The next time someone blames mass shootings on mental illness, send them this.

As thousands across the nation prepare to take to the streets on March 24, 2018, for The March for Our Lives, we're taking a look at some of the root causes, long-lasting effects, and approaches to solving the gun violence epidemic in America. We'll have a new installment every day this week.

In the winter of 2012, an undergraduate student who'd just taken my abnormal psychology course sent me an email.

The note was short, containing a link to an article about Adam Lanza (the Sandy Hook shooter) and two questions: Did mental illness drive him to do what he did? And if so, did that mean that what I'd told her in class, that the mentally ill were no more dangerous than the rest of the population, wasn't true?

It's a question I've heard with alarming frequency since.

By now, it's like clockwork: A tragedy happens, thoughts and prayers are deployed, gun control is quickly shouted down ("No way to prevent this!" and "Now is not the time to speak about gun reform!"), and then top politicians — including the president — demand and vow to treat mental health as a top issue.

Photo by Scott Olson/Getty Images.

It all seems so intuitive. Because committing murder with an assault weapon isn't something most people would do, mental illness must be the cause.

"So many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior," President Donald Trump tweeted shortly after the Parkland shooting in February.

But Trump offered no criteria for the shooter's mental illness. Nor did he recognize that mental illness has never been one thing. And he ignored the painful reality that conflating mental illness with violence stigmatizes the millions of people worldwide who live with psychiatric disorders.

He wasn't the only one: In a Washington Post poll conducted right after Parkland, 57% of responders cited "problems identifying and treating people with mental health problems" as the driving force behind mass shootings. "Inadequate gun laws" received only 28% of the vote.

Whenever mental illness is brought up, we act as if the conversation were over. It shouldn't be.

As a country, we know very little about mental illness. In fact, a recent study out of Michigan State University found that under 50% of respondents could identify signs of anxiety, a condition experienced by fully 18% of American adults. And most people had no clue about how depression was treated.

This lack of knowledge keeps us scared. It turns every psychiatric condition into a boogeyman that's lurking around the corner. And it makes those of us who live with mental illness hesitant to talk about our conditions openly to provide more knowledge.

That's right: us. I don't just teach and write about psychology; I've lived with depression and anxiety since I was a teenager.

And while I agree that mental health reform needs to take place, it's not because people who live with the conditions I do — or a multitude of other conditions — are more dangerous to others. It's because the system makes it so hard for so many to get help.

It's because so many people (up to 47%, according to a 2013 survey) would feel uncomfortable living close to someone with a "serious" mental illness. Most of them don't even know what a "serious" mental illness is.

The truth is that gun violence isn't a result of mental illness. But mental illness is an easy scapegoat.

A sign outside Marjory Stoneman Douglas high school in Parkland, Florida. Photo by Rhona Wise/AFP/Getty Images.

As the Kaiser Family Foundation noted in 2013, it is impossible to know what kind of backlash mass shootings like the one that occurred at Sandy Hook (and the ones that have since happened in Las Vegas, Orlando, and Parkland) create against innocent people.

The mentally ill are no more dangerous than the rest of the population.

I get it. There's got to be a reason why bad people do awful things. We need something to grab onto in the wake of a tragedy. That's why one of the first places our brains go is mental illness.  

The results of a 2006 survey indicated that 60% of Americans believed that those living with schizophrenia were more likely to commit violence. A worrying 32% thought the same of those living with depression. It's why the news was so quick to seize upon the fact that Las Vegas shooter Stephen Paddock had been prescribed anti-anxiety medication, even though there's no evidence that it made any contribution to his crimes.

The reality is much more complex. While it's possible that those living with schizophrenia or bipolar disorder may be slightly more likely to engage in violent behavior (not necessarily with firearms), getting rid of these disorders would prevent a tiny slice of violence at best.

Dr. Jeffrey Swanson, a psychiatrist, professor, and researcher who studies the connection between mental illness and violence, told ProPublica that curing mental illness would only stem violence by 4%. "Most violence in society is caused by other things," he said.

A 2001 study of adolescent mass murderers found that only 1 in 4 had any sort of psychiatric history. That's a worrying number to be sure, but it was far outmatched by their seemingly "well" counterparts. And Michael Stone, a forensic psychiatrist who maintains a database of mass shooters through the years has found that out of 350 mass killers, 65% had no history of severe mental illness.

His conclusion? That it's not the mental illness that's the problem. It's how much access the individual has to guns.

