The films that find their way under our skin in the most enduring ways are usually psychological thrillers. You know the ones­ – movies like The Sixth Sense, What Lies Beneath, The Shining and those trusted Alfred Hitchcock classics – films we simultaneously can’t look away from but almost can’t bear to watch. They mess with our heads in the best possible way, leaving us wondering why we do this to ourselves long after the credits have finished rolling.

But why do they work so well? What makes a thriller a thriller, and why are we always here for it, even if we were actually really freaked out last time? Auteurs of the genre have developed a tried-and-tested formula to keep audiences coming back for more. In advance of the highly anticipated release of Steven Soderbergh’s Unsane, we’ve rounded up what you’ll see in every great and mind-melting psychological thriller.

*Mild spoilers ahead*

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It’s All In The Mind

Unlike slasher or monster flicks (which, incidentally, can sometimes go hard with the cheese), the ‘big bad’ inherent to psychological thrillers is usually immaterial, pared back and intrinsically linked to the psychology of the protagonist.

This works to make these films creepy AF, because it’s really hard to know what’s real and what’s the product of a clinically deranged, overactive imagination. Are those creepy twins lurking in the corridors of The Overlook Hotel actually out for blood, or are they fragments of a fever dream cooked up by a pent-up, murderous writer? In any case – which is worse?

The pay off at the end of a psychological thriller comes in the form of a protagonist defeating his, her, or its inner demons, or overcoming some sort of personal struggle.

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We Don’t Know Who To Trust

 In forthcoming psychological thriller Unsane, we’re introduced to Sawyer Valentini (played by Claire Foy), a young woman seeking therapy after a particularly harrowing experience with a stalker. She inadvertently checks herself into a treatment facility and, if you ask her, is being kept there against her will.

There’s just one problem: we’re not sure who to believe – Sawyer, or the facility personnel who’re all claiming she’s lost her mind and needs rehabilitation.

So sets up a classic psychological thriller trope ­– that of an unreliable narrator. The story in psychological thrillers usually unfolds from the perspective of a protagonist (or an antagonist), but how can we be sure that said protagonist isn’t criminally insane, lying to wriggle their way out of punishment? The joy in these films lies in searching for clues or signposts, even though most directors will choose to keep them well hidden.

In some cases, it’s fun to play along – the mischievous, charismatic soap salesman Tyler Durden was only ever a figment of the narrator’s imagination in Fight Club (the name of Edward Norton’s character is never revealed in the film), but he was still thoroughly entertaining nonetheless. As it turns out, the narrator suffers from dissociative identity disorder.

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Just When You’ve Got It All Figured Out…

Surprise! Everything you thought you knew about this film has just been completely turned on its head by a brilliantly crafted plot twist that plays out in the final 10 minutes. Plot twists are arguably what makes psychological thrillers so addictive – no matter how hard you look for them, you never see them coming (anyone who says they knew Bruce Willis was dead before the reveal at the end of The Sixth Sense is lying and should get in the bin).

But come they will. And yes, you will invariably re-watch the entire film once the Big Twist is revealed, if only to hunt for clues.

M. Night Shyamalan is arguably the master of plot twists, with The Village, The Sixth Sense and The Visit to his credit. We’re hanging out for the twist at the end of Unsane, though – we’re betting on the whole psy-thri genre that it’ll be a doozy.

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Smart Scares

Psychological thrillers are less about jump scares, and more about fostering an impending feeling of dread accompanied by goose bumps and chills. When Natalie Portman starts pulling her cuticles off in Darren Aronofsky’s 2010 film Black Swan, we’re mortified rather than scared – we feel it in our own fingers. Similarly, when Sawyer’s stalker keeps re-appearing in Unsane, even though she’s moved cities to get away from him, we’re not so much scared for her physical wellbeing (because how can he be there, really?) as we are for her mental health.

Directors of psychological thrillers use scares sparingly and ingeniously, to ensure audiences are questioning what’s real at every turn.

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It Might Seem Like Ghosts Are To Blame, But They Probably Aren’t

Many psychological thrillers delve into the world of the supernatural – in What Lies Beneath, Michelle Pfeiffer has to face up to a (dead) woman scorned; in the truly harrowing New England folktale The Witch, a pilgrim family is quite literally torn apart by suspicions of witchcraft.

The genre handles the paranormal deftly (read: in a way that makes an audience want to collectively shield eyes and block ears), but here’s a fun fact: the supernatural elements are almost always metaphors for real-life challenges faced by our protagonists. Michelle’s real problem in What Lies Beneath is her ratbag husband, played by Harrison Ford. In The Babadook, the issue is not a spooky, hairy book monster after all, but problems arising as a result of unresolved mental health problems.

Still, though – it could be ghosts.

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(Lead image: Unsane/20th Century Fox)

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Don’t miss the heart-pounding new psychological thriller from Steven Soderbergh, Unsane. In cinemas April 25.