The Oscar-winning actor stars opposite Denzel Washington in the film, which tells the story of Leto's Albert Sparma, who is being investigated by Denzel's Joe 'Deke' Deacon. But getting into the right mindset to play a killer took its toll on Leto.
"You're spending time in a dark place, and the materials, the research can start to creep into your dreams at some point," he told Entertainment Tonight. "For anybody, that's, like, binge-watched Making a Murderer, at a certain point you need a break. You need to turn on Tiger King or something."
But while there were some difficulties in taking on the role, Leto was determined not to let the opportunity of working with Washington pass him by.
"I don't know what it is about him in particular that I keyed into as a young actor, but I always wanted to see what he was going to do next," he added. "He's always great. He always surprises you. He's one of the few actors that has really had that consistency, and he really puts his full body and heart and soul into every performance that he does. So, just the Denzel of it all was enough reward for me."
Jared Leto was last seen on the big screen in 2018's "The Outsider". He will next be seen reprising his role as Joker in "Zack Snyder's Justice League". His other new projects include true-story movie "House of Gucci" and Marvel superhero adaptation "Morbius".