By Bad Seed
Nobody for sure knows what this song is about but that is how Kurt would have wanted it. But here are some guesses/facts/reviews about "Downer" from songfacts.com :
This was Kurt Cobain's attempt at a political song. In the song, Cobain laments on nuclear war, radicals who believe the world is going to end, and other issues. Said Kurt: "I was trying to be Mr. Black Flag Punk-rock guy... I didn't know what I was talking about."
This song was included on Nirvana's album Incesticide after it's release on Bleach because it was a song Nirvana rarely played live and Kurt Cobain wanted people to hear it.