Leigh also reportedly drew inspiration from his own experiences with sleep paralysis as well as his active interest in astral projection. He came up with the basic idea for Insidious several years before it was made, but he and James put it on the back burner and didn't do anything with the story until the time was right.
"When we were trying to come up with another film to do together, I went back to that idea [of astral projection], and it kind of just struck me as something I hadn't seen before," Leigh told SciFiNow in 2018. "I basically wanted to see the world from a ghost's perspective – like, what does the plane that ghosts live on look like?"
Article continues below advertisement
The writer continued, "If you think about a haunted house movie, the ghosts or spirits that appear in the house appear and disappear, they're not just sitting in the corner drinking tea and hanging out, they're not raiding the cupboard for snacks, they're there, and then they're not there."
"So that made me think that they exist on some other plane," he added. "It's the same dimensional space, they're still in your house, but it's a different version of your house, and that's what led to the Further."
