When you focus a policy it has to be for a justifiable reason. In the case of focusing policy on mental illness to control gun violence, the question must be do the mentally ill represent a significantly different risk of gun violence from the general population. This is necessary because of constitutional protections for -all- citizens including the equal protection clause
The answer to whether there is such difference for all classifications of gun violence and all classifications of mentally illness compared to the general population is very decidedly -NO-.
When the question gets parsed into different pieces relative to the type of gun violence the answer for a role of mental illness in a specific type of gun violence is decidedly -YES-. Gun suicides are quite definitively linked to depression and anxiety.
But solitary gun suicides are not generally acts of social violence. Social gun violence is gun violence out in society, it includes things like the use of guns in robberies, road rage incidents, gang wars, terror attacks, that include intimidation and shootings in workplaces, schools, retail businesses and public spaces.
Social gun violence would be defined as gun violence that occurs outside of personal relationships, which are matters of domestic violence. Social violence general also excludes violence of persons held in institutions such as prisons, detention camps, and medical and psychiatric hospitals. Gun violence by the mentally ill in institutions is rare and what occurrence there is is outside consideration of "public" policies. Institutionalized persons with mental disorders are prohibited from firearms.
Broadly speaking social gun violence by the mentally ill is statistically uncommon and does not represent significantly increased risks over the general population, which in addition to non-mentally ill members of society also includes a very large number of perpetrators of criminal intimidation with guns, and smaller numbers of people who commit acts of gun violence during acute acts of anger, persons involved in gang violence, persons engaged in acts of terror/political intimidation/rebellion, and persons seeking vengeance, etc.
The public's concern about mentally ill and guns, as demonstrated by very limited concern about the largest category of gun violence--guns used to intimidate during crimes, and by comparison a hyperbolic concern about the acts of violence, is the role of mental illness in intentional mass gun murders in public places against random persons.
Even in this much narrower slice of gun violence in America the role of mental illness is not as clear as one might think, and doesn't clearly support building policies that focus on persons with mental illness.
Mother Jones constructed a database of such mass murders in the US incorporating publicly available information from the 1980s to 2012. Not all of them included guns, mass murders by car and by airplane were included. In that database, about 38% of the murderers could be linked to evidence of clinical mental illness (caveat: only ~20-25% of people seek clinical help for their mental health problems, although persons with more serious mental illness have a somewhat higher rate of help seeking--probably because their daily activities are more impacted by the disorders). Of the events recorded in the database near 60% of the murderers could be associated with 'some' history of symptoms which could be indicative of the presence of mental illness (caveat: symptoms of mental illness are qualitatively within the range of normal emotions, thinking and behavior, what makes them a disorder is the degree and duration of dysfunction brought about by those symptoms. Moreover, about 60 million Americans have some mental disorder each year, so a very large number of people who reach late adolescence and adulthood have experienced some symptoms of mental illness)
So what we can say is slightly more than half of mass murderers between the early 1980s and 2012 have -some- perceived association with mental disorders, although only about 1/3 of the mass murderers have records that would support that. About 66% of intentional mass gun murders in public places don't have a record of evidence that actually established presence of mental illness at all. And that uncertainty means that policies for reducing this specific type of gun violence can't be directed at any rationally narrowed group of mental disorders. Consequently, denial of civil rights to a class of people is very hard to justify in a way that meets court expectations of equal protection.
In recent years, suicide plus mass murder has been on the increase. Because suicide itself is definitively linked to mental disorders, it's very likely that these events are associated with mental illness. But it's not entirely clear -what- mental illness... depression? adjustment disorders? dramatic personality disorders--paranoid schizophrenia? bipolar disorder? borderline personality? What??
