Excerpt from Rolling Stone’s 2000 interview, Blink-182: The Half-Naked Truth:

Hoppus and [Skye] Everly have been together for about a year; before that, he was unhappily single. “Adam’s Song,” Blink’s current single, is a suicide note set to music, but Hoppus says he wrote it about being lonely on tour. The couplet “I couldn’t wait till I got home/To pass the time in my room alone” originally ended “to get off the plane alone.”

“Tom and Travis always had girlfriends waiting back home, so they had something to look forward to at the end of the tour,” Hoppus explains. “But I didn’t, so I was lonely on tour. But then I got home and it didn’t matter, because there was nothing there for me anyway.”

It has been falsely rumoured that the song is actually inspired by fictional character, Adam Krieger’s suicide note. The following is from one the band’s tour programs' description of the song:

The story behind that is Mark read a letter someone sent him as an email, that a kid wrote before he committed suicide to his parents. We kind of got together and wrote this sad, slow song. It came out sadder than we ever thought it would, which is good too. Any song that moves you is good. Some people listen to it and go ‘Wow, that’s a real bum-out of a song.’ But it’s one of those things, a story of a kid not being happy in his life, crossed with us being really lonely on tour. At the end of it there’s a better way out, there are better things to do than kill yourself.

The character of Krieger is from a play called “Adam’s Letter”. The full note has been posted to Tumblr.