The Big Story

Can your genes make you kill?

Can your genes make you kill?

Posting in Science | From Issue 17 May 5 & 12, 2014

Was Adam Lanza a natural-born killer? Scientists are mapping his DNA to find out, but a debate swirls around what should be done with the results.

Just days after Adam Lanza slaughtered 20 children and six staff members at Sandy Hook Elementary School in Newtown, Connecticut, in December 2012, the state medical examiner delivered a chunk of his brain to scientists. The forensic chief asked them to undertake a novel task: sequence the 20-year-old killer’s DNA in hopes of finding abnormalities that could answer an almost unanswerable question: why?

No one has ever sequenced a mass murderer’s genes. And the plan to do so, by University of Connecticut geneticists, is being conducted quietly and far from the media spotlight. The University won't comment on its research, other than to admit that they indeed undertook it. It's not clear whether they have concluded their research, but the scientists most likely looked for mutations linked to mental illnesses, such as schizophrenia, autism or Asperger’s—a diagnosis psychiatrists had given Lanza years before his rampage. Neither the researchers nor the medical examiner’s office have said what they plan to do with their findings.

But the research itself, which made news at home and around the globe when it was first revealed a few weeks after the shootings, has set off a scientific and ethical debate. The argument, among fellow geneticists, criminologists and psychiatrists, goes something like this: Can we find a genetic cause to violence? Is it right to even look for such aggression triggers in genes? And what should (or might) be done with the findings?

Plenty of experts agree that vile acts like Adam Lanza’s involve a complex mix of various genetic and environmental factors. And searching for causal links to his crime could stigmatize people who share the same genetic markers. It may also be fruitless.

“Let’s say everything worked and we now have a genetic marker to say, ‘Oh look, this one gene makes someone a killer,’” says Heidi Tissenbaum, a geneticist at the University of Massachusetts medical school. “Will a person really become a killer? Do all women with breast cancer gene get breast cancer? No. So what are we doing?” 

When scientists sequence DNA, they are determining the precise order of its four base nucleotides—adonine, guanine, cytosine, and thymine—within a single strand. Sequencing isn’t really all that hard these days, thanks to the human genome project, which mapped all the genes in the human genome, and thanks to advances in mass spectrometry and other diagnostic tools.

In a recent New Yorker profile, Peter Lanza, Adam’s father, noted that Asperger’s makes people unusual, but not violent, and said that it might have instead “masked” an illness that is often associated with sudden and explosive violence: schizophrenia. His interviewer, Andrew Solomon, went on to note that when autistic people turn violent they are often reacting to “an invasion of personal space,” which was not what triggered Lanza's rampage. He added that an intensity of their preoccupations, particularly those with a “sinister aspect,” could provide a warning sign for violence. And Lanza had in fact become obsessed with researching mass murder over the internet in the months leading up to his attack.

The Connecticut scientists, who declined requests for interviews, might also look for specific genes linked to an increased risk to violence. Or they may map his entire genome, searching for deletions, duplications and mutations. The problem in such a search, says Tissenbaum, is the very limited quantity of subjects. Most major gene studies involve thousands of people over decades of research. Consider the Framingham Heart Study—begun in 1948 with 5,209 adults, and now in its third generation of participants—which is providing a wealth of information for geneticists looking within it to identify inheritance patterns and genetic correlations for cardiac disease. “Even if we have the brains of 40 mass murders,” says Tissenbaum, “think of how many variables there are in their age, ethnicity, their upbringing, their environment, diets, exposure to things in the womb, all the things that can affect DNA. Finding cause and effect is impossible.”

That hasn’t stopped plenty of well meaning—and some not so well meaning—people from trying. Science has a long and complex history of looking for genetic causes to violence and crime, nearly all of it fraught with ethical failure. The early 20th-century eugenics movement saw the sterilization of criminals—believed to have inherited their proclivities—to prevent future felons. The movement died out in the United States with World War II, but quietly re-emerged, in scientific guise, in 1965. That year, researchers suggested that men born with an extra Y chromosome (the chromosome that makes men male after all) were in fact “super males”—and thus innate criminals. Some of the subjects of the studies, nearly all of them institutionalized, were deemed “mentally sub-normal male patients with dangerous, violent or criminal propensities.” The hypothesis eventually fell out of favor after countless researchers determined that plenty of men without an extra Y chromosome turned out to be just as violent or vile.

