The Anatomy of Violence (39 page)

Let’s move on to
Peru and the
Quolla Indians for another course in the recipe for violence. The Quolla have a very high rate of homicide and incessantly feud with each other, and have been called, a bit harshly, “perhaps the meanest and most unlikeable people on earth.”
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One anthropologist who studied them made the keen observation that a significant number of their acts of aggression seemed to be without good cause.
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He also noticed that the Quolla were often hungry and craved sugar. Could it be that their irrational aggression was due to low blood-sugar levels and reactive hypoglycemia? A
glucose-tolerance test, which assesses propensity for low blood-sugar levels, confirmed a relationship between low blood sugar and both physical and verbal aggression in the Quolla.
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When you next feel irritable and angry for reasons that are not obviously apparent, you might consider a quick
nutritious
nibble to restore your sugar levels—but not a Twinkie.

In
Finland,
Matti Virkkunen, who is a psychiatrist at Helsinki University, has been repeatedly demonstrating in some important studies very significant metabolic abnormalities in violent offenders that fit the low-blood-glucose idea. In a series of early studies, Matti demonstrated that violent offenders were more prone to hypoglycemia. He demonstrated that aggressive psychopaths had increased
insulin secretion, which would explain their low blood-sugar levels.
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More recently, Matti found low glucose metabolism and low levels of the hormone glucagon in another group of violent Finns.
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He then found that low glucose and glycogen formation predicted which violent offenders would go on to commit further violence eight years later, with the two measures explaining 27 percent of this future recidivism.
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If Matti Virkkunen and others are right, how exactly would the recipe of junk food, hypoglycemia, and low glucose metabolism push a person to violence and aggression? It goes something like this. Diets high in refined carbohydrates can cause extreme fluctuations in blood glucose levels—foods like white bread and white rice. Such foods have the bran, germ, and nutrients stripped from the whole grain, taking away the fiber. Because of the fiber loss, they are rapidly absorbed by the gut, resulting in a large and rapid increase of glucose swishing around in the bloodstream. This in turn triggers an inappropriately large secretion of insulin. Insulin’s job is to soak up the excess glucose and convert it into glycogen so that surplus energy can be stored for future use. But too much insulin release results in too much of the available glucose being taken out of circulation. This is bad news for the brain, which requires at least 80 milligrams of glucose a minute to function efficiently. Drop below that mark and you progressively observe symptoms of nervousness and irritability. That combo of increased irritability combined with feeling on edge could be the first step in the development of a full-blown
aggressive outburst. It’s not too surprising, therefore, that when glucose levels of subjects are experimentally lowered in the laboratory, people report feeling more angry even though there is no provocative stimulus.
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But what’s really shocking is a recent study by
Stephanie van Goozen and her colleagues at
Cardiff University in Wales that was conducted on a sample of 17,415 British babies born in 1970.
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When they were ten years old, the children were asked how often they ate sweets. Van Goozen showed that the kids who ate sweets
every
day were three times more likely to become violent by age thirty-four. They controlled for many factors, and the results remained significant.

If this relationship is causal, what’s going on? It could be reactive hypoglycemia. The kids who are helping themselves to candy at age ten are also helping themselves to a lifestyle of unhealthy eating habits—high-energy, highly refined carbohydrates that result in too much
sugar too quickly. The resulting rebound of very low blood sugar and symptoms of irritability can predispose a kid to giving someone else a good punch in the face in the school playground. Or, as an adult, a
broken bar glass in the face. Keep your kids off the candies.

If you think sweets are bad for you, they’re nothing compared with other things that can get inside you, mess up your
brain, and make you flex your muscles. I’ll suggest here that heavy metals can form some of the ingredients in the concoction for crime causation. Let’s take a look at a few of the key ingredients.

