Los Angeles (CNN) -- Amy Winehouse's death, a month after fans in Belgrade booed her from a stage for slurring and forgetting lyrics, raises questions about what could have prevented the tragedy.
While it will likely take weeks before toxicology tests reveal what killed her, Winehouse made it no secret that she had a substance abuse problem. She turned her defiance to rehab into her biggest hit song. "They tried to make me go to rehab, I said 'No, no, no,' " she sang.
Despite those lyrics, Winehouse sought help in rehab several times during the height of her career, often ahead of an important performance or a tour.
When she entered rehab in January 2008, her record label said it was "to continue her ongoing recovery from drug addiction and prepare for her planned appearance at the Grammy Awards."
Her last rehab stint was just two months ago. People magazine quoted a source close to the singer saying her father urged her to seek the treatment to keep excessive drinking from "becoming a bigger problem." The singer's representative told CNN at the time it was "to seek an assessment" before Winehouse began a summer tour of Europe.
That European tour was abruptly canceled after the first show, that disastrous Belgrade, Serbia, performance. She returned to London, but not to rehab.
Winehouse is the newest member of what is darkly known as the "Forever 27 Club," a list of music legends whose lives and careers ended at the age of 27. Janis Joplin, Jim Morrison, Jimi Hendrix and Kurt Cobain are headliners of the group, stars whose deaths could be linked to drug use.
Dr. Reef Karim, who runs the Control Center for Addiction in Beverly Hills, California, said it can be harder for celebrities to battle addiction for several reasons.
"They are allowed to continue to do their movies while in rehab, to go on tours before they are ready," he said. "So many people are relying on them for their income, their agents, their handlers, their entourage, their fellow musicians, and so many people want them to get better quickly."
Those "peripheral people" make it tougher to keep the musician on the prescribed treatment, Karim said. "We have to fight a lot of the handlers, the entourage, in order to get them the treatment they need."
They "jump back into the craziness and touring before they are ready and they are much more likely to relapse because of it."
Musicians sometimes believe they need drugs to perform and please fans, Karim said. He recounts what one rock star patient told him: "When I'm loaded or when I'm under the influence of something, people are really interested in me. When I'm sober it feels like nobody cares."
"Some people go through recovery and if they are producing great music, then great, but if they are not, the fear is that they'll disappear permanently," Karim said.
While true fans may care about the person, "the average fan may just care about what kind of things you are doing and how you make headlines," he said.
It may be easier for a celebrity to get noticed for a drug arrest, a drunken video or a trip to rehab than for a movie premiere. Every time Lindsay Lohan goes to court dozens of photographers line her path, yet her career is so stagnant her Screen Actors Guild insurance expired.
Lohan, who has spent eight months of the last four years in rehab, is having trouble paying for court-ordered psychiatric counseling, her lawyer told a judge last week. The judge agreed that Lohan needs the more expensive one-on-one help, not group sessions, which are cheaper.
Pax Prentiss, the CEO of the Passages Malibu rehab program, suggested that Winehouse's relapses into addiction were the result of a lack of one-on-one treatment.
"The treatment centers where she went to did not do individual therapies," Prentiss said. "They were group treatment facilities."
Prentiss said he was addicted to heroin, cocaine and alcohol for 10 years. "I was on death's bed for many years," overdosing several times, he said.
"I was at one time like Amy, going in and out of treatment centers, relapsing, sitting in group meetings," he said. His healing happened when he got the kind of individual treatment that he now provides at his facilities, Prentiss said.
Self-introspection is key to recovering from addiction, Karim said.
"A big part of recovery is looking at why you are so self-destructive and what it is about you," Karim said. "It's a spiritual disease as much as a social and biological disease. A big part of it is looking deeper at what's going on within you, how you feel about yourself."
Prentiss speculates that Winehouse was in "deep psychological pain, which is why she was abusing drugs and alcohol, and nobody had diagnosed that and worked on healing the deep emotional issues."
Her father, in a statement released after her funeral Tuesday, said his daughter "conquered her drug dependency" three years ago. She recently "was trying hard to deal with her drinking and had just completed three weeks of abstinence," he said.
"She said, 'Dad, I've had enough, I can't stand the look on your and the family's faces anymore,' " Mitch Winehouse said.
Addiction, Karim said, is hard for family members to understand. "You don't conquer this disease," he said. "You manage this disease."
Why would addiction suddenly take Winehouse's life if she was sober for three weeks?
"Addiction deaths are not only due to instant overdose," Karim said. "The toll that addiction takes on your body, on your immune system, the toll on the lack of absorption of vitamins and nutrients in your system, on your heart, liver, kidney" can lead to death over time.
Mitch Winehouse described his daughter as being "in good spirits" the day before she died.
"That night, she was in her room, playing drums and singing," he said. "As it was late, her security guard said to keep it quiet and she did. He heard her walking around for a while and when he went to check on her in the morning he thought she was asleep. He went back a few hours later, that was when he realized she was not breathing and called for help."
Pax Prentiss says he's "heard from different people who had a family member who died that they were doing great one day and the next they were dead."
"That makes a lot of sense to me," he said. "If she hadn't had a drink for three weeks, her tolerance went way down, and if she relapsed, a pill mixed with alcohol, she overdosed and died."
"I've seen that a lot with people," he said. "They go back to using the same amount of the drugs that they used before they were sober. Their system is not able to handle that same dose anymore."
Dr. Drew Pinsky, the addiction specialist who hosts HLN's "Dr. Drew" show and VH1's "Celebrity Rehab," agreed that several weeks of detoxification could have made Winehouse vulnerable to a drug overdose.