Less than a generation later, sophisticated DNA analysis opened a window on to the biological triggers for disease, and scientists sought to explain human behavior as a consequence of gene mutation. In what was then hailed as a landmark 1993 study, researchers traced the lack of a single DNA enzyme, monoamine oxidase A (MOAO) to a 1960s Dutch family of rapists, rageaholics, arsonists, and, oddly, exhibitionists. Monoamine oxidase A breaks down neurotransmitters in the brain, such as serotonin and dopamine, once they’ve done their job. But an MOAO deficiency leads to a build up of these neurotransmitters, which in turn, say scientists, leads to higher levels of aggression. The scientific press and the mass media dubbed it the “warrior gene.” But subsequent research into what scientists call genomic “hotspots,” where deletions or copies have been found and linked to aggressive behavior, have been inconclusive.

Nevertheless, given the casualty counts racked up by crazed gunmen—in places like Newtown, at Columbine High School, at Virginia Tech, in the Aurora, Colorado movie theater, at the Norway summer camp—geneticists like Dr. Arthur Beaudet think the search for genetic links will be important to one day saving countless lives.

“I think there is a role for science to play and I think it absolutely has to be done,” says Beaudet, a professor at the Baylor College of Medicine and the chairman of its department of molecular and human genetics. “We know there are gene deletions associated with schizophrenia and with aggressive behavior. People are anxious not to stigmatize people with schizophrenia. But we also owe it to society to take a look.”

But what will finding that gene, or combination of genes and enzymes, tell us? Dr. Harold Bursztajn, a professor of psychiatry at Harvard Medical School, thinks it will only mislead the public and criminologists. “Even if we were to isolate a gene that shows a proclivity for aggression, how will that tell us who is going to become a serial killer or mass murderer and who is going to become a life-saving surgeon?” says Bursztajn, who advises on colleges admissions and see all sorts of behavioral inclinations. “It would be a tragedy for genetic research to get devalued by this idea.”

Even among criminals, types of aggression are as varied as motives. Rape is a crime of aggression, but is it the same sort of rampage as a mass killing? Serial killers often hunt and choose their victims, and carry out their violence over the course of years and even decades, often living seemingly normal lives among the rest of us. “When you look at Adam Lanza’s genome, you are looking at it because of a single act of behavior, the act of mass murder, and quite frankly, the final act of his life,” says Tissenbaum. “So you are looking at behavior. Well how do you measure behavior? And what types? The person who kills 20 kids in a day or one victim a year? People are hurting. They want an answer so bad they’re willing to put aside correct science.”

Further complicating the search for a “killer gene” is the fact that our genes don’t always express themselves in the same way. Diet, environmental stressors (like poverty or a bad home life or war), exposure to toxins, early nutrition—even in utero—all affect their expression, says Tissenbaum.

None of these concerns will stop scientists from looking for such genetic links. But their findings will certainly baffle society for generations to come. If a genetic explanation for violence is found, even one that suggests proclivity, what do you do with the people who have it? How do you identify them before they become violent? Do you screen kids before they enter school? Do you then administer gene therapies?

“There’s a real danger of creating a new eugenics,” says Harvard’s Bursztajn. “And there’s a danger of distracting people from the real causes of mental illness. There’s a wonderful Steven Spielberg movie with Tom Cruise, Minority Report, where Cruise for whatever reason is able to prevent crimes in the future. And of course, it all goes terribly wrong, as these sorts of things always will and always do.”

Photo: Saad Faruque

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Kevin Gray

Contributing Writer

Kevin Gray is a freelance writer based in New York. His work has appeared in The New York Times Magazine, New York, The Washington Post, Newsweek, Details and Men's Journal. Disclosure