The reason that I think that rand gets sick, is because the land (world) is sick (so to speak).

 

The land is one with the Dragon and the Dragon one with the land.

 

So maybe the only thing that could cure the land could be the song that the Tinkers are searching for. Maybe thats the only thing that can fix the land and in turn fix rand. [/i]

Rand's sickness is a result of the mental connection that has formed between himself and Moridin resulting from their crossed balefire streams at the end of aCoS

Rand's sickness has been getting worse with his use of saidin, and LTT has been constantly in his head since the cleansing. Looks like he soaked up so much taint in that huge use that he is now (as Graendal said) insane (KoD near the end, "the voice in his head is a true voice, which makes it harder to reunite," or something like that).

 

"To live you must die," was an answer that Rand got from the doorway in Tear (the snake people), although he did not reveal that answer until much later. So what can cure Rand? Will he die at SG in TG, sealing the bore? If he dies, will he end up in Tel'aran'rhiod? Birgitte described memories of all her lives while in TAR but only each one life when in mortality. Does her physical extraction from TAR foreshadow a healed Rand/Dragon (or anyone else)? Birgitte sets an interesting precedent for Rand's injuries and insanity.

Luckers is right.

Rand has always been a bit sick after EOTW if you ask me