The Neuroscience of Violence, Again

The first dead person I ever saw was a policeman. . .

He was lying face down on the asphalt at the center of a crimson puddle the size of my wading pool.  I was too young to understand.  Too young to even identify the red stuff, until my mom told me.  It was too thick and gelatinous and there was too much of it to be blood.  He had been shot and killed in a robbery just before we got to the store entrance.  He died trying to stop a crime, putting himself between a killer and innocent people he did not know.

Last week I met a woman who had graduated from Columbine High School in Colorado.  A teacher close to her was one of the many people who died.  He bled to death before the police could get to him.  A few years later, another one of her friends was shot four times at Virginia Tech while studying in his French class.  He was one of 17 who survived.  32 others were murdered.

This week an acquaintance of mine will be sentenced for murdering his mentor of 20 years.  He clubbed him to death with a hammer in a vicious fit of rage.  I also knew the man he killed.  I describe this tragedy in my book, Why We Snap, to illustrate the inconceivable rage attacks that happen every day between friends, but to maintain the presumption of innocence until the trial, much was edited out of that chapter.  The sad story does illustrate that no one snaps violently except in response to a few specific types of provocations playing against a background of chronic internal or external stresses.  The underlying stresses rarely make the newspapers, which leaves us baffled by the violence.  They say the Dallas shooter snapped,1 but what does that mean?  The physiology of stress and the neurocircuits of rage and aggression are brain functions that can be studied and understood.

From Orlando to Baton Rouge to Falcon Heights Minnesota to Dallas, it has been a difficult and disturbing period.   In view of this, my editor at asked to rerun an earlier article I wrote on the neuroscience of violence.  The reasons are twofold:

First, to face the fact that throughout the prime of life, violence, whether in suicide or in homicide, is a leading cause of death for Americans.

Second, is that while we will hear endless political, social, and psychological analysis of these recent violent tragedies, there will be little discussion from the perspective of biological science.  Violence, like all behaviors, is controlled by the brain.  New research in neuroscience is identifying the brain circuits of rage and aggression in ways that have not been possible before.

Research to understand and cure disease is widely appreciated, but there is a larger unmet need to understand the neuroscience of violence.  For example, many unjustified police shootings are the result of the brain’s threat detection and response mechanism acting aggressively in a sudden moment of extreme danger.  While a criminal will not hesitate to shoot first and ask questions later, a police officer cannot, so the brain’s response to acute stress, danger, and fear must be fully understood so that it can be controlled and exploited.  As another example, brain imaging and EEG recordings are revealing how the prefrontal cortex instantly and unconsciously classifies anyone we see as a member of your own group, or a potentially dangerous person outside our own group.

It is natural to dismiss horrendous violent acts as the result of mental illness, but epidemiological research published in 2016 shows that serious mental illness contributes little to the risk of interpersonal violence.2  Mental illness is a strong factor in suicide however.  The same study found that most firearm fatalities are suicides, not homicides.  The statistics show that most firearms used in gun crime and one third of the guns used in suicide are obtained illegally, putting these deaths beyond control of gun laws.  Another study published in April, 2016 in the journalLancet finds that of 25 new firearm laws implemented in different states in 2009, seven had no effect on deadly gun violence, nine increased firearm deaths, and nine reduced deaths from firearms.3  The most effective laws in reducing gun deaths were universal background checks for firearm purchase, ammunition background checks, and identification requirement for firearms.

The inescapable fact is that violent death is an extraordinarily serious problem in the United States, compared with other high-income countries.4  Homicide rates in the US are 7 times higher than other high-income countries.  The homicide rate from guns in the US is 25.2 times higher.  For young people between the ages of 15-24, gun homicide rates in the US are 49 times higher.

To read about new research on the neuroscience of violence, see:



1. Zapotosky, M., Goldman, A. and Higham, S. (2016)  Portrait of sniper raises more questions than answers.  The Washington Post, July 9, 2016, p. A4.

2. Swanson, J.V.V. et al., (2016) Gun violence, mental illness, and laws that prohibit gun possession:  evidence from two Florida counties.  Health Aff. 35: 1067-75.

3. Kalesan, B., et al., Firearm legislation and firearm mortality in the USA: a cross-sectional, state-level study.  Lancet 387: 1847-55.

4. Grinshteyn, E. and Hemenway, D., (2016) Violent death rates:  The US compared with other high-income OECD countries, 2010.  Am. J. Med. 129: 266-73.


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