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Why Are Men So Violent? --- What Science Says

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October 2, 2017

By SUSAN CALLAHAN, Associate Editor and Featured Columnist


All too regularly, when we wake up to the morning news, we are greeted with reports of attacks, mass attacks, terrorist attacks, lone gunman attacks, coordinated attacks, attacks in schools, on crowds at concerts, at cafes, in subways, at the metros, on airplanes, attacks, attacks, attacks. Almost every country on Earth has been touched by senseless violence.  Boom, boom, boom, all over the world but all of them have something in common and, no, it's not just religion. Numbed by it all, we never step back and ask the obvious: why, in close to 100% of these mass killings, are the perpetrators men?  Is the question itself taboo? Is the simple answer that men have more testosterone? We decided to take a look to see what science says about the connection between men and violence.

The FBI Did A Study of Mass Shootings

The FBI completed a study of mass killings in the US from the period 2000 to 2013. During this period, there were 160 incidents of  killings with active shooters, and 40% of these were "mass killings", meaning at least 3 people were killed.

The incidents with the worst body counts of course did not include the 58 people killed and 500 wounded in the attacks in Las Vegas on October 2, 2017 or the 49 people killed in Orlando. The worst killings in the 13 year period from 2000 to 2013 covered by the report included:


Analyzing these incidents, here is what the FBI researchers found:













All but 2 incidents involved a single shooter.

In at least 9 incidents, the shooter first shot and killed one or more family members in a residence before then moving to a more public location to continue shooting.

In at least 6 incidents, the shooters were female.This means that in 154 out of 160 such events, the shooters were male. That's 96.25% of the cases.

In 64 incidents (40.0%), the shooters committed suicide; 54 shooters did so at the scene of the crime.

When It Comes to Men, Is Suicide Risk Also a Public Threat Risk?

One striking statistic from this report is that 40% of the shooters also committed suicide. There is evidence that many of these shooters displayed fatalistic, end of life, thinking before they started shooting.

Many displayed violent thoughts on social media. After the shootings, the authorities combing their Facebook pages and other social media pages often found threats and violent thoughts expressed.

Sadly missing from many of these stories is the presence of mental health professionals.

Something Happened After 2007

Before 2007, there were mass killings. The average number of incidents were  6.4 active shooter incidents per year. In one year, 2000, there was a single incident.

But after 2007, mass killings have, well, exploded. The average numbers of such incidents from 2007 to 2013 was 16.4 per year, a jump of 2.56 times the average before 2006.

Bear in mind that mass killings are just a type of homicide.  The rate of total homicides in the US, since the mid 1990's actually has fallen 49%, according to the Pew Research Center.  But within that falling stat, the number of spectacular mass killings has steading increased.

What happened after 2007 to increase the number of mass killings in the US?  Again, no studies have pinpointed an exact cause.

But clearly, two things changed in 2007/2008. Once was the election of Barack Obama, our nation's first President of African descent. The other event was the Great Recession of 2008, which started just prior to President Obama's election.

Neither of these events has ever been proven to be causally related to mass shootings, however.

Yet, something clearly happened in 2007/2008 to triple the average number of mass killings and we need to try to find out what that is. Is it a mere coincidence? Did the Great Recession trigger a wave of depression that pushed those at the margins of mental stability into full-blown violent instability?


The Link Between Testosterone and Violence

To date, there is no study which has inventoried the testosterone levels of mass shooters. However, there is plenty of evidence linking testosteroe levels with violence in general.

A 2012 study from the University of Athens found that testosterone has two striking effects on the brain. It activates the amygdala, "enhancing its emotional activity and its resistance to prefrontal restraining control".

Thus, testosterone causes two effects which enable violence. It activates emotions and it makes it harder for the brain to restrain those emotions.

This study found that testosterone increases aggression while serotonin and cortisol act to block the effects of testosterone.

This makes some sense. Serotonin is a natural "feel good" hormone. If an individual is depressed, serotonin levels would be lower, thus there would be less serotonin available to block the effects of testosterone.

One famous 1972 study of testosterone and violence was led by Dr. Leo Kreuz of  The Johns Hopkins University School of Medicine. The study, which examined 89 prison inmates, found that 9 out of 11 of those who had committed the most violent acts also had the highest levels of testosterone. On the other end of the spectrum, 8 out of 11 of those who had the most non-violent records also had the lowest levels of testosterone.

It's unlikely that President Obama's election had anything to do with the increase in mass shootings. In fact, one study in 2008 from Duke University actually looked at the testosterone levels of voters before and after Obama's election. 

The study, called " Dominance, politics, and physiology: voters' testosterone changes on the night of the 2008 United States presidential election ", noted that political elections are dominance contests and such contests directly affect testosterone levels.

The study found that those who voted for the winner (Obama) saw their testosterone levels remain stable. This was significant because testosterone levels typically fall as evening unfolds, in line with the circadian cycle.

On the other hand, those who had voted for the loser (Mccain) experienced lowered testosterone levels as the election results rolled in.


Prescriptions of Testosterone Are Soaring

Testosterone doses are increasing at a fast clip in the US, UK and other countries. Since 2001, sales of testosterone doses to men over 40 have increased 300%. Now, 3% of all men in the US over 40 dose themselves with testosterone. In the UK, testosterone doses have doubled since 2001.

Testosterone naturally falls as men get older, thus lowering the risk of violence from older men. However, with the availability of testosterone dosing, we may begin to see that change. We may be entering an era when the levels of violence in our societies remain level, even as men age. It's an ominous sign that the shooter in Las Vegas who killed 58 people was himself aged 64.

Couple the increase of testosterone dosing with the ready availability of assault-style firearms and you have a prescription for danger and tragedy, over and over again.




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