"In my large file of mass murders, if you look decade by decade, the numbers of victims are fairly small up until the 1960s," Stone told The New York Times in 2017.  "That's when the deaths start going way up. When the AK-47s and the Kalashnikovs and the Uzis — all these semiautomatic weapons, when they became so easily accessible."

A 2015 article published by The American Psychiatric Association found that "mass shootings by people with serious mental illness represent less than 1% of all yearly gun-related homicides." The authors concluded that mass shooters were "unlikely to have psychiatric histories" and that focusing only on the mentally ill when considering gun control would be ineffective, considering the small size of the group.

And a 2003 paper published in World Psychiatry notes that "mental disorders are neither necessary nor sufficient causes of violence. Major determinants of violence continue to be socio-demographic and economic factors."

It's a cold and inconvenient truth: Gun restrictions placed only on the mentally ill wouldn't change gun violence as we know it. They may not even make a dent.

As the #NeverAgain movement has reminded us over and over: Gun reform on a large scale is the only way we'll transform the problem.

Of course, more research would be great too. But a 1996 spending amendment prevents the Centers for Disease Control and Prevention from using federal funds to conduct studies that would "advocate or promote gun control."

A student participates in the 17-minute walkout on March 14th. Photo by Justin Sullivan/Getty Images.

There are many more people living with mental illness than you'd probably guess.

Think about how many people you know. Now consider how many of those people may be struggling with their mental health in some way.

You're probably greatly underestimating that number. That's not just because there is a wide range of psychiatric disorders; it's because you can't tell who is mentally ill just by looking at them (that's just one of many myths) and because of the stigma those who live with these disorders face.

A 2003 survey conducted in England found that 60% of people believed only 10% of the population would be affected by mental health problems in their lifetime. But that's simply not true. Depression, for instance, is now reported to be "the leading cause of disability worldwide" by the World Health Organization. It affects more than 300 million people on Earth. And the National Alliance on Mental Illness reports that 18.5 million adults (that's 1 in 5) experience a mental disorder in any given year.

Do those numbers tell you something? They should.

Considering the disparity between the number of people who live with mental illness and the number of people who commit mass shootings, there's no way that we can blame the majority of gun violence — or any violence — on this group of people.

Those who are mentally ill are actually more likely to be victims of violence than perpetrators. They're also more likely to hurt themselves. As Bright Magazine notes, "mental illness plays a role in two-thirds of American gun deaths."

But those deaths aren't a result of mass shootings or homicide. They're the result of people with mental illnesses dying by suicide.

And that's why mental illness can't be the scapegoat.

If we're ever going to overhaul the mental health system, the first thing we need to do is create a climate where talking about mental illness isn't stigmatizing. Trump was proof that such an environment doesn't exist when he referred to the mentally ill as "sickos" while demanding we put more guns in schools:

It's in our nature to try to remove uncertainty. That's just the way humans work. And it's especially true when we consider gun violence. In the wake of a mass tragedy, we need some reasoning to grasp onto. Something that can point to a cause.

But just as "mental illness" is too broad a label to put on the myriad conditions and syndromes of its sufferers, correlating mass shootings to it only serves to other the millions that live with mental illness daily, making them feel (and be treated as) less-than. It's an incorrect conclusion drawn by oversimplification.

Here's how I try to talk about mental illness in my lectures: There's an insurance commercial I love (but can no longer find — that's how it always seems to go, right?). In it, a good driver is celebrated by color commentators, who gleefully yell about the driver using signals and turning correctly.

The idea is that we often don't reward people for their good behavior, that we only focus on the bad. It gives me a good feeling.

I mention this commercial because focusing on the bad is exactly what we do when we discuss mental illness. Where are the news stories that celebrate the ordinary people who are doing their best while living with anxiety and depression? The people who have stable lives because they're treating their schizophrenia? Because they see a therapist? Considering the numbers, they absolutely exist.

But the only time we discuss mental health as a nation is in the wake of these tragedies, when baseless accusations trump facts. When it's easy to point fingers.

And when "mental health reform" is used as a convenient way to sidestep the role that assault weapons play in mass shootings, we all suffer.

All of us deserve better than that.

• How the U.S. put an end to plane hijacking and why gun reform advocates should take note.
• Parkland kids are changing America. Here are the black teens who helped pave their way.
• Dear America: Kids doing active-shooter drills is not normal.
• Answer 3 questions to find out which gun violence action plan is right for you.

And see our coverage of to-the-heart speeches and outstanding protest signs from the March for Our Lives on March 24, 2018.