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Adam Lanza’s DNA Will Tell Us Nothing

Genetics is a powerful tool, but it will not tell us why Adam Lanza killed those people

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Geneticists have decided to analyze the DNA of Adam Lanza, the 20-year-old who shot and killed himself along with 27 other people, including his mother and several children and teachers at Sandy Hook Elementary School.

The hope is to find something in Lanza’s DNA that will provide clues into his violent actions. The New York Times writes:

The researchers, at the University of Connecticut, confirmed their plans through a spokeswoman but declined to provide details. But other experts speculated that the geneticists might look for mutations that might be associated with mental illnesses and ones that might also increase the risk for violence.

They could look at all of Mr. Lanza’s genes, searching for something unusual like gene duplications or deletions or unexpected mutations, or they might determine the sequence of his entire genome, the genes and the vast regions of DNA that are not genes, in an extended search for aberrations that could determine which genes are active and how active they are.

But not everyone is convinced. That same New York Times article points out that mental illness is complicated:

Everything known about mental illness, these skeptics say, argues that there are likely to be hundreds of genes involved in extreme violent behavior, not to mention a variety of environmental influences, and that all of these factors can interact in complex and unpredictable ways.

“It is almost inconceivable that there is a common genetic factor” to be found in mass murders, said Dr. Robert C. Green, a geneticist and neurologist at Harvard Medical School. “I think it says more about us that we wish there was something like this. We wish there was an explanation.”

Instead of an explanation, DNA tests are likely to simply provide fodder for fear and discrimination. Already the entire discussion of Lanza’s possible autism has stigmatized autistic people (a diagnosis that has never been linked with violence). Robert Nussbaum, a geneticist at the University of California, San Fransisco, told Bloomberg:

“It’s a shot in the dark that’s unlikely to show anything,” Nussbaum said in a telephone interview yesterday. “If they find something associated with autism, I’m afraid that it might have the effect of stigmatizing autistic people. I can see a whole morass coming out of this.”

This isn’t the first time society has turned to genetics to answer some unanswerable questions. In 1966, a man named Richard Speck broke into a dormitory in Chicago and tortured, raped and killed eight nurses.

Around that same time, geneticists began looking at the genes of patients in a security hospital in Scotland. Nine of those patients had XYY syndrome, a condition in which a male has two Y chromosomes, that occurs in around 1 in every 1,000 males. These researchers concluded, incorrectly, that perhaps XYY predisposed men to be violent.

There are very few signs of XYY—most people never even know they have it—but for some reason men with the syndrome tend to be taller than average. Speck was taller than average, and one geneticist suspected that perhaps Speck had XYY. While a genetic test found that he didn’t, several newspapers reported that he did, and the incorrect story became a media sensation. There was even talk of screening children for the syndrome, to weed out potential criminals.

There was also the case of the “warrior gene” that claimed to show who might be more aggressive.  Scientific American sums that one up:

Obviously, the warrior gene cannot possibly live up to its name. If it did, the whole world—and China in particular, if the racial statistics cited above are remotely accurate—would be wracked by violence. The warrior gene resembles other pseudo-discoveries to emerge from behavioral genetics, like the gay gene, the God gene, the high-IQ gene, the alcoholism gene, the gambling gene and the liberal gene. (See my previous columns on the liberal gene and gay gene.)

The abysmal record of behavioral genetics stems from two factors. First, the quest for correlations between thousands of genes and thousands of traits and disorders is prone to false positives, especially when traits are as squishy as “aggression” and “childhood trauma” (the variable that helps some researchers link MAOA-L to violent behavior). Second, the media—including respected scientific journals likeScience and PNAS as well as shows like Dr. Phil—are prone to hyping “discoveries” that will attract attention.

Which brings us back to Adam Lanza. The bottom line is that we will never know why he did what he did. Slate writes:

We just don’t know, and we will never know. And even if we could know all the disturbing details of a killer’s psychiatric history—as we know some of the details about James Holmes, who killed 12 people in an Aurora, Colo. movie theater—it still wouldn’t likely help anyone prevent a future crime from happening. These cases are outliers, hardly typical. Unless a psych patient literally tells you of a homicidal plan that he intends to act on, it is often impossible to predict who is actually a threat and who isn’t. Many psychiatric experts have said that this shooting represents a deficiency in our mental health care system, but though we certainly have such deficiencies, it hasn’t been shown that Lanza was resisting treatment or even that if he was being treated properly, he wouldn’t have committed the murders. One of my colleagues, a top psychiatrist and psychoanalyst, had one of his patients jump out the window of his office a decade ago. My friend spent the next 10 years trying to figure out what he had done wrong before concluding that no matter what he had done, it wouldn’t have prevented this tragedy from happening.

Genetics is a powerful tool, but it will not tell us why Adam Lanza killed those people.

More from Smithsonian.com:

Can Your Genes Predict When You Will Die?

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About Rose Eveleth
Rose Eveleth

Rose Eveleth is a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.

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