It is a huge problem that people with mental health issues go undiagnosed and untreated. It's also very disingenuous the same people who want to blame mental health for all gun related violence will do absolutely nothing to provide care for people with mental health issues AND actively oppose providing care.

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. That alone isn't conclusive of anything but when you do look at the data and it shows the exact opposite you have to question the original hypothesis.

Maybe, not generalizing all mental health to be the cause for people to be violent, would be a place to start? Possibly. Are there specific disorders that contribute whether or not someone is capable of violent acts? Who knows but I can guarantee to you the people pointing the finger at mental health do not care, in the slightest, to find out.