LOST Finale Question...?

In Lost did everyone die in the plane crash and was the whole thing all in Jack's head? I personally do not believe that but it seems to be a pretty reasonable idea, looking back on the end of the finale and the start of the pilot. It starts with Jack opening his eyes in the bamboo forest and ends with him closing his eyes in the bamboo forest. It seems that for that theory to be true there would have to be a lot of red herrings and irrelevant info. Have the creators, directors, producers, etc released any type of statement on what the finale meant?