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After every horrific mass shooting and disturbing terrorist attack, the reflex is the same: The attacker(s) must be mentally ill.

The shocking randomness of these acts is destabilizing, so simplistic conclusions may provide comfort, but you can't explain away violence by saying the perpetrators are "nuts."

Doing so does a grave disservice to those who do suffer from mental illness – the vast majority of whom are not violent – and it prevents us from discussing the complex personal, political and social drivers that create angry, young (for the most part) men.

Read more: Mentally ill people need to be calmed down, not shot

What leads someone to methodically gun down strangers from a hotel balcony, drive a truck into a crowd of people at high speed, or strap a bomb to himself and detonate it in a crowded restaurant is not easily understood or explained.

But what we can do is try to avoid sweeping generalizations and stereotyping and the creation of bogeymen like the religious fundamentalist afflicted by mental illness.

Recently, the French magazine Le Point published an extensive series of articles under the deliberately provocative headline: "Les djihadistes sont-ils fous?" (Are jihadists crazy?)

The polemic was sparked by comments made by French Interior Minister Gérard Collomb, who said that one-third of terrorists have "psychological issues" and called on psychiatrists and psychiatric hospitals "to identify the kind of personalities that could potentially take radical action."

Most psychiatrists responded indignantly. First of all, a "psychological issue" is not the same as a diagnosed mental illness; nor does a history of psychological/psychiatric illness predispose a person to violence.

Expecting psychiatrists or other health professionals to single out people who have the potential to be terrorists and/or mass murderers is preposterous. Health professionals already have the ethical/legal responsibility to identify people who are an imminent risk to harm themselves or others, but broader, predictive profiling would be a dubious exercise at best.

Are some people who commit terrorist/violent acts mentally ill? Of course.

There is some evidence that groups like the Islamic State try to recruit people who are unstable or mentally ill, because they are easier to manipulate.

We know too that hyper-religiosity can be a symptom of people with severe, untreated schizophrenia, and that psychosis can lead to delusions and violence. Extensive media coverage of radicals and terrorism can "inspire" these very sick people.

The case of Chiheb Esseghaier, who was convicted of eight terrorism-related charges for plotting to blow up a train bridge between Canada and the United States, is a good example of this phenomenon. But the case is also a reminder that suffering from mental illness is not a "get out of jail free" card, as some perceive.

People who are mentally ill are still responsible for their actions, with very few exceptions.

Let's not lose sight of the fact either that those who are not mentally ill are responsible for most of the heinous, murderous acts that make headlines.

A study published recently by Emily Corner and Paul Gill, both of University College London, examined 55 attacks by 76 individuals influenced by IS between May, 2014 and September, 2016 found that 27.6 per cent were perpetrated by people with a "history of psychological instability."

The authors note that is equivalent to the rate of mental illness in the general population – about one in five – and point out the figure is probably overstated because a lot of claims that shooters/bombers are mentally ill come retrospectively and often consist of speculation by police or family rather than actually diagnoses.

In their paper, published by the Combating Terrorism Center at West Point, the researchers caution against seeking a single "silver bullet" explanation for why people commit violent acts.

"Many individual cases share a mixture of personal life circumstances coupled with an intensification of beliefs that later developed into the idea to engage in violence," they write.

But how and why the process unfolds is unclear. The contributing factors, and triggers, are many: Depression, social isolation, anger, feeling jilted, fascination with weapons, and so on.

"Mental-health problems are undoubtedly important in some cases. Intuitively, we might see how in some cases it can make carrying out violence easier," Ms. Corner and Mr. Gill write. In other cases, it may make the adoption of an ideology easier because of delusional thinking or fixated behaviours. However, it will only ever be one of many drivers in an individual's pathway to violence."

In short, the link between mental illness and violence is labyrinthine, and we do ourselves no favours by reducing it to a caricature.

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