We saw in
chapters 3
and
5
that the structure and function of the brains of violent offenders—especially the prefrontal cortex—is compromised. We have also hypothesized that these brain impairments produce secondary effects—emotional, cognitive, and behavioral—which in turn shape
violence. Lead is a leading candidate as a source of these
structural and
functional brain impairments.

First and foremost, lead is
neurotoxic, meaning that it kills
neurons and damages the
central nervous system. The neurotoxic effects of lead have been known for millennia, and efforts to reduce it are not recent. They have a connection to my favorite drink in England—
cider. Back
in the seventeenth and eighteenth centuries there was a common malady known as
Devon colic, a neurological condition that particularly afflicted people in the southwest of England. They grow a lot of apples down in Devon and cider was almost a staple drink there back then. It was thought that the acidic apple juice caused the colic. Yet in the late eighteenth century
George Baker, a physician, identified the cause as lead contained in the cider presses. Over the next few decades lead was steadily taken out of the presses. A near-miraculous reduction in Devon colic occurred, proving Baker’s hypothesis.

Lead’s
neurotoxic effects are documented in brain-imaging studies of workers exposed to the metal in their jobs. One study scanned the brains of 532 adult men who had worked in a lead chemical plant.
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There was a wide range of bone-lead levels in these participants, but an average reading was at the very top of the safety level.
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Workers with relatively high bone-lead levels had smaller
volumes of many brain areas even after controlling for multiple confounds like age and education levels. The fact that the
frontal cortex was particularly reduced
⁶⁵
is very interesting, given that this brain region is involved in violence. This lead effect was equivalent to five years of
premature aging of the brain.

So lead workers have brain volume reductions. What about people in the community like you and me who likely have just low to moderate levels of lead in our blood? This question was addressed in a study of 157 individuals from Cincinnati who had had their blood-lead levels measured twenty-three times from the ages of six months to six and a half years.
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This prospective study again showed that those with high lead levels had low brain volumes. One of the brain regions most affected was the ventrolateral prefrontal cortex, that lower outer region of the front of the brain that is impaired in antisocial and
psychopathic individuals. This community sample had an average blood-lead level at age six that was high, but still within the so-called “safe” range as defined by the
Centers for Disease Control and Prevention. We can see, then, that those exposed to “safe” levels of lead can suffer from brain impairments. Furthermore, the prospective nature of the study, moving from childhood lead
exposure before age six to brain structure at age twenty-three, helps to establish causality.
⁶⁷

These studies give clear documentation of the negative impact of lead on the brain, and, intriguingly, they also document that the brain area most frequently found to be compromised in violent populations—
the frontal cortex—is particularly impacted by
lead exposure. The next question is whether those with high lead levels are found to be more antisocial.

The landmark study in this area was conducted by
Herbert Needleman at the University of Pittsburgh. He found that boys with high lead levels have higher teacher ratings of delinquent and aggressive behavior, and also higher self-reported
delinquency scores. It was an impressive and influential study. Similar links have been found in at least six other studies in several different countries.
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Furthermore, experimental exposure to lead during development increases aggressive behavior in hamsters, thus suggesting a causal link.
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Environmental lead exposure, therefore, is a risk factor for antisocial and aggressive behavior in delinquent kids. What about adult crime? And how early in life does this association occur? Answers to these questions were obtained in a methodologically strong study of
African-American pregnant women.
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Both prenatal and postnatal blood-lead levels in their offspring dramatically predicted adult crime in the early twenties and also adult violence. For every 5 microgram increase in prenatal blood-lead levels, there was a 40 percent increase in the risk for arrest.
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Given that a 5 microgram increase from birth to age five still keeps you well below the limits of what the
Centers for Disease Control and Prevention considers safe, this constitutes substantial risk from just a moderate, “safe” amount of lead exposure.

