A recent study in the American Journal of Psychiatry suggests that frontal lobe abnormalities of those with APD may contribute to violent behavior.

Naryan et al (2007) have completed the first study of the relationship between violence and brain structure in Antisocial Personality Disorder and schizophrenia, using magnetic resonance imaging (MRI) and found that violent individuals with APD do have significant anomalies in brain structure.

Violence and Frontal Lobe Abnormalities

Violent behavior has been linked to abnormalities in the frontal lobe, the area of the brain responsible for regulating inhibition, emotions, movement and overall social and cognitive behavior.

Studies dating back to the late 1800s have consistently found that damage to the frontal lobes results in an altered personality, particularly in increased impulsivity and impaired judgment (Damasio 1994).

Antisocial Personality Disorder (APD)

Common traits of APD include impulsivity, failure to conform to social norms, aggressiveness, disregard for safety, glibness, and deceitfulness. Not all violent criminals have Antisocial PD, but there those who do show a higher rate of severe violence than does the general population.

There have been few brain imaging studies of people with Antisocial PD. However, Raine et al (2000) found that individuals with APD have 11% less prefrontal gray matter than do healthy comparison subjects, suggestive that there may be significant anatomical anomalies with respect to the brains of antisocial individuals.

Study’s Method

Subjects

The subjects of this study included 14 men with a history of violence who had been diagnosed with Antisocial Personality Disorder according to DSM-IV-TR criteria, and 15 healthy nonviolent comparison subjects.

Both violent and nonviolent individuals who had been diagnosed with schizophrenia were also studied. For study results related to schizophrenia, see the original research paper, as these results will not be covered in this summary.

Neuroimaging

Each subject’s brain was examined with a series of high-resolution three-dimensional magnetic resonance images.

The Body’s Response to Risk

The organs of our body are regulated by a part of the nervous system called the autonomic nervous system (ANS). In most situations, we are unaware of the workings of the ANS because it functions in an involuntary, reflexive manner.

The ANS is most important in two situations:

1. Fear–inducing emergencies that cause us to "fight" or take "flight"
2. Nonemergencies when we "rest" and "digest."

Our body’s fear response sometimes prevents us from doing dangerous things or triggers us to engage in behaviors that will help up avoid perceived danger. It is a powerful motivator of behavior. The ANS response is normally associated with unpleasant physiological sensations such as sweaty hands, increased heart rate, tensing of muscles and dry mouth.

Psychopath’s Don’t Experience Fear

Violent APD individuals in this study exhibited substantial cortical thinning of the ventromesial frontal and sensorimotor cortex.

Somatic Cortical Loop

The involvement of the ventromesial frontal cortex has been associated with the body’s reaction to risky decision making, the somatic cortical loop. Involvement of mesial frontal and sensorimotor cortical thinning in APD may reflect disturbances in the somatic cortical loop. When parts of this circuit are dysfunctional, the appropriate behavioral responses may not be triggered and dangerous decisions or actions may be made (Fukui 2005, Damasio 1996, 1990).

Psychopaths' Reduced Autonomic Arousal

In his book on psychopathy, Robert Hare (1999) cites studies which have demonstrated psychopaths lack the physiological responses normally associated with fear. Psychopaths do not experience the physical clues that signal how to behave in dangerous or threatening situations. A study by Raine et al. (1990) found that a low level of autonomic arousal in adolescents was predictive of criminal behavior in adulthood.

Study's Conclusions

Taken together, these data suggest that because of a deficit in mesial prefrontal and somatosensory cortices, violent subjects have a compromised autonomic emotional response when making decisions and this insufficient autonomic response may be associated with violent decisions.

This Suite101.com article summarizes the results of a small study of the brain and antisocial behavior. It is not meant to be used for psychological diagnosis.

More Information on Antisocial PD

Additional resources on psychopathy and personality disorders in general include the Suite101 Antisocial Personality Article Series, the website Psychology Prof Online, and the article Personality Disorders: Brief Summary of the Ten Disorders of Personality.

Sources

Damasio A.(1996) The somatic marker hypothesis and the possible functions of the prefrontal cortex. Philos Trans R Soc Lond B Biol Sci, 351.

Damasio H. et al. (1994) The return of Phineas Gage: clues about the brain from the skull of a famous patient. Science, 264.

Damasio AR, Tranel D, and Damasio H. (1990) Individuals with sociopathic behavior caused by frontal damage fail to respond autonomically to social stimuli. Behav Brain Res, 41.

Fukui H. et al (2005) Functional activity related to risk anticipation during performance of the Iowa Gambling Task. Neuroimage, 24.

Narayan, V.M., Narr, K.L., Kamuri, V., Woods, R.P. et al. (2007) Regional Cortical Thinning in Subjects With Violent Antisocial Personality Disorder or Schizophrenia. The American Journal of Psychiatry, 164, 9.

Raine A. et al (2000) Reduced prefrontal gray matter volume and reduced autonomic activity in antisocial personality disorder. Arch Gen Psychiatry, 57.

Raine A., Venables P., Williams M. (1990) Autonomic orienting responses in 15-year-old male subjects and criminal behavior at age 24. Am J Psychiatry, 147.