It wilL come as no major surprise to those who have read even one of his books that Patrick McGrath grew up amid and around the confines of a high-security psychiatric institution. From the age of five, the boy who would one day become the master contemporary chronicler of psychological disintegration lived close to Broadmoor Mental Hospital, in London, where his Irish-born father was Medical Superintendent.

The McGrath family were very much part of daily life within that institution. During the 1950s and 1960s, the administrative, security and therapeutic aspects of running such a hospital were less clearly defined. So it was that, throughout his childhood, Patrick found himself, alongside his parents, his sister and two brothers, attending drama productions and sports days and regular Sunday mass inside Broadmoor.

Women who had butchered their own children were permitted to ooh and aah over little Patrick. The quiet, inoffensive men who gave him jockey-backs and played football with him were multiple murderers, sadists and psychopaths.

Though he never knew specific details about the case histories of the patients with whom he sported and played, a deep fascination with mental illness and the mentally ill developed and became the central seam of his work as a writer.

“My father would never talk about the patients’ individual stories,” McGrath insists. “He hated that kind of prurience. After I was grown up and my father had retired, in later years, I’d ask him about someone and he’d say, ‘Oh, rape! Triple murder!’, and tell some terribly sad, bizarre tale of a life gone hopelessly wrong.”

Now aged 46, Patrick McGrath has spent over a decade and a half telling his own terribly sad, bizarre tales of lives gone hopelessly wrong. He came to fiction relatively late, around his 30th birthday, because he had spent his earlier years “trying to fulfil my father’s expectations of me being a socially useful citizen, finding a career in teaching or social work or something of that nature.”

Patrick worked for a while in a mental hospital in Ontario, Canada; first as a social work assistant and then research assistant to a psychologist. He enjoyed the interaction with the patients, and felt more comfortable with it than most, but knew that it would never be his life’s work. Further low-level professional jobs followed before he found himself in New York, at the beginning of the 1980s, working on his first collection of short stories, Blood And Water.

“At the back of my mind was always the thought that, ‘Wouldn’t it be grand to just go away and write?’,” he says. “But, for a long time, I thought that would be just too self-indulgent. I had this idea of being what my father would call ‘a useful citizen’. Then, gradually, I realised that I could become most useful as a writer. And, by now, I had some genuinely powerful and formative experiences to draw upon.”

McGrath’s initial work, such as the short stories and novels like The Grotesque and Spider, were macabre and ghoulish fantasies; alive with pickled limbs in jars, preserved brains hidden in attics and sinister smells wafting up from cellars. In more recent times, he has eschewed the grand gothic jokes for a more reserved and chilling style. These days, the horror in a Patrick McGrath book lurks in the mind, a much more terrifying locale than any abandoned graveyard or fetid crypt.

His most recent novel, Asylum, is his best yet, a gripping and impeccably-controlled yarn plotting the obsessive love affair between Edgar, an inmate of a hospital for the criminally insane, and Stella, the wife of a psychiatrist working there.

“I had heard a hint of a story like this many years ago in Broadmoor,” McGrath asserts. “But it was something that wasn’t discussed in front of the children. It lodged somewhere in the back of my mind. In the last couple of years, it began to niggle at me that here was a good story waiting to be told, the story of a psychiatrist’s wife who is guilty of some sort of impropriety with a patient. That was the seed.

“I think it’s a fascinating love triangle: a woman pulled one way by a husband who is a psychiatrist, pulled the other by a lover who is a mental patient. It allowed me then to examine other ideas. Such as having the story narrated by a psychiatrist who, at first, appears to be the most sane authority, a balanced, neutral, benevolent figure. But, bit by bit, he too appears to be misguided, blind and distorted in his view of things. Where does madness begin and end?”

Well, in so far as McGrath reaches a conclusion in Asylum, it seems to be that we are all essentially mad. And that, at best, sanity can only be measured on a sliding scale.

“Yes,” he concurs, “I’d say it’s a sliding scale rather than a Yes or No situation, rather than sanity and insanity being polar opposites. There’s a lot of grey area in the middle there. Stella’s story starts with her as a respectable, reasonably content, middle-class woman and winds up with her destroying her life and the lives of several others. But each of the steps that take her from here to there are ones that almost anybody might take in certain circumstances.

“She is a balanced person but that balance is destroyed. At any given moment, her judgement may have been a little off but you couldn’t say that she was mad. She became mad in small, incremental steps. That’s how it happens.

“There but for the grace of God go I. The mad are not pre-destined. It’s not as if a bolt of lightning comes and singles somebody out. It’s rather just bad circumstances, a bad decision, bad luck, and, suddenly, a life begins to unravel. I do not believe that one can be born evil or bad or mad. That damage isn’t there at birth. It is done by the world and by circumstances.”

The idea that creativity is simply another name for madness is another strong theme in Asylum. “Yeaaah,” smiles McGrath. “Most creative people have only a very fragile protection around a very childlike core. Creative people often spend a lot of time basically working by themselves. It’s the way the job works. You miss out on all that stuff that goes on in the world every day, where people get a lot of affirmation from each other. You don’t have your own worth and your view of reality reinforced.

“Those small interactions are very important. If you’re not out in the world and particularly if you’re engaged in work of the imagination – painting, drama, songwriting, fiction – you can lose touch and become heavily dependent on your partner. That’s where you’re getting your society, your contact with other people, your reflection of yourself. That can make for a certain fragility. It can certainly make for a strained relationship with your partner, if you have one.”

What’s Patrick McGrath’s opinion of the mental health of the writers he knows?

“They’re probably all within normal limits,” he avers. “They can be a bit excessive in their indulgences. There is something I don’t like about writers and that’s their level of competitiveness. It gets very unhealthy, to the extent that we often set ourselves up as people who are not getting our due. There is a certain bitterness that creeps in, a bitter response to the world and to other writers that is very destructive. I’ve seen that, and that’s not very healthy mentally.”

In terms of the future, Patrick McGrath doubts if he will ever write about anything else but the meagre membranes that separate sanity and insanity, the so-called sane and the so-called insane.

“I’m very happy to spend the next 30 years working through the different species of madness,” he grins. “It takes a very sure sense of your own identity and your grasp of reality to remain at all times very clear about what’s appropriate, what’s inappropriate, what’s sane, what’s insane, what’s disturbed, what’s normal. Understanding what the boundaries of the normal are is quite difficult.

“I’m intrigued by forms of madness. There are so many ways that we find of adapting to the world, adapting to reality. We all have our quirks and curious ways of making those adjustments.

“I’m very alert to those people for whom that adaptation becomes bizarre or in some way extreme. Forms of abnormal psychology are what get me going. Maybe that tells you something about my own abnormal psychology.” n

• Asylum is published by Viking at £16.