so called psychopaths. This in part lies with issues of comorbidity, along with an already limited population size. “Conditions which
might be considered comorbid with psychopathy are schizophrenia, anxiety and mood disorders, substance abuse disorders, and [attention deficit disorder] ADHD” (Blair, Mitchell, & Blair, 2005). In part due to these difficulties, but also as a result of recent imaging work, we are beginning to see the general concept of psychopathy be broken down into various subtypes. Wahlund
& Kristiansson (2009) suggest an altogether abandonment of the concept of
psychopaths as a homogeneous group. Instead,
they suggest that in the future, researchers and clinicians may benefit from a
finer distinction between subtypes of psychopath. Specifically a distinction between “primary,
more calculated and controlled psychopaths who often use predatory violence,
and secondary, more impulsive psychopaths who often commit affective violence.” .
Another group of researchers attempt to distinguish between distinctly
different subtypes. In their 2010 paper,
Yang, Raine, Colletti, Toga, & Narr explore and convincingly provide
evidence that the idea of a “successful” and “unsuccessful” psychopath may be
important for future research. Their work demonstrates “that the morphology of
prefrontal and amygdala structures differs between the two psychopathic
subgroups investigated, namely unsuccessful and successful psychopaths.”
Further, there exists “prominent structural deficits in the [middle frontal
cortex] MFC, [orbitofrontal cortex] OFC, and the amygdala in unsuccessful
psychopaths but not successful psychopaths, suggesting that these impairments
may predispose unsuccessful psychopaths to increased risky behavior and account
for their inability to process social and emotional cues to avoid criminal
As evidenced by Yang et al.’s work there exists a growing and substantial body of work evidencing a number of structural differences in psychopaths when compared to controls and even between various proposed subtypes of psychopath. The primary brain regions implicated in psychopathy are the Prefrontal Cortex, Temporal Cortex, Amygdala and Hippocampus, Corpus Callosum, and the Angular Gyrus
. (Raine, & Yang, 2006).
Prefrontal cortex: There has been a great focus on the prefrontal cortex within the literature. This is likely, in part, because as far back as “the famous case of Phineas P. Gage, lesion studies [have] linked prefrontal, in particular ventromedial and orbitofrontal, cortical damage to impairment in social behavior and decision-making” (Müller, 2010). This includes longitudinal studies of children who suffer lesions early in life as described by Raine & Yang (2006). These studies following children provide pseudo-experimental evidence “that head (and therefore brain) trauma can directly lead to antisocial and aggressive behavior” Further, the prefrontal cortex can be described as “part of a neural circuit that plays a central role in the acquisition of moral emotions such as embarrassment, guilt and remorse” (Verplaetse, 2009). This history of data on the prefrontal cortex indicates that we should expect to see structural differences in this region in comparisons between psychopaths and so called “normals;” that is exactly what we find. Earlier studies found a significant reduction of prefrontal grey matter in individuals with antisocial personality disorder when compared to control groups. Later studies, as mentioned earlier looking at more specific subgroups (successful and unsuccessful) of psychopaths found a staggering a 22.3% prefrontal gray matter reduction in unsuccessful psychopaths when compared to controls while identifying no significant difference between so called successful psychopaths and controls
. (Müller, 2010). PET and SPECT scans also identify reduced
metabolic activity in the prefrontal cortex as well as other regions in
“individuals with a life history of aggression, violence, and murder” (Husted, Myers, & Lui, 2008). As
mentioned earlier, alcoholism has a high comorbidity with psychopathy but it
appears that this alone can not account for the structural
differences identified in imaging studies at least of individuals with
antisocial personality disorder. Research
has found reduction in prefrontal brain matter in individuals with antisocial
personality disorder even when compared to populations of alcohol and drug
dependent individuals . (Raine, & Yang, 2006).
Temporal Cortex: Increases in activity within the temporal lobe have been associated with classical conditioning and implicated in the processing and remembering of emotional words (Pridmore, Chambers, & McArthur, 2005). The left anterior middle temporal gyrus has been implicated in empathetic judgments (Tunstall, Fahy, & McGuire, 2003). Again, as this is something psychopaths are characteristically deficient in we would expect to find anatomical differences in this region when comparing psychopaths and normal controls. Again this is exactly what is found in the neuroimaging studies. In describing research looking at individuals with antisocial personality disorder, Pridmore, Chambers, and McArthur (2005) note that this group showed significantly lower metabolic activity in the temporal cortex when compared to controls. Müller (2010) describes research looking at incarcerated impulsive-aggressive personality-disordered individuals that found a “20% volume reduction of the temporal cortex”.
Amygdala: The amygdala has also been shown to play a role in empathetic processing (Wahlund, & Kristiansson, 2009) as well as the processing of negative affect (Pridmore, Chambers, & McArthur, 2005). Yet again we find evidence of anatomical differences in these regions within psychopathic populations. Particularly, as descriptions of Yang and Raines’ research touched on, within the specific sup group of unsuccessful psychopaths (Yang, Raine, Colletti, Toga, & Narr, 2010). They identify volumetric reductions in the amygdala within this population.
