The A24 film follows Pugh’s character Dani on a trip to Sweden to attend a midsummer festival with her increasingly distant boyfriend Christian (Jack Reynor) and his friends.
At the end of the movie, Dani is crowned the May Queen and chooses to sacrifice Christian after a slew of disturbing events.
Speaking on the latest episode of the Off Menu podcast hosted by comedians James Acaster and Ed Gamble, Pugh said she struggled to shake the character off and even felt guilty for leaving her behind.
“When I did it, I was so wrapped up in her,” Pugh said. “I’d never played someone that was in that much pain before and I would put myself in really s*** situations that maybe other actors don’t need to do but I would just be imagining the worst things.”
She continued: “Because each day the content would be getting more weird and harder to do, I was putting things in my head that were getting worse and more bleak.
“I think by the end I definitely abused my own self in order to get that performance.”
The 27-year-old said that when she left the shoot to go and film Greta Gerwig’s Little Women (2019) in Boston, she felt remorse for the tragic character she’d created.
“I remember looking [out the plane] and feeling immense guilt because I felt like I’d left her in that field in that state,” she said.
“Obviously, that’s probably a psychological thing where I felt immense guilt of what I’d put myself through but I definitely felt like I’d left her there in that field to be abused… almost like I’d created this person and then I just left her there to go and do another movie.”
Pugh has previously spoken about feeling “raw” and “exhausted” after the film’s lengthy crying scene with other women from the Harga commune.
“By the end [of the scene], we were all in each other’s laps and crying and allowing our bodies to keep heaving,” the actor wrote on Instagram.
In a four-star review for The Independent, critic Clarisse Loughrey called Midsommar “one of the year’s strangest, most distressing, and most memorable films”.
Aster’s new film, Beau is Afraid, starring Joaquin Phoenix, is scheduled to release in cinemas on 21 April this year.