Violent Tendencies: Are Brain Injuries to Blame?
It’s a common belief that people with a brain dysfunction or abnormality behave violently. This assumption is supported somewhat by insights from neuroscientific studies, which reveal that those who commit criminal acts often have marked brain differences compared to individuals who do not engage in criminal behavior. These brain differences—which are observed using a magnetic resonance imaging (MRI) scan—include in antisocial individuals as well as perpetrators. But how strong are correlations, and is there also a causal relation? Engaging in criminal acts could be associated with a variety of factors such as genetics, parental influences, early life experiences, and hormones, . However, these contextual factors are overlooked, as brain abnormalities—which may come from brain injuries or impromptu tumors—bear the brunt of blame. that many offenders who exhibit antisocial and/or violent behavior have in brain structure compared to “healthy normal subjects.” Behaviors that are antisocial and/or violent tend to be predictive of criminal behavior as they violate the rights of others, which sometimes amounts to criminal behavior. These differences in the antisocial/violent brain compared to the “normal” brain are predominantly observed in the prefrontal cortex, as examined in a . The sample of the meta-analysis included 43 structural and functional brain imaging studies. The studies were selected on the basis of three criteria; if they included at least one antisocial group (individuals with antisocial personality disorder, conduct disorder, psychopaths, criminals, violent offenders, or aggressive individuals) compared to a control group of “healthy normal” subjects, at least one certain type of imaging method (fMRI, MRS, PET), and if the imaging method included assessment of either the structure or function of the prefrontal cortex.
The prefrontal cortex has long been recognized as “the most crucial (although not the only) brain structure to be compromised in violent and antisocial populations,” according to the researchers from the 2009 meta-analysis. It is mainly responsible for “attention, planning, working memory, and the expression of emotions and appropriate social behaviors,” according to the . The meta-analysis found that antisocial individuals had reduced prefrontal structure and function. Since criminal behavior is associated with deficits in many of the prefrontal cortex’s roles—such as failure to exhibit behavior that is socially appropriate— damage to this region can correlate with antisocial, violent, and eventually criminal behavior.
This study, like many others, has found marked differences in how the brain of criminals looks and operates. These marked brain differences are more pronounced after a brain injury. Seemingly normal individuals without any observed history of antisocial or violent behavior may develop these behaviors after sustaining a head injury or after developing a tumor (excluding factors such as genetics, family influences, etc.). In a , researchers found that a tumor in the orbitofrontal region preceded pedophilia in an individual. The individual was unable to inhibit sexual urges, but once the tumor was removed, his behavior returned to normal. In a involving war veterans, higher levels of aggression were found in veterans who experienced injuries to the —a region in the prefrontal cortex that represents reward and value-based decision-making, generates and regulates negative emotion, and influences social cognition. In a , researchers found that among individuals with —a brain disorder that involves abnormal neuronal activity—4.2% committed a violent crime after diagnosis. When compared with the 224,006 subjects in the control group, individuals with epilepsy had significantly increased odds of committing a violent crime, Among the individuals with a traumatic brain injury (TBI), 8.8% committed a violent crime after diagnosis, which also was significant when compared to population controls. The initial results from this study indicate a strong correlation between brain abnormalities and/or injuries and criminal behavior.
Many factors contribute to the development of criminal behavior, and it is unfair to overlook contextual factors. One sole piece of evidence cannot be determined as the cause of crime, neither can it excuse it. The integration of multiple factors can help to explain criminal behavior and potentially determine a cause that is multi-faceted. In the 1996 study on war veterans, the presence of aggressive and violent behaviors was associated with a disruption of family activities in addition to observed brain associations. This expands the correlation between brain injuries and behavior to other contextual factors. It also diversifies the reasons why participants’ aggressive and violent behaviors emerged. In the 2003 study on the pedophilic individual, there may have been other factors that contributed to his behavior. Perhaps he had a genetic susceptibility to pedophilia that was not accounted for, or he had childhood experiences that shaped his behavior. In the longitudinal study, when the results were examined further, the researchers found that their original results—which predicted that those with a TBI or epilepsy had higher odds of committing a violent crime—were less significant once these affected individuals were compared to their unaffected siblings. The percentage of violent crime committed by those with TBI/epilepsy was nearly the same as the percentage of violent crime committed by their unaffected (not having TBI/epilepsy) siblings. This suggests that genetic and environmental factors—which the affected individuals shared with their siblings and not the population controls—have a greater role in influencing violent behavior than the brain abnormalities associated with these conditions. Additionally, in the longitudinal study, researchers found “heterogeneity in violence risk by age of disease onset, severity, comorbidity with substance abuse, and clinical subgroups”, further expanding implications for criminal behavior.
When we encounter people who are known to have sustained brain injuries there are many things to consider before falling back onto the stigma that these people are antisocial, violent, and criminally motivated. Most likely, people with brain injuries—or who have had them in the past—suffer from a detriment in a specific area of the brain. If it was in the —a part of the brain responsible for speech production—for example, this individual may not be as prone to criminal behavior as someone who has suffered an injury to the prefrontal cortex, as the prefrontal cortex regulates brain processes that normally inhibit criminal-like cognitions and executions. Additionally, brain injuries are not the sole reason for one’s behavior, there are other factors at play that can help to explain why someone is acting a certain way. Perhaps one’s childhood experiences with an antisocial or violent family are influencing one’s behavior; or one’s genetic predisposition to antisocial tendencies is becoming more pronounced in addition to this brain injury. Thus, one must not equate brain injury with violent tendencies but also must consider other contributing factors.
These considerations for interacting with people who have brain injuries can be implemented in a wide range of contexts. Maybe you can change the way you interact with friends or family members with a brain injury. Your attitudes towards veterans——and those involved in the legal system that have an identified brain injury may also become more understanding. Maybe, as a mental health or legal professional, you change the way you place blame on an individual and expand your judgements of pathology. We must recognize what individuals with brain injuries involved in criminal behavior can control, and while some aspects of their behaviors are hard to inhibit, the moral responsibility for their actions must be weighed. Brain correlations are not the be-all-end-all “causes” of crime. An in-depth, all-encompassing approach to criminal behavior pathology provides for a better understanding and treatment of these affected individuals. This can further reduce stigma associated with criminally involved individuals and prompt well-informed policy change—such as screening for brain injuries in the criminal justice system or supporting programs with rehabilitation efforts towards those with brain injuries.