So this immunity to mental illness that Muslims are apparently blessed with... anyone you know if there's been much research done on it? Seems to me that if they could figure out the underlying mechanism, it might be possible to develop some really effective treatments for mental illness and save a lot of suffering.

develop some really effective treatments for mental illness and save a lot of suffering.
Toni lavis,
Sounds fairly logical but eventually the Toni lavis's of this world would soon find fault with it as they do with all other measures based on logic.

Hold that thought Toni Lavis.

Psychopaths are not generally considered under the heading of mental illness.
Should we split hairs till the cows come home?

Look up “ fox in the henhouse syndrome” . Kill one kill many. Comes under the heading of economy.
No mental illness here. This is Mother Nature at work, (in strange ways as she does).

My answer is this: a mandatory life sentence for possession of a fire arm, applicable to all.

diver dan,
having a firearm is not as severe a breach of the Law than bureaucrats who don't do their job.

ISIS claimed credit for the suicide attack which, according to the currently approved meme, proves they have a mental illness...or something.

//ISIS claimed credit for the suicide attack//

Didn't they claim credit for the Las Vegas shooting as well? I wouldn't necessarily believe everything ISIS say... I reckon they make stuff up.

//which, according to the currently approved meme, proves they have a mental illness...or something.//

No, not every mass shooter has a history of mental illness. Stephen Paddock, the alleged ISIS-affiliated terrorist behind the Las Vegas shooting, didn't have a history of mental illness.

Faisal Hussain did. According to his family - and I'd assume they'd know, having lived with the bloke - he had a history of psychosis. Please note that psychosis and psychopathy are two very different diagnoses, despite the similarity in spelling. Here's a brief educational video about psychosis:

http://www.youtube.com/watch?v=hGP_7cEP5cI

The more you know...

Most psychotic people are harmless, but that isn't always the case. Sometimes psychosis can lead to violence. I recall a story I read years ago where somebody attacked their partner whilst in the grip of psychosis, believing that they were possessed by a demon of some sort. If Hussain was experiencing a psychotic episode - which seems at least plausible given a history of psychosis - then god knows what he was thinking when he carried out his attack.

Look, for all I know the guy was a fully paid up member of ISIS. I'm sure further details will emerge in the future. But at this early stage, to so readily dismiss the possibility that his mental health might have had aught to do with it.... well, that seems to me like its own peculiar form of madness.

But maybe I've been misreading my Sherlock Holmes books all these years, and Holmes' timeless advice on the art of deduction is to start by eliminating the possible.