Elizabeth Olsen and Sarah Paulson star as sisters. Credits: Fox Searchlight Pictures

In a Reddit thread titled ‘What’s the most horrific movie you have seen that’s not billed as a horror?’, someone said: “Martha Marcy May Marlene (2011). I watched it last week and can’t stop thinking about it.”

They added that the movie was ‘deeply unsettling’.

Echoing similar sentiments, another person penned: “MMMM haunts me to this day. There is something so bleakly terrifying and twisted about that one. The vibe makes me feel so off.”

Martha Marcy May Marlene trailerCredits: Fox Searchlight Pictures0 seconds of 2 minutes, 31 secondsVolume 90%

“Yeah, that ending,” another Redditor replied.

“And even the way her family clearly don’t understand what she’s been through, so it just feels so hopeless.”

“MMMM has this quiet tension… very unsettling,” someone else added.

Martha Marcy May Marlene boasts an all-star cast made up of Marvel star Elizabeth Olsen, Sarah Paulson, Hugh Dancy and Ozark favorite Julia Garner.

The synopsis for the R-rated movie reads: “After several years of living with a cult, Martha (Elizabeth Olsen) finally escapes and calls her estranged sister, Lucy (Sarah Paulson), for help.

“Martha finds herself at the quiet Connecticut home Lucy shares with her new husband, Ted (Hugh Dancy), but the memories of what she experienced in the cult make peace hard to find.

‘Not even a horror’ movie leaving viewers ‘messed up’

“As flashbacks continue to torment her, Martha fails to shake a terrible sense of dread, especially in regard to the cult’s manipulative leader (John Hawkes).”

The film is described as ‘unsettling’. Credits: Fox Searchlight Pictures

The movie was made on a tiny $600,000 budget and went on to make $4.7m at the global box office.

It’s widely credited as Elizabeth Olsen’s breakthrough role, before she went on to play Wanda Maximoff/Scarlet Witch in the MCU.

Cult deprogrammer Rick Alan Ross has even dubbed the film the ‘gold standard for any movie about cults’ in an interview with Vanity Fair.

He said: “It is the most realistic depiction of what a cult would be like and the difficult of leaving the group and the recovery process.

“She feels, like many cult members, that thinking of leaving is being a traitor.”