After Devin Patrick Kelley allegedly entered a church in Sutherland Springs, Texas last Sunday and shot dead 26 people, the conversation, prompted by politicians, immediately turned to mental health.

The "horrific shooting" represents a "mental health problem at the highest level", US President Donald Trump declared on Twitter, adding in a press conference that the attack "isn't a gun situation".

Trump's argument was bolstered when it was revealed that Kelley, 25, had "suffered from mental disorders" and had escaped a psychiatric hospital more than five years ago.

He was sent to the facility after being charged in a military court with assaulting his wife and fracturing his infant stepson's skull, according to documents obtained by local news channel KPRC.

Despite the revelations about Kelley's mental health, and the fact that the majority of Americans (63%) believe mass shootings in the US have more to do with mental health problems than gun control laws, health professionals warn that people should not draw a connection between mass shootings and mental illness.

"This is all a red herring," Liza Gold, a forensic psychiatrist at Georgetown University of Medicine and editor of the book, Gun Violence and Mental Illness said.

"The vast majority of mass shootings are not committed by the diagnosable mentally ill, no matter what politicians try to suggest," Gold said.

"Our country is in a state of denial about the real nature of gun violence and what we can do to decrease mortality."

Only about three to five percent of violent acts in the US are committed by individuals who have been diagnosed with a mental illness, and the percentage of crimes they commit with a gun "are lower than the national average for persons not diagnosed with mental illness," according to findings published in the American Journal of Psychiatry in 2015.

Studies have also found that the mentally ill are no more likely to become violent than a person without an illness, and that only one percent of violent acts committed by psychiatric patients involved killing a "target".

"If we were able to magically cure schizophrenia, bipolar disorder and major depression, that would be wonderful, but overall violence would go down by only about four percent," according to Jeffrey Swanson, a professor in psychiatry and behavioural sciences at the Duke University School of Medicine, told ProPublica in 2014.

The National Rifle Association (NRA), the most powerful gun lobby in the US, has capitalised on the public perception of the mentally ill.

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Following a mass shooting in Las Vegas, Nevada in early October that left 58 dead and more than 500 injured, NRA Vice President and CEO Wayne LaPierre also pointed to mental health.

"I mean, the outrage they're trying to stir against the NRA, they ought to be stirring against the mental health system, which has completely collapsed," he told CBS at the time.

Investigators have yet to reveal whether alleged Las Vegas shooter Stephen Paddock had a diagnosed mental illness.

'Accessibility is the real problem'

Michael Stone, a forensic psychiatrist at the Columbia College of Physicians and Surgeons and author of The Anatomy of Evil, has created a database of 350 mass murderers dating back over a century.

While Stone has found that around 20 percent of mass murderers have been severely mentally ill, he told Al Jazeera that the "real problem is accessibility" to guns.

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In the Texas shooting, Kelley bought the firearms he allegedly used through a federally licensed firearms dealer, where the seller is legally required to conduct a background check through the National Instant Criminal Background Check System (NICS).

His name was able to clear the system because the US Air Force admitted they failed to report Kelley's domestic violence convictions to the FBI - a conviction that, according to federal law, bars an individual from buying a firearm.

Researchers say, however, that even if Kelley's history had been reported to the FBI, he would have still had a way around the system as not all legal firearm purchases in the US require a seller to conduct a background check, fill out a form, or even show ID.

Currently, US federal law only mandates background checks from firearm retailers with a federal license to sell. For private sales that involve a seller without a federal license, including those at gun shows, only 19 out of 50 US states mandate a background check or a license or permit to buy a firearm. Texas is not one of them.

According to a 2010 Department of Justice report, "...individuals prohibited by law from possessing guns can easily obtain them from private sellers and do so without any federal records of the transactions".

Gun control advocates highlight this "loophole", and push for a federal mandating of background checks for all firearm purchases, private, unlicensed or otherwise, an idea commonly known as "universal background checks".

"Do they work? Millions of background checks have been denied, which suggests they work," said Eric Ruben, an adjunct professor at the NYU School of Law and fellow at the Brennan Center for Justice whose work focuses on weapons law and the Second Amendment.

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"Of course, they are not everything … but they likely increase the cost of guns on the black market, which is a good thing. And they are the best way I've heard to enforce the gun prohibitions that are central to current gun regulation in America."

While the NRA has argued that proposals such as these "would deprive individuals of due process of the law", Ruben disagrees.

"Such policies are perfectly consistent with the Second Amendment. In fact, I know of no case in which background checks have been challenged successfully," Ruben told Al Jazeera, adding that background checks only help to "implement bans that themselves are widely viewed as constitutional".

'Inherent contradictions'

Despite the NRA's efforts to lobby against expanding gun laws, studies from both the Pew Research Center and the Johns Hopkins Center for Gun Policy and Research have found that the majority of Americans (77 percent to 85 percent, respectively) support background checks for private sales along with other gun-control measures.

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"But we're left with a very politically challenging situation here," Stone said.

The NRA argues that "mental illness", not guns or background checks, should be "the focus of any policy to address high-profile shootings". But health experts point out that the organisation is also against expanding NICS to include "psychiatrist's diagnosis, a doctor's referral, or the option of a law enforcement officer … or seeking mental health treatment".

Including these individuals would be overreaching and "doing so would actually discourage troubled people from getting the help they need", according to the NRA's website.

Analysts and researchers also highlight that while politicians are quick to blame mental health for mass shootings, Trump and other pro-gun politicians have not said they will increase funding for healthcare providers or mental health research.

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In his first months in office, Trump repealed a regulation, implemented by the previous administration, that banned gun sales to individuals with certain mental health diagnoses, including those receiving Social Security checks for mental illnesses.

"There is so much inherent contradiction from all these people that it really boggles the mind," Georgetown University's Gold said.

"Mass shootings attract wide attention, but once you yell 'mental illness', no one even wants to consider evidence-based, sensible gun reform that could actually make a difference without infringing on gun rights," she added.

"The NRA has been very successful in creating a learned helplessness and denial that benefits them and not anyone else."