This song takes Adam Young, who records under the moniker of Owl City, into new, rockier territory. It features Mark Hoppus, the lead singer from Blink-182, who provided bass and co-writing to the track. Hoppus also contributed vocals to the second verse and accompanied Young on the chorus. The Fireflies singer told Billboard magazine that working with Hoppus, "was a privilege and an honor." He added, "I've always been a big blink fan, so to have him sing on the track, I still play it back and can't believe it's Mark on the track. It's awesome."
The song documents some of the more psychotic thoughts and feelings Young dealt with in the wake of his successful Ocean Eyes debut album.
The experience of working with Hoppus lived up to everything Young had imagined, and then some. "I learned [from working with him] that it is possible to be at a level where Mark is at and still be incredibly genuine and incredibly real," he told MTV News. "Because, first of all, I've never laughed so hard in the session 'cause the guy's so funny and he's always like, he's like the funny guy who's in that band and he just has this thing where it's so him and sometimes you meet people and you're not sure if they're really the way they perceive themselves to be," he continued. "But it was so cool and I've been such a nerdy Blink fan forever. I was like 'There he is. He's in the studio and he's singing on my song. I can't believe it.' Totally [a] dream come true, it was awesome."
The track does pay homage to Hoppus' band. "It's definitely Blink-influenced," Young told MTV News. "I've been such a fan of what they do, what Blink's done since junior high. I'll have the CD on in the car, just randomly trying to memorize the lyrics, and that song will come on and I'm like, 'Oh, that's Mark Hoppus.' It sounds like an older B-side, rarity Blink track. It's so cool. It's such an honor."
Young told AOL Music that the track was inspired by the consequences of wallowing in regret. "It's a darker song about how everybody thinks of how life would be different now if you had made better choices in the past," he explained. "If you let it, that can drive you crazy. If you don't let the past stay in the past, it'll be worse. It's hard to know in the moment how the choices I'm making right now will affect me later, but you can't really think about that."
"'Dementia' is my way of saying let the past stay in the past," added the Minnesota musician. "Don't let the 'What ifs' frequent your mind too much. Put that stuff to bed."