While it is certainly true that most seriously mentally ill (SMI) individuals are non violent and in fact much more likely to be victims of violence than perpetrators of violence, it is also true that there are a small number of individuals with SMI determinations (10%) are in fact responsible for a disproportionate amount of community violence, including homicides.
All you have to do is look at a cross section of newspaper reports of homicide cases going back a few years to see a definite pattern here.
This is something, oddly enough, many professionals within the mental health industry don’t seem to want to admit or deal with for some reason?
In my own research major mental disorders, especially among schizophrenia (even without significant risk factors like substance abuse) are associated with a higher risk of interpersonal violence.
For example, when compared to the general population, men with schizophrenia had a two to five times greater risk of committing violent acts and women with schizophrenia had a four times greater risk than other SMI categories.
So there is a correlation between schizophrenia and violence that can’t be so easily dismissed.
Factors that put schizophrenics at increase risk of perpetrating acts of violence and murder include:
1) Substance abuse
2) Non treatment of mental illness symptoms and problems.
Based on the research l’ve seen people with substance abuse issues and untreated SMI are responsible for approximately 10% of all homicides in the United States (although l personally believe it is higher).
Unfortunately the US Justice Department, specifically the Federal Bureau of Investigation (FBI) doesn’t distinguish the SMI category from other homicides – so the true extent of the problem remains unknown.
See article: Homicide in Discharged Patients with Schizophrenia and other Psychoses http://www.schres-journal.com/article/S0920-9964(10)01465-9/abstract?cc=y=?cc=y=
See also: Schizophrenia and homicidal behavior http://www.ncbi.nlm.nih.gov/pubmed/8685666
See related article: Sandy Hook shooting’s glare illumines cracks in mental health care http://www.minnpost.com/christian-science-monitor/2012/12/sandy-hook-shootings-glare-illumines-cracks-mental-health-care
See article: Giffords Shooting Reveals Flaws in U.S. Mental Health Services http://www.care2.com/causes/giffords-shooting-reveals-flaws-in-u-s-mental-health-services.html#ixzz33aX4I3Qy
See article: Navy Yard gunman had history of mental illness, checkered military career, officials say http://www.washingtonpost.com/politics/alleged-navy-yard-gunman-had-checkered-military-career-officials-say/2013/09/17/a136ad0c-1fa1-11e3-8459-657e0c72fec8_story.html
See article: Mental illness issue surfaces in Colorado theater shooting case http://www.foxnews.com/us/2012/08/10/mental-illness-issue-surfaces-in-colorado-theater-shooting-case/
See video: 50% Mass shootings in US linked to Mental Illness http://www.youtube.com/watch?v=N7JIb_CaOvg
See video: 10 Mass shooting incidents http://www.youtube.com/watch?v=UeO5QTAryNE