At one point a few days ago I feared to turn on the radio or TV because of the ceaseless accounts of blood, death and screams, one outrage after another, which would pour out of screen or loudspeaker if I did so.

And I thought that one of the most important questions we face is this: How can we prevent or at least reduce the horrifying number of rampage murders across the world?

Let me suggest that we might best do so by thinking, and studying. A strange new sort of violence is abroad in the world. From Japan to Florida to Texas to France to Germany, Norway and Finland, we learn almost weekly of wild massacres, in which the weapon is sometimes a gun, sometimes a knife, or even a lorry. In one case the pilot of an airliner deliberately flew his craft into a hillside and slaughtered everyone on board. But the victims are always wholly innocent – and could have been us.

We learn almost weekly of wild massacres, in which the weapon is sometimes a gun, sometimes a knife, or even a lorry. Pictured, a memorial for the victims of the Bastille Day attack in Nice

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

I absolutely do not claim to know the answer to this. But I have, with the limited resources at my disposal, been following up as many of these cases as I can, way beyond the original headlines.

Those easiest to follow are the major tragedies, such as the Oklahoma City bombing, the Nice, Orlando, Munich and Paris killings, the Anders Breivik affair and the awful care-home massacre in Japan last week. These are covered in depth. Facts emerge that do not emerge in more routine crimes, even if they are present.

Let me tell you what I have found. 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.

I know that many wish to accept the simple explanation that recent violence is solely explained by Islamic fanaticism. No doubt it's involved. Please understand that I am not trying to excuse or exonerate terrorism when I say what follows.

But 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 on Friday: '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.'

The Munich shopping mall killer had spent months in a mental hospital being treated (almost certainly with drugs) for depression and anxiety

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.

Here is my point. We know far more about these highly publicised cases than we do about most crimes. Given that mind-altering drugs, legal or illegal, are present in so many of them, shouldn't we be enquiring into the possibility that the link might be significant in a much wider number of violent killings? And, if it turns out that it is, we might be able to save many lives in future.

Isn't that worth a little thought and effort?

Vanishing websites - one more sign of America's madness

Whenever I am tempted to think (as I am often urged to do) that Donald Trump cannot possibly be as bad as he looks, I quickly learn that he is worse.

Everything about him is fake, even his fakery.

The website of his wife, Melania, suddenly vanished after an unauthorised biography suggested that she had embroidered her qualifications.

Why not either deny it or admit it? What madness has possessed Americans that they are even thinking of electing her husband?

Whenever I am tempted to think (as I am often urged to do) that Donald Trump cannot possibly be as bad as he looks, I quickly learn that he is worse

If a trendy charity announced that it was holding seminars for burglars, to show them how to avoid being hurt in the course of breaking into our homes, you wouldn't expect the police to approve. They may not care all that much about crime these days, but they'd have to put a stop to it.

Yet when a trendy charity offered to test illegal drugs for 'quality' at a music festival in Cambridgeshire, the local police gave their blessing. The 'tests' duly went ahead, and hundreds of squalid, selfish people went unpunished for blatant breaches of criminal law. All that users of illegal drugs need to know about quality is that they are dangerous. That's why it is illegal to possess them.

For drug-taking, like burglary, is not a victimless crime. The victims are the families of the users, who must often spend many years picking up the pieces of broken lives, and us, the taxpayers, who must look after them, too. Whatever we pay the police for (and this is increasingly unclear to me) we do not pay them to undermine the law in this way. The Cambridgeshire force should be reminded that their salaries and offices are funded by taxes that would not be paid if the law was not widely obeyed and enforced.

If they undermine the law, they undermine themselves.