Michael Jackson was allegedly an "emotionally paralysed mess" in the weeks leading up to his death.
The singer died in 2009 shortly before he was due to return to the stage with his This Is It shows in London.
The Los Angeles Times has obtained a series of emails sent by those involved with the event.
Michael apparently missed rehearsals, struggled to learn dance routines and refused to sing at practices.
Concert promoter AEG’s Randy Phillips reportedly sent several emails to AEG President Tim Leiweke expressing his fears for the comeback concerts.
Phillips brands Michael "an emotionally paralysed mess," and claimed the star was "scared to death."
"MJ is locked in his room drunk and despondent ... I [am] trying to sober him up," he revealed in an email before the 2009 press conference where Michael announced the live shows.
The show’s director Kenny Ortega apparently requested professional help for Michael after concerns for his health grew.
“There are strong signs of paranoia, anxiety and obsessive-like behaviour. I think the very best thing we can do is get a top psychiatrist in to evaluate him ASAP,” he wrote in one email.
“It is like there are two people there. One trying to hold on to what he was and still can be and not wanting us to quit him, the other in this weakened and troubled state.
“MJ is not in shape enough yet to sing this stuff live and dance at the same time,” Kenny wrote in another email.
AEG is currently in a legal battle with insurance firm Lloyds over whether the brokers should pay out £15 million for Michael’s failure to perform at the shows.
Lloyds are attempting to nullify their policy with AEG as they allege false claims were made about Michael’s health.
Michael’s family has accused AEG of forcing the star to carry on with the comeback shows.