Everyone has a horror film they saw too young. Or perhaps just one disturbing scene that made them too jittery to sleep at night. A set of dining chairs stacking themselves into a table-top pyramid as a housewife’s back is turned. A woman’s discovery of a neighbour’s slumped corpse, his eyes pecked to bloody sockets by murderous birds. A boy on a tricycle seeing twin girls at the end of a corridor, interspersed with flashes of their brutal axe murder …

I started watching horror back in the early 80s, when I was five. A mature student, my dad would record late-night Open University lectures on BBC Two, and, once the bearded academics finished scribbling equations on blackboards, the Betamax kept rolling and the melodramatic titles for a Hammer horror would start up. From these tapes I remember hopping plagues of alien locusts from Quatermass and the Pit, Christopher Lee baring his blood-soaked fangs, and young women in Victorian nightgowns, screaming and fleeing or becoming mesmerised. As a five-year-old, could I differentiate between these supernatural fictions and reality? I saw a chiller called The Watcher in the Woods and began to creepily insist that “the Watcher” was stalking our family, following at a distance, lurking just out of sight. This coincided with the time my parents were separating, and the Watcher now seems to me the exteriorisation of some inner anxiety and sense of threat to the family unit. These films were “just pretend”, I’d been told. But even at a young age the Hammer productions seemed to express to me a fundamental truth: that just beyond the edges of what is safe and known are destabilising forces that can throw everything into chaos.

My best friend at primary school saw A Nightmare on Elm Street when we were seven. We gathered around her in the playground to hear about Freddy Krueger slaughtering teenagers in their dreams. I begged permission to watch it too, but, frustratingly, had to wait until I was “a bit older”, which turned out to be 10. How many hours of sleep did I lose to imagining Krueger leering around my bedroom door? The long blades attached to his leather glove tapping on the windowpane? Thanks to lenient parenting, secondary-school sleepovers often featured Puppet Master, Child’s Play and other video nasties whose power wasn’t diminished by their low-budget awfulness. Nor did the regular exposure desensitise me; it only made the monsters more persistent in my consciousness. Then I got into Stephen King novels, which were no reprieve. I was often awake until 2am with a spine-cracked paperback of Pet Sematary or It, too scared to go to the toilet, in case Pennywise was waiting to pounce down the hall.

Have I mentioned yet, that this was exhilarating? Fun? It’s what film theorist Noël Carroll calls the “paradox of horror” – the enjoyment of fear and disgust, the thrilling of the sensation-seeking parts of the psyche as we vicariously experience horrifying situations and confrontations with entities both evil and grotesque.

And there are none more evil and grotesque than Pipes of the infamous Ghostwatch, which I saw with my younger sister when it was broadcast on Halloween 1992. Like most of the audience of 11 million, we fell for the mockumentary hoax, and, like approximately 1 million viewers, we called the phone lines to tell the BBC we’d spotted the ghoulish Pipes fleetingly in shot, in the corner of a bedroom. Too petrified to go to bed, we stayed up until dawn, under a duvet on the sofa, watching the Halloween programming on BBC Two – Creepshow 2, The Curse of the Werewolf, The Bride of Frankenstein, Death Line – until exhaustion finally overrode our fear.

As well as its ingenuity and authentic script, maybe another reason Ghostwatch was so real to us was because the setting was so close to home: the London suburb, the frazzled working-class single mother, the two highly strung adolescent daughters. I’ve always had the irrational sense that my Essex childhood home is a haunted place. It’s familiar at the level of nook and cranny yet can sometimes be unheimlich and strange. If the house is haunted, perhaps it’s by ghosts of our former selves: by second-generation teenagers clashing explosively with the first generation’s authoritarian parenting style.

Recently, I came across the word “transliminal” to describe someone swayed by the supernatural. People high in transliminality tend to be introspective and fantasy-prone – the boundaries between the mental and the external world more porous, so the imaginary has a stronger grip on “reality” and emotional states. The way terrifying scenes lingered in my mind and contaminated my post-film reality when I was younger suggest this trait in me. It suggests why, as a teenager, rain tapping my windowpane in the night became Danny Glick from Salem’s Lot, hovering vampirishly outside. Why bin bags heaped in an alleyway, glimpsed walking home from a late-night screening of Scream, became the masked slasher, crouched with a 10in knife. The psychological disturbance of a film used to stay with me, rippling out into subsequent days, filling my head with imaginings of the Blair Witch or the serial killer from The Poughkeepsie Tapes, creeping about my flat at 3am. Ridiculous, my rational mind scolds. But on some more visceral, irrational level, I am spooked. And I enjoy being spooked. It’s part of the draw of the genre for me. Fear heightening my senses, so I am hypervigilant and alert. Fear waking me up.

Since I began writing 23 years ago, my fiction has always contained elements of the supernatural, and my latest novel, Old Soul, is an out-and-out horror: my monstrous female protagonist must make human sacrifices or she literally begins to rot. Her internal organs putrefy. Her hair falls out. Her fingernails falls off. She becomes the walking undead – all my fears of evil, ageing and mortality, rolled into one.

My north star while writing Old Soul was to make readers feel the way I did when first turning the pages of The Shining or Mark Z Danielewski’s House of Leaves: frightened, disturbed and utterly beguiled. The experience of reading horror is vastly different from watching a film. Books can’t do jump scares the way films and TV can. But they are more adept at inhabiting a character’s interiority – their fear and confusion as they mentally scramble to make sense of the door slamming in the night or the shadow flitting down the hall. A horror novel is a collaboration between author and reader; the words on the page are stage directions for the reader’s imagination. The monsters are unique to every reader, too, constructed in part from your own mental archive of terrifying images and experiences.

The horror I saw too young definitely had some warping influence on my growing mind. For me, the genre will always represent the disintegration of the safe, known world: the threats that lurk at its periphery metamorphosed into the poltergeist smashing vases in a suburban home, the witch cackling in the woods, the demon-possessed little girl … Horror became linked to unhappy events in my life, a grotesquely distorting mirror held up to my childhood, somehow reflecting a greater truth. But this is by no means a wholly bad thing. In fact, I feel a strange kind of gratitude for all I was exposed to at an early age. For, amid the heart-thudding terror, I’ve been comforted, too, by horror’s metaphorical powers, and the dark recognition of all the ordinary horrors in an ordinary life.