There's not exactly a whole bunch of news going on right now. According to the Mail we are witnessing the "Invasion of the killer jellyfish" (except Portuguese men o' war have been reported on British shores since at least 2003), the hunt for the Yeti continues, and there's always room for another "equation for" story.

Somehow what doesn't get into the papers is as interesting as what does. Right now I'm looking at a press release on a story which seems pretty important to me: people with serious mental illnesses are committing fewer murders than ever before, by a truly enormous margin.

Homicides in this group increased from around 40 a year in the 1950s to 100 a year in the 1970s, in line with a similar increase in the general population.

But while murders by people like you have continued to increase, and roughly trebled (0.6 per 100,000 of population in the 1950s, and almost two per 100,000 now), murders by people with serious mental illnesses, despite the hype and the fear, the public pronouncements and the headlines, have come down massively since the 1970s, to fewer than 20 a year today.

Alongside the silly season stories, this startling new analysis of several different databases worth of information was not considered newsworthy. It got coverage in New Scientist (ooh) and BBC Online only. Nobody else touched it. What a mystery.

Journalists are traditionally fascinated by mental illness after all.

Celebrities with schizophrenia or depression can expect to have their hospital admissions (and embarrassing behaviour when unwell) diligently documented by the newspapers, and murders associated with mental illness receive blanket media coverage, with extensive campaigns both in the media and at grassroots level.

When the "mental health tsar" Louis Appleby called for more effort at reducing murders by people with serious mental health problems last year (a "bloke has opinion" story if ever I saw one) it was news to every single newspaper.

Journalists also love numbers - they use them for a spurious sense of precision, and for an air of scienciness - and this story had plenty, from a proper study, published in the British Journal of Psychiatry. Journalists also routinely take stories handed to them on a plate by press releases, as a quick scan of any newspaper will rapidly reveal.

According to research commissioned by Guardian journalist Nick Davies from Cardiff University, about 80% of news coverage is rehashed from them.

There is a crowd pleasing answer here, of course, which is that society is very simply prejudiced. But there is also a more mundane explanation. In a generous mood, you wouldn't say this was a very badly written press release, but it doesn't give the story on a plate, at first glance, with a populist headline, a catchy narrative to hang it on, the offer of photos (with breasts) and the idea that "stigmas and deep-rooted fears are misguided" flagged up in neon lights. You had to pay attention to find the news.

And it wasn't widely disseminated. My friend Nadia Stone writes positive stories about people with mental health problems (it's why we're friends).

There was one simple reason she didn't run with it: she gets plenty of nonsense from PR companies on pills and cosmetics, but the academic journal didn't send their press release to local papers, which often cover the very anecdotes that can wrongly calibrate peoples fears and prejudices.

"It might actually have been useful considering two men with schizophrenia escaped from a mental hospital near Exeter on Tuesday night, and everyone's been very scared."

We are convinced by the media that people with serious mental illnesses make a significant contribution to murders, and we formulate our approach as a society to tens of thousands of people on the basis of the actions of about 20.

Once again, the decisions we make, the attitudes we have, and the prejudices we express are all entirely rational, when analysed in terms of the flawed information we are fed, only half chewed, from the mouths of morons.