I have a mental health problem. A couple of them, actually. Attention deficit hyperactivity disorder is the big one. I was diagnosed at 26 and take medication daily for that. I also have some mild depression that comes and goes and is currently settled down on the couch with its shoes off.
But it’s nice to know I’m not alone. Nearly 47 million American adults — about 19 percent of us — deal with a mental illness of some sort. Serious mental illness, the kind that can keep people from being able to do normal life activities, is also pretty common: It affects 11 million American adults. Even with a specific, uncommon diagnosis like schizophrenia, you’re still talking about (at the low end of the estimates) some half a million Americans.
Almost none of us are mass shooters.
After the recent mass shootings this summer, President Trump said mental illness is a cause of violence and could be a predictive tool for spotting dangerous people. But that won’t work — there are just too many people who “fit the description” and too much confusion about what “the description” even means.
Take, for instance, the links between suicide and mass violence. Last week, I wrote a story about researchers’ findings that many mass shooters are also suicidal. None of this research compared perpetrators of mass violence to the general population, which is just the first of many reasons that the presence or absence of suicidal thoughts is not a great way to predict who will become dangerous. After the article was published, several readers asked me whether those findings meant that President Trump was right to blame mass shootings on mental illness and see institutionalization as a solution.
Short answer: Nope. He wasn’t.
First, you’ve got a problem with the statistics. There is evidence that people with severe mental illnesses, such as schizophrenia or bipolar disorder, do commit acts of violence at a greater rate than people who don’t suffer from those disorders. But that comes with some really big asterisks.
A couple studies have shown that most or all of that difference can be accounted for by whether or not the people in question have a substance abuse problem on top of everything else. And, more importantly, the difference is still so modest that it’s kind of useless as a predictor of violence. So, for instance, a 2011 study involving a survey of more than 34,000 people found that 10 percent of people with both a serious mental illness and a substance abuse disorder committed an act of violence in a given year — compared to about 0.8 percent of people with neither issue. But that still leaves a lot of nonviolent, mentally ill addicts in the world — enough that using those two factors alone as your predictor of violence would make you wrong nine times out of 10.
And that counts all types of violence — these totals don’t distinguish between, say, bar fights, throwing something at a roommate and threatening someone with a knife. Your likelihood of being wrong about someone’s propensity for violence goes up even more when you’re talking about specific, very rare types of violence like mass shootings.
Which brings us to our second problem: The definitional one. What does mental illness mean to you? Existing gun background checks and the president’s statements imply that the risks come from people with serious disorders, the kind of thing that we used to put people in institutions for. But that’s not what’s turning up as a characteristic among mass shooters. Instead, mass shooters often have the kind of mental health problems that are much more common and prosaic — plain old depression, personal crises, poor coping skills, and thoughts of or attempts at suicide.
Potential mass shooters aren’t easy to spot, but the contradictions in our logic about them are:
- The kinds of severe mental illnesses we’re so often afraid of don’t seem to be strongly associated with mass violence.
- The serious mental illnesses that are loosely linked with violence are still a poor predictor of who will become violent.
- The mental illnesses that seem to be common among people who commit mass violence aren’t good predictors of violence.
- And we have no idea how people who commit mass violence differ from the general population — we only know what they have in common with each other.
Americans would certainly benefit from being able to more easily and cheaply see a therapist or get mental health treatment when they need it. And the researchers I spoke with for my recent article do think access to that kind of care would reduce mass violence by helping some of the tiny fraction of people who might otherwise turn a suicidal tendency into a homical one.
But that’s not the same thing as saying that a diagnosis will help you find the Americans who are bad and scary and dangerous. And it’s certainly not the same thing as saying that you can prevent mass violence by taking those people and locking them away in an institution.
Just ask me. And nearly 47 million other Americans.
Maggie Koerth-Baker is a senior science writer for FiveThirtyEight. @maggiekb1