The last study shows that blood lead very early in life is an important predictor of adult crime. We also know that blood-lead levels are maximal at twenty-one months, when children are most exposed to lead.
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Why is that? You know that toddlers put their fingers in their mouths a lot. And they also get their fingers into every pie they can, including mud pie outside in the garden. Lead lingers well after its release into the environment and stays in the soil for years. Even though gas is now unleaded, the lead residue from the past still lingers in the soil, especially near major roads and freeways.

High blood-lead levels later in childhood can be even more important. One study in Yugoslavia
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recruited pregnant mothers in 1992, just at the time of the large-scale ethnic conflict between the Serbs and the Croats. The mothers came from two towns near lead smelters. Blood-lead levels in their offspring at age three were more strongly related to destructive behavior than the prenatal measures of blood lead. Similar findings have been obtained in America, with high blood lead at age
seven—but not age two—correlating with high antisocial and aggressive behavior at age seven.
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So
lead exposure still matters well after the age of twenty-one months.

Lead research lends itself to an intriguing conceptual point. What has puzzled criminologists is the unpredicted drop since 1993 in violence after a continuous rise, which flew in the face of criminological predictions of further increases. For example, within seven years violent
crime in
New York had dropped 75 percent. Many sociopolitical explanations were given, but none could account for both the rise and the fall in crime across several decades. Critics of neurocriminology argue that biology cannot, of course, explain differences in violence over time or across regions within a country. Isn’t biology fixed and static? Surely it cannot explain secular trends—shifts in violent crime rates across time.

But it can, and dramatically so. In research papers buried in an obscure environmental journal,
Rick Nevin documented a strikingly strong relationship between changes in environmental lead levels from 1941 to 1986, and corresponding changes in violent crime twenty-three years later in the United States.
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So, young children who are most vulnerable to lead absorption go on twenty-three years later to perpetrate adult violence. As lead levels rose throughout the 1950s, 1960s, and 1970s, so too did violence correspondingly rise in the 1970s, 1980s and 1990s. When lead levels fell in the late 1970s and early 1980s, so too did violence fall in the 1990s and the first decade of the twenty-first century. Changes in lead levels explained a full 91 percent of the variance in violent offending—an extremely strong relationship.

Nevin found exactly the same matching of the lead levels and violence curves in Britain,
Canada, France,
Australia,
Finland, Italy, West
Germany, and
New Zealand.
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There was cross-cultural replication. Furthermore, in states where lead levels dropped more quickly, later violent crime also dropped more quickly.
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Variations in lead levels even correlate with variations in crime rates within cities.
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From international to national to state to city levels, the lead levels and violence curves match up almost exactly.

Kevin Drum, a political blogger and columnist argues that these findings have been completely ignored by criminologists. He contacted criminology experts and none of them showed a scrap of interest.
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Why? Likely because to recognize that secular trends and both rises and falls in violence can be partly attributed to brain dysfunction—and not to
better policing or to gun control or to the end of the crack epidemic —would be to recognize the explanatory power of biology theories. Currently that’s something very difficult for many social scientists to accept.

At a
McDonald’s next to the post office in the community of San Ysidro, near San Diego, at 3:40 p.m., on July 18, 1984, a middle-aged man walked in with a 9-millimeter
semiautomatic Uzi and unloaded 257 rounds of ammunition into the customers. The shooter,
James Oliver Huberty, killed twenty-one people and wounded nineteen others.
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His victims ran the gamut in age from just seven months to seventy-four years.

What on earth made Huberty do it? Cadmium is a very likely culprit. An analysis was made of Hubert’s hair after he was shot dead by a SWAT team sniper perched on the roof of the next-door post office. The results were nothing short of astonishing. In the words of William Walsh, the chemical engineer conducting the analysis, “He had the highest cadmium level we have ever seen in a human being.”
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Huberty’s lead levels were also high, so he had a double hit. There’s no mystery as to why he had multiple metals in his body. Huberty had been a welder for Union Metal for a number of years until he gave it up. The reason he left his welding position? In an exit interview that he gave to his employer upon leaving, he said, “The fumes are making me crazy.”
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