Jon Ronson insists he isn’t a man who goes looking for trouble, but it certainly has a habit of finding him. In his award-winning career as a journalist and documentarymaker, he’s been unmasked as a Jew in a Jihad training camp, infiltrated a secretive ritual involving some of the world’s most powerful people, joined the Ku Klux Klan on tour and, most recently, found himself face-to-face with several psychopaths, all in the name of work.

Just the other week, while researching a piece for American GQ magazine, the married father-of-one wound up in a dark corner of Seattle at 4am, surrounded by armed crack dealers. “It was ridiculous and a big mistake.

I thought to myself, ‘I’m 43 and I’ve reached the end’.”

He doesn’t want to get into such situations: “I’m the least equipped person to do dangerous stories. I take no joy in it at all. The problem is, you have to go where the story takes you.”

From his bestselling 2002 book, Them: Adventures With Extremists, when he stepped into the worlds of religious fundamentalists and conspiracy theorists, to Hollywood film The Men Who Stare At Goats, which tells the true story of the New Age US army unit who believed they could kill goats just by looking at them, Ronson has set himself up as someone who will bravely go where the more sensible fear to tread, disarming people with his owlish appearance and apparent naivety.

He explains it as a desire to travel to someone else’s world and stand with them as they stare back at “us”. “It’s as much about understanding our world as theirs. It has to be or it’s just a freak show. I’d never go to a far-out place or visit a far-out person if it was only about that.”

Ronson’s latest book The Psychopath Test starts out in familiar territory as he meets Broadmoor inmate Tony, who claims to have faked a mental disorder to avoid a heavier sentence but is now stuck there, unable to convince anyone he is, in fact, sane. How, Tony asks, do you walk or sit or talk “normally”?

And if a sane man can convince psychiatrists of his madness, how can the system be trusted?

It emerges that while Tony might not be mad, in successfully faking mental illness, he has given himself away instead as a psychopath. As Ronson writes: “Tony faking his brain going wrong was a sign that his brain had gone wrong.”

What’s more, while Tony is safely incarcerated, others of his ilk appear to be roaming the corridors of power.

Ronson finds himself embarking on a disorientating journey that takes in misguided psychological experiments, the media exploitation of the mentally unwell, the role of psychopaths in a capitalist society and manicdepressive babies.

Far from being a detached observer, Ronson’s style has always been to jump into a situation feetfirst in the gonzo tradition. “I am a humorous journalist out of my depth,” he yelps to the British Embassy in Them, when a trip to Portugal to investigate the shadowy Bilderberg Group turns sinister.

Here, his research leaves him power-crazed and obsessed with identifying psychopaths. Yes, Ronson admits, it got somewhat out of hand. Friends and colleagues had started to express alarm. But he counters, “I just thought they were naïve. I was convinced I had the knowledge and they didn’t.”

Usually his investigations disprove a theory – of course a mysterious cabal doesn’t control the world – or expose craziness. It was rather different with this book.

Robert Hare, who came up with the industry-standard psychopath test, is a respected psychologist and what he was saying was undoubtedly true.

Psychopaths, defined as people who score highly on a list of traits including superficial charm, lack of remorse and failure to accept responsibility for their actions, really are everywhere.

At one point, Ronson even started to question if he was one of them.

Seeing a car wreck, he felt relieved that other people had already stopped to deal with it – did that mark him out as cold and unfeeling? Nearly crashing his own car due to the shock suggested not.

Once, Ronson said his adventures were a way of making sense of his own well-documented neuroses; this project only seems to have magnified them.

“I think I’m more anxious now than I’ve been in my entire life,” he says. “I’m a wreck. I have a constant knot in my chest. Right now, I have a groundless fear that people I’ve written about in the book will hate it. I genuinely get very worried about the possibility of upsetting people. I really want the people I write about to like the way they’re portrayed, even if I don’t like them.”

Is he some kind of masochist, I (half) joke? Isn’t investigating secret societies, fiercely held conspiracy theories and religious fanaticism the worst kind of work for someone prone to crippling anxiety? “It’s horrible,” he agrees. “There’s nothing better than when you do something safe – and you can do really good stories that are totally safe and noncontroversial.

It doesn’t have to be dangerous.”

The real worry, ironically, comes from being scrupulous.

“I feel a compulsion to examine a story from every angle and that’s where the trouble starts. That’s when you get into the nuance and grey areas and complexities.”

At least it defends him against any suggestions of sensationalism or exploitation.

His friend, the documentarymaker Adam Curtis, may liken Ronson to “a medieval monk, stitching together a tapestry of other people’s craziness”, but his work is a far cry from the TV crews who go off in search of the world’s fattest woman.

Like his contemporary Louis Theroux, he always attempts to take a more thoughtful approach. “In the past, Louis and I were probably quite competitive with each other but I think now he’s an example of one of the last good people still trying to do something intelligent. The bad ones take what Louis and I created and make freak shows.”

After all his years walking on the weird side, does Ronson sincerely believe anyone is actually “normal”?

He laughs. “I do see the craziness in people – a lot. I think I’ve always had this thing my whole life – I’ve never said this out loud before and it sounds a bit self-aggrandising – a sort of super-power, where I can talk to someone for a little while and understand what their troubles are, what drives them, where their insecurities come from, what they’re trying to hide.

“I think I’m quite good at reading other people and I think that’s probably what makes me a good journalist.

You meet the odd person who seems genuinely normal but there aren’t many out there.”

l Jon Ronson appears at the Pavilion Theatre, New Road, Brighton on May 26 as part of the Brighton Festival. The event has now sold out. For returns, call 01273 709709.

l The Psychopath Test is published by Picador and will be released on June 6, priced £16.99.