Beliefs are always about desire, and often also about fear, which makes those beliefs more passionate.

The atheist doesn't want there to be a God, but fears that there is one and so is constantly angry with believers, patrolling the Internet in search of a Christian to insult. Our current beliefs about terrorism, likewise, are driven by the desires of politicians and huge, expensive 'security services' (as they like to call themselves), to justify their existence, their excessive powers of surveillance and detention and their enormous budgets. They fear that, if the urgency of their task is questioned, their whole existence might also be questioned and they might need to find something else to do, where people would not take them so seriously or pay them so much.

This is all made worse by Crowther's Law, the first rule of journalism laid down by Geoffrey Crowther, sometime editor of the much over-rated Economist magazine. It runs: "Simplify, then exaggerate." Add to that the demands of rolling news TV channels, with their incessant desire to fill our screens with huge red rectangles yelling 'BREAKING NEWS', in the hope that they will keep us watching. It is a regrettable fact that these channels thrive on the melodrama of disaster and wilt during periods of calm.

And so we come to our current rather uninformative hysteria about the terror threat. Of course, there is a terror threat. This is undeniable. And for those it strikes, it is a frightful thing. What is more, much of it originates among fanatical Islamists. I state these incontestable facts because I know that what I am about to say will cause some people to lie about me, and claim that I am apologising for, minimising or defending Islamist terror. I am not. As a Christian and a Zionist, I have absolutely no reason to do so. As someone who has strayed (very unwillingly) into the edges of war zones, I know what a human head looks like after a bullet has passed through it and so have a horror of violence, and a sympathy for its innocent victims, as great as anyone's.

But. Yes, there was always a 'but' lurking behind that introduction, and here it is. We may be reacting to terrorist outrages in the West in an unintelligent and thoughtless way. We might help ourselves more if we took a slightly more analytic view of events which, if properly studied, might lead us to take different and additional precautions. Specifically, we should wonder whether we have been wise to abandon the laws against possession and use of mind-altering drugs, and indeed whether we are too complacent about the side-effects of prescription drugs now being widely issued.

Oddly enough, the same could be said of our invariable response to the generally non-political massacres and other outrages which take place in the United States. I believe that these events may be more closely related to the terror incidents in Europe than we have so far understood. The facts, when examined, undermine the idea, much beloved of security chiefs and media alike, that terrorist acts are driven by a some organised octopus of trained and disciplined militants, directed from a bunker in Iraq by a bearded, turbaned mastermind. Many of those involved are actually or nominally Muslim. But these may not be the most decisive feature in these individuals' choice of murderous violence. The facts also rather undermine the idea that relaxed gun laws (though obviously significant) are the prime cause of massacres in the USA. Such gun laws have existed for centuries, but these types of killings are recent.

There is something else, another variable which, once sought, is extraordinarily persuasive. Here I will quote from a recent article I wrote for the Mail on Sunday, which summarises what I have found through examining the backgrounds to a large number of rampage killings across the Western world.

"Timothy McVeigh, the 1995 Oklahoma bomber, used cannabis and methamphetamine. Anders Breivik took the steroid Stanozolol and the quasi-amphetamine ephedrine. Omar Mateen, culprit of the more recent Orlando massacre, also took steroids, as did Raoul Moat, who a few years ago terrorised the North East of England. So did the remorseless David Bieber, who killed a policeman and nearly murdered two others on a rampage in Leeds in 2003.

"Eric Harris, one of the culprits of the Columbine school shooting, took the SSRI antidepressant Luvox. His accomplice Dylan Klebold's medical records remain sealed, as do those of several other school killers. But we know for sure that Patrick Purdy, culprit of the 1989 Cleveland school shooting, and Jeff Weise, culprit of the 2005 Red Lake Senior High School shootings, had been taking 'antidepressants'.

"So had Michael McDermott, culprit of the 2000 Wakefield massacre in Massachusetts. So had Kip Kinkel, responsible for a 1998 murder spree in Oregon. So had John Hinckley, who tried to murder US President Ronald Reagan in 1981 and is now being prepared for release. So had Andreas Lubitz, the Germanwings pilot who murdered all his passengers last year. The San Bernardino killers had been taking the benzodiazepine Xanax and the amphetamine Adderall.

"The killers of Lee Rigby were (like McVeigh) cannabis users. So was the killer of Canadian soldier Nathan Cirillo in 2014 in Ottawa (and the separate killer of another Canadian soldier elsewhere in the same year). So was Jared Loughner, culprit of a 2011 mass shooting in Tucson, Arizona. So was the Leytonstone Tube station knife attacker last year. So is Satoshi Uematsu, filmed grinning at Japanese TV cameras after being accused of a horrible knife rampage in a home for the disabled in Sagamihara."

That was not all. Many terrorist perpetrators are in fact petty criminals living irreligious lives of dissipation, theft and dishonesty, very far from the current fantasy of the 'radicalised' fanatic taking orders from Islamic State. As I wrote: "When I checked the culprits of the Charlie Hebdo murders, all had drugs records or connections. The same was true of the Bataclan gang, of the Tunis beach killer and of the Thalys train terrorist. It is also true of the two young men who murdered a defenceless and aged priest near Rouen last week. One of them had also been hospitalised as a teenager for mental disorders and so almost certainly prescribed powerful psychiatric drugs. The Nice killer had been smoking marijuana and taking mind-altering prescription drugs, almost certainly 'antidepressants'.

"As an experienced Paris journalist said to me: 'After covering all of the recent terrorist attacks here, I'd conclude that the hit-and-die killers involved all spent the vast majority of their miserable lives smoking cannabis while playing hugely violent video games.'

"Now look at the German events, eclipsed by Rouen. The Ansbach suicide bomber had a string of drug offences. So did the machete killer who murdered a woman on a train in Stuttgart. The Munich shopping mall killer had spent months in a mental hospital being treated (almost certainly with drugs) for depression and anxiety."

The above catalogue is not complete and excludes some cases which will eventually, in my view, need to be included in it – once the facts are fully known. This variable is the rapidly increasing use in our society of potent mind-altering drugs, in some cases legally on prescription, in some cases illegally.

These drugs are now so common that we have begun to regard them as normal. Most people who take them do not become mass murderers or terrorists. The reason why I have been able to discover the drug use of such people is precisely that these mass killings attract so much media and official attention that the drug use by the culprit is known. They are a special subset of violent crime about which far more is known than is known about most violent crime. In thousands, possibly millions of lesser violent crime, the authorities and the media are uninterested in the perpetrator's drug use and it is not known. But the fact that some do might make us wonder about whether they are in general as safe or as beneficial as many of us believe.

I am not saying that all terrorists are drug users. I am not saying that all drug users are terrorists. I am not saying that Islam is not involved in terror. Yet I guarantee that some people will read this and claim falsely that I am saying all these things, as I have many times found when I have made this case in the past. This is because they want, for various reasons, to believe in the Terror Octopus myth, or (in some cases) because they fear any debate about the safety of drugs they may have used themselves. I wonder why.

Peter Hitchens is a columnist for the Mail on Sunday and author of The War We Never Fought – the British establishment's surrender to drugs. He blogs at http://hitchensblog.mailonsunday.co.uk/