Hippocampus: The hippocampus is involved in classical conditioning and social learning. A strong negative correlation has been identified “between the psychopathy scores and the volume of the posterior half of the hippocampus on both sides of the brain” (Pridmore, Chambers, & McArthur, 2005). The researchers assert their findings should not be generalized beyond alcoholic and violent psychopaths however other research previously described indicate this might not be too large of an issue, although further study is certainly needed and warranted. Also, the merits of looking at specifically violent offenders may be supported by previously described research examining the distinction between successful and unsuccessful psychopaths. Yang and Raine (2006), in the Handbook of Psychopathy discuss findings of increased activity in the hippocampus in both impulsive and planner murders when compared to controls.
, and the Angular Gyrus: In research
looking at the corpus callosum with a MRI, evidence was collected indicating a 23%
increase in callosal white matter volume, which corresponded with a significant
increase in interhemispheric functioning. Some functional imaging
studies have slightly reduced metabolic processes in both the corpus callosum
and angular gyrus in murderers .
(Pridmore, Chambers, & McArthur, 2005).
It is important to note that imaging technologies, while improving rapidly in both temporal and spatial resolution, are still in relatively early stages of technological development and application. Further, it must be noted that at best, ethically, we can only perform pseudo-experimental studies looking at the long term effects of childhood lesions that are generated via non experimental means and in uncontrolled manners. Everything else is purely correlational. This leaves much to speculation in regards to causal links between any particular structural abnormality and necessarily evoke a ‘chicken or the egg’ type problem. Glenn & Raine eloquently discuss this issue stating “an abnormality in a particular brain region does not imply that the abnormality was the cause of a specific behavior or crime. Rather, it should be taken into consideration as one of many factors, biological or social, that may increase an individual's risk for criminal behavior”
(Glenn, & Raine, 2009). This
point is reiterated by Raine, & Yang in The
Handbook of Psychopathy. The authors state that while anatomical
deficiencies appear to be reliably found within paychopathic individuals and in
varying degrees across psychopathic populations, imaging studies alone do not
demonstrate a causal link between the
observed structural anomalies and psychopathy or criminal behavior. They go on to explain that “in all likelihood,
brain deficits in psychopaths are likely to be caused by a combination of both
early environmental health factors and genetic processes” (Raine, &
Yang, 2006). Glenn and Raine again touch
on this issue, while at the same time slightly expanding upon it, by noting
that beyond currently being unable to draw causal links between the observed
structural deficits and psychopathy, “the source of most of the neurobiological
abnormalities discussed above is unknown, and may result from genetic,
developmental, or environmental factors.” (Glenn, & Raine, 2009).
All of this research coalesces into an interesting picture of psychopathy and criminal behavior that raises a broad scope of ethical and philosophical implications for treatment as well as within the realm of criminal justice. On the bright side, if psychopathy does in fact turn out to be caused by the observed brain deficits, then it stands to reason that psychopathy may be remediated via some type of intervention, possibly even at various stages of development, including preventative measures. These interventions may include neurosurgical, neuropharmacological, and possibly cognitive behavioral therapies
(Raine, & Yang, 2006) (Glenn, & Raine, 2009),
Raine, likely due to his large contributions to this field, seems to have made it a point to comment on the ethics of the application of this technology. In the 2009 article “Psychopathy and instrumental aggression: evolutionary, neurobiological, and legal perspectives,” authored by Glenn and Raine, the authors take the time to highlight that while it may soon be possible to apply these developing technologies and sciences to identify individuals who are more likely to engage in future criminal behavior, there are many dangers in actually applying these technologies to this end. They specifically mention the possible “harm caused by labeling, miscategorization, and the potential misuse of such information to limit the freedoms of some individuals.” This concern has led rise to a new discipline which has been termed “neuroethics.”
T.B. Benning in a correspondence with the British Journal of Psychiatry (Benning, 2003) discussed one possible, and many would argue undesirable, application of the research described above within a historical context. Benning draws parallels between current efforts to draw strong causal links between anatomical structure and antisocial as well as criminal behavior and the efforts of Cesare Lombroso, an Italian psychiatrist and criminologist in the late 19th century. “Lombroso believed that 40% of criminals were ‘born criminals’ who could be distinguished by physical features including relatively long arms, prehensile feet with mobile big toes, low and narrow forehead, large ears, thick skull, large jaw, etc.” (Benning, 2003). Benning quotes Lombroso as saying ‘society need not wait for the act itself, for physical and social stigmata to define the potential criminal. He can be identified, watched and whisked away at the first manifestation of his irrevocable nature.’ This is a particularly disturbing proposal given the erroneous nature of his link between the listed physical features and criminal behavior. Benning reminds us of Lombroso as a caution that our application of findings within this relatively new arena must not outpace our actual understanding of the underlying principals, lest we be looked upon by future generations of students, researchers, and practitioners with the same shocked amazement we feel when reflecting on the hypothesis of Lombroso so many years ago.
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