It’s that time of year again – when it’s acceptable to dress like a slasher victim, watch horror films until you’re confused about what’s reality and what’s fantasy, and basically get involved in anything that scares you shitless. Yes, it’s Halloween. And it’s no longer about kids wearing masks trick-or-treating door-to-door. Us adults want a piece of the action, too.

But what is it that draws us to such a macabre underworld? Why are we fascinated by the dark, the chilling and the psychologically disturbing?

Dr Brendan Walker, the world’s only ‘thrill engineer’, believes he has the answer. While in our everyday lives, most ‘normal’ people go to great lengths to avoid putting themselves in dangerous situations and being scared, there’s something inherently exciting about facing danger.

“It’s confronting your fears and surviving them which delivers this feeling of thrill, this euphoric rush,” Walker says. He explains that when we watch a horror movie, our bodies produce a chemical called cortisol – which usually happens when we’re stressed. But when the release comes – such as remembering a film is fictional or when a rollercoaster ride is over – we produce dopamine, which creates a “beautiful” sensation. A buzz.

“It’s the release,” Walker says. “It’s the sense of elation or happiness that produces dopamine which creates a sense of pleasure. The closest drug to this is cocaine, which creates the same sensation.

“It’s like an adrenaline rush, which is basically your body going into a high state of arousal. What you’re getting with a horror film are low levels of pleasure [throughout the movie], so the release and the reward can be much higher than, say, a rollercoaster [which delivers one big hit].”

However, just like drug addicts, horror fans are always looking for their next hit. “You’re constantly seeking novel things to get the rush, this payback,” Walker says.

If this sounds like you, you’ll have no problem sourcing your next hit in London. This Halloween, everyone wants a piece of the action – revellers can choose from the more light-hearted effort of clubs with amusing fancy dress themes to the more boundary-pushing, disturbing events, such as the screening of cult movie The Human Centipede. So if the thrill is similar to that achieved by taking drugs, does it mean peddlers of these events are similar to pushers?

Simon Drake, who lives in the House of Magic in central London, is quite happy to take that title.

“Metaphorically, my job is like a drug dealer – to get people in touch with their natural endorphins and adrenaline,” he says.

“People enjoy being frightened. The goriest part of my show is when I put an 18-inch knife through my arm with lots of blood. People laugh more than they scream. When people are frightened or horrified, they tend to laugh – so long as it’s not done in horrible taste.

“Having done horror for many years, it’s odd that people enjoy it, but they do. Horror movies are 90 minutes of quite cleverly calculated suspension and shock and people laugh because their body receives an injection of adrenaline. It’s a thrill, a rush, without taking drugs.”

– Carol Driver