The number of these events is thankfully small, but that small size makes statistical significant association hard to obtain for any particular known mental disorder. And there is no reason at all to believe that the psychiatric industry has yet named -every- mental disorder that occurs. For example, Post Traumatic Embitterment, a disorder described in Germany (that includes what we in the US call going-postal) a disorder with good diagnostic clarity, and a disorder for which effective therapy exists, was intentionally left out of the new release of the APA's Diagnostic Manual, mostly it seems because professional reviewers didn't like the use of the terms 'post traumatic' in the name (they fear it is over-applied and would add confusion to PTSD).
How do legislators justify targeting a class of people who can't be shown to be accurately identified. Well they don't need any psychiatric medicine at all to justify policy. They can use public sentiment, which is to say, cultural bias and perhaps even prejudice against the mentally ill (in 2013 a survey was published that found 90% of Americans thought mentally ill shouldn't be institutionalized, but that same survey found 80+% of Americans didn't want a day care center for the mentally ill in their neighborhood, similar percents of Americans didn't want mentally ill persons as neighbors or on their team at work. In 2013, a national survey found that unemployment among the mentally ill was about 80). And public sentiment currently runs very strongly that mentally ill -ARE- the workable part of the problem of mass gun murders in public places.
What caretakers and advocates for persons with mental disorders and persons with mental disorders fear is further criminalization of mental illness and greater institutionalization of discrimination against persons with mental disorders under the rationale that -even the government finds them too dangerous to be treated as full citizens-.
I'm all for ending mass gun murders. If there were clear justification for identifying specific mentally illnesses as a significant part of the problem I'd be ok with targeting persons with those mental illnesses. But as it stands, even among persons with serious mental disorders just less than 7% per year engage in -any- non-institutional violence, which is just shy of 2 percent above the rate of any violent acts in the general population.
And to be clear, all this long reply is just to address the problem of trying to focus policy against persons with mental illness that have a clearly elevated risk so that any policy/law meets it's constitutional requirements.
What you posed is way to ambiguous to seriously evaluate for any specific benefit or harm
Problems with "history":
a) The restrictions are going to be very porous. Mental disorders emerge more commonly among people under 30, often people under 25, but mental disorders can emerge at -ANY- time, including -after- a person has bought a gun. Mental illnesses can also resolve and the numbers suggest that survival to middle age is associated with decline in mental disorders. So status of history may not reflect the status of present risk very well.
b) Most people, somewhere around 75% to 80%, with mental disorders do not seek or receive clinical help, people who don't seek clinical help CANNOT HAVE A HISTORY. About 20% of Americans are estimated to suffer from symptoms of a mental disorder annually...that's 60 million people or 1 in 5, that's a huge number of people to treat as criminals in-waiting. That attitude would have social consequences.
Problems with "mental illness":
a) there are -many- mental disorders, most of them have no association with violence, in society or in private. The net that can be cast with this approach can easily be over-sized and complicate rather than resolve the problem of identifying the small number of persons who indeed are potentially dangerous.
b) not every mental disorder is yet known or accepted as an authentic disorder. The APA rejected inclusion of a number of mental disorders when creating it's new edition of it's diagnostic manual, including rejection of an anxiety disorder characterized by 'embitterment' which includes heightened likelihood of acts of deliberate vengefulness.
c) The likelihood of a person with a diagnosed -severe- mental illness (schizophrenia, bipolar, borderline, etc) committing an act of violence in the US is estimated to be slightly over 6%. The likelihood of social violence among the general population is about 5%. Which is to say even for persons with severe mental illness there is not statistically significant elevated risk. Indeed the possibility of random mentally disordered person committing an act of social violence is almost exactly identical to the possibility of any randomly chosen gun owner.
Problems with this approach.
a) This approach has much to do with exploiting existing stigma about mental illness in American culture and the need to create scapegoats (the NRAs 'monsters among us') so that cognitive dissonance (aka discomfort) about our society being violent can be reduced.
b) This approach actually increases stigma and fear about people with mental disorders which results
1) in people avoiding clinical assistance with mental disorders because they fear the harm done by such a label.
