Memes

Despite all of that, if mental health was truly the main driving force behind mass shootings you would expect a higher rate of violence among the documented populous of people with mental health issues.

There is. There is no question that mental illness strongly correlates with a propensity for violence.

From the source:

A meta-analysis of 204 studies of psychosis as a risk factor for violence reported that “compared with individuals with no mental disorders, people with psychosis seem to be at a substantially elevated risk for violence.” Psychosis “was significantly associated with a 49%–68% increase in the odds of violence.”

A review of 22 studies published between 1990 and 2004 “concluded that major mental disorders, per se, especially schizophrenia, even without alcohol or drug abuse, are indeed associated with higher risks for interpersonal violence.” Major mental disorders were said to account for between 5% and 15% of community violence.

Among 3,743 individuals with bipolar disorder, 8.4% committed violent crimes compared to 3.5% of the general population in Sweden.

A 2014 study in Israel identified 3,187 patients with a diagnosis of schizophrenia. They committed four times more violent crimes compared to the general population, and this difference was even more pronounced among women.

A 10-year follow-up of 1,056 severely mentally ill patients discharged from mental hospitals in Sweden in 1986 reported that "of those who were 40 years old or younger at the time of discharge, nearly 40% had a criminal record as compared to less than 10% of the general public." Furthermore, "the most frequently occurring crimes are violent crimes."

The best study used the Danish psychiatric case register, covering the whole country, and convictions for criminal offenses. Between 1978 and 1990, 6.7% of males and 0.9% of females with "major mental disorders" (psychoses) were convicted of a violent crime ("all offenses involving interpersonal aggression or a threat thereof") compared with 1.5% of males and 0.1% of females among individuals with no psychiatric diagnosis.

A Swedish study examined the criminal records of all individuals born in Stockholm in 1953 and still living in the city 30 years later. Men and women with severe mental illness were 4.2 times (men) and 27.5 times (women) more likely to have been convicted of a violent crime compared to individuals with no psychiatric diagnosis.