The song's meaning is basically about obsession and addiction, but not in a creepy way (although, let's be real, it can be a little unsettling at times). It's more like, have you ever been so into someone or something that you can't think straight? Yeah, that's what this song is about. Intense longing and desperation are the main themes here.
R Thom Yorke, the lead singer, has said that the song is about the compulsion to be with someone, even if it's toxic or unhealthy. It's like, you know when you're in a relationship and you're all "I need you, I need you, I NEED YOU"? Yeah, this song is like that, but on steroids. And, let's be honest, who hasn't been there at some point, right?