--this adds to the problem of untreated persons in society
--it confounds the possible effectiveness of this strategy by increasing the difficulty of finding people with histories of mental disorder
2) in increased discrimination against the mentally ill.
In case you didn't know it...2012 unemployment in the US among persons with mental illness averaged about 80%. Discrimination in employment reflects discrimination in association across society and results in marginalization and isolation of persons with mental disorders. This destroys a basic early warning system for potential problems with mentally disordered by reducing opportunities for interventions in gun violence by friends, coworkers etc. to near zero.
Increased stigma and discrimination simultaneously is quite likely to exacerbate feelings of frustration and unfair persecution that motivate even the mentally well to embittered acts of such as revenge.
Analysis of the effectiveness of the NICS database in preventing purchases from banned persons is that those on the list have one of the lowest rates of violation. Persons with histories of mental illness don't violate NICS. The real violations are among persons with criminal histories.
Suicide remains a dominant cause of gun deaths in the US. But it is not the chief concern or target of gun control which is driven by fear of gun violence committed on innocent others. But it is a serious problem that needs attention.
The mental disorder it is most often associated with depression. Depression is also the most common of diagnosed mental disorders in the US, and it accounts for the majority of diagnosed mental disorders per year...about 70% of cases of depression are diagnosed in women...who have lower rates of both social gun violence and suicide than men.
Because of the high prevalence of depression, over their lifespans well over half of Americans experience it personally. If these persons sought clinical assistance and thereby were placed on NICs, it would create an enormous burden on the reporting system would add to its expense and would provide little benefit other than the psychological relief that comes from having done 'something'.
Criminalizing depression would once again, contribute to increased stigma and people's perception that they need to hide or deny symptoms of mental disorder in order to prevent the social costs of such a diagnosis. The result would be decreased help seeking...the very things we might expect to help reduce the occurrence of suicide and the very thing needed to make denial of gun purchases to a person with mental disorder possible.
It is quite clear that some persons with mental disorders can be a danger to themselves or others. Protecting them from themselves, and protecting the public from them is an obvious and long-standing concern. Social systems already exist to respond to such people. But stigma and discrimination often drive these cases underground, leaving more general passive policies, such as waiting periods for taking possession of guns, one of the few possible responses. As we have seen in handfuls of recent mass murder cases, long-term planning that exceeds waiting periods is often involved as is coming into possession of a firearm that was purchased by someone else.
Our perceptions of the significance and fear of gun violence vary with our context. This week end just in the city of Chicago, over 6 people were killed in acts of social violence and 27 wounded by guns. In my rural county in SE WI there were no gun murders and no people wounded.
There are people with mental disorders in both places and in about the same proportion. Murders by guns have occurred in my rural county, and just as elsewhere gun suicides are many times more common.
Those patterns have actually been confirmed by research across America. The problem of social gun violence has causes that don't really center on mental illness, even while recent high profile cases of suicide plus mass murder do.
Impulsive acts of violence are part of human nature. Defense of territory and property is a part of innate human social behavior as well as learned behaviors even within the culture of the criminally inclined. Availability of guns provides options for tool use that has increased deadliness for those behaviors.
Identification of strategies that reduce social/criminal gun violence shouldn't be based merely on the size of the public's fear...which can be a massive illusion based on frequency or salaciousness in the media.
Strategies should be decided based on the greatest potential for reductions in social gun violence returned per unit community investment. That won't always mean that the biggest root problems will be addressed, but rather control of the biggest root causes that can be effectively implemented. Those strategies have to reach deep and engage human social behavior.
Focusing effort and expenditures for control of gun violence on broad swathes of the subpopulation of persons with mental disorders risks poor and ineffective use of resources. It creates attitudes that essentially criminalize illness. It often seems less aimed at reducing real social gun violence than it is aimed at calming a society that misunderstands mental disorder and has an irrational fear of it