According to one onlooker, she was "totally out of it". When Lindsay Lohan turned up at a Golden Globes after-party held by Prince last week, the actress, who attends Alcoholics Anonymous meetings, was apparently so much the worse for wear that she grabbed a stranger and asked: "Can you help me find my friends? I can't find my friends." Two days later she checked into rehab.
Hardly a week goes by without a celebrity playing out their addiction in public or indulging us with their tale of recovery. Pick up a paper or turn on the television and it's likely that you will come across a star who has come a cropper at some stage.
Kate Moss is now officially Cocaine Kate. Kerry Katona's recent autobiography recounts her stays in the Priory for drug and drink problems, as well as in an Arizona rehab centre. And many people know more about Pete Doherty's addiction to drugs than his music. They follow in a long line of stars who have caved in to temptation: Elizabeth Taylor, Liza Minnelli, Melanie Griffith, Johnny Cash, Gazza, Michael Jackson, Naomi Campbell, Davina McCall, Elvis, George Best, Paula Yates...
So, what is it about celebrities that makes them apparently so prone to addiction? Dr Alastair Ross, a psychologist at the University of Strathclyde, believes that part of the answer may lie in personality type. "A neurotic or extrovert is more likely to become an entertainer or someone in the public eye. That might underpin certain types of addictive or compulsive behaviours," he says.
People who become actors and musicians tend to be extrinsically motivated, and their sense of self is bound up in what others think of them. It results in emotional highs and lows, and often depression. "If you are needy in that sense, you can become obsessed with your press cuttings, obsessed with what the critics and fans think of you," Ross adds. "As soon as the critics start turning on you, which happens to all artists at some point, you're on an emotional roller-coaster."
Another factor is the environment celebrities find themselves in, as it encourages excess. "I played in a band for years and we didn't have any money, but we always had drink," Ross says. "Everywhere we went there would be a free bar. The drink was the first thing that was laid on. Maybe you wanted a cup of tea, but that wasn't really an option."
Stars are also expected to act in a certain way, leading the charge towards the free bar and partying hard. On the road, they are often cut off from the stabilising effect of friends and family. "People who live in poverty, specially in inner cities, can get in a mess with drugs. Celebrities suffer a different kind of poverty, a poverty of meaningful relationships," Ross says. "People you have known for a long time will tell you that you look stupid. Nobody would ever tell most of the celebrities that they look stupid. That's why they sometimes leave the house looking ridiculous, because most people will always tell them that they're great."
Celebrities can often be surrounded by people who collude in their addiction, says Dr Michael Scott, medical director of Sierra Tucson, a treatment centre in Arizona. The clinic, which specialises in addiction, is known for its celebrity clients, who have included Ringo Starr, Rob Lowe and Michael Douglas.
"Celebrities are, directly or indirectly, supporting a number of people, such as their agent and everybody else they work with," Scott says. "These people have a real vested interest in how well the star does, and they tend to keep things quiet when they shouldn't. It's out and out enabling. If the celebrity gets help it could compromise their own job and they don't want that to happen. They tend to be one of the major obstacles. They can also be a major asset, but they often are a major obstacle."
Addiction for "civilians", as Liz Hurley charmingly referred to non-celebrities, still carries an enormous stigma. People struggle to hide their drinking and drug habits out of fear that they may lose their jobs. With celebrities, not only is addiction widely tolerated, but admitting to a destructive habit can jump-start a failing career in terms of sympathy and press coverage. It's a subject that can guarantee a place on a chat-show sofa and a huge book-deal from a publisher.
"I'm sure the marketing people will tell you that it sells as much as any other press," Ross says. "The evidence of that is the bandwagon-jumping. As soon as somebody goes into rehab, suddenly you see a dozen people coming out with their own rehab stories."
The psychologist doubts that all the stars telling such tales have actually had a medical diagnosis. "I do think that there is a social and cultural threshold now, which is quite low, whereby you can just say you're addicted to something for functional reasons, usually to get yourself off the hook if you've done something bad.
"If celebrities do something that is socially unacceptable - for example, with respect to sexual behaviour - they will often claim to be addicted. Michael Douglas seemed to be just another guy who cheated on his partner. But he had access to good lawyers and good PR, and the explanation that he was addicted emerged and he was going to get help and people felt sorry for him.
"I think Kate Moss had to originally come out and say she had a problem with cocaine for PR reasons. I wouldn't know whether there was a clinical problem, or whether it was just recreational drug use and the main problem was that she got caught," Ross says.
Being a celebrity can cause problems during treatment. "It's very hard for a public figure to get better when they are in the public eye," Scott says. "In group therapy sessions they are afraid that it will leak, which it often does, or they are embarrassed to say it in front of their fans.
"In order to get better these people often have to bare their souls, and it takes a very trusting environment to be able to do that. That's why we are fortunate, because we are able to maintain confidentiality pretty well. But at times it's very difficult. We put a lot of faith in the patients. We address the importance of confidentiality all the time and stress that their personal recovery depends on the confidentiality of everyone there. They quickly take it to heart."
Celebrities are treated like everyone else and have to attend group therapy sessions at the clinic. "They have to be treated the same because we are treating the person and no matter what job they are in, that's what they do," Scott says. "Part of recovery is to address who they are and it's often hidden in layer on layer of external garb."
'Since the 1990s, there's nothing you do as a pop star that no one else does. A hedonistic lifestyle... is totally normal' - Mike Skinner
'I don't let booze and drugs around me now. I don't want to go down that road again' - Robbie Williams
'I used to try to control my moods with drink and drugs' - Sophie Anderton
'I was living in a world where I could have what I wanted without constraint. The damage to my nose was just the outer manifestation of what was going on inside' - Tara Palmer-Tomkinson
'When I'm angry, I miss being able to switch off. When there was a build-up of nonsense, it was just so comforting to know I had a couple of bags of heroin' - Russell Brand
'When I was an addict, I just let everybody down and maybe because I did have strong morals and good manners and stuff, that made me hate myself' - Davina McCall
'Drink and drugs provided a mask for me to hide behind. They meant I could pretend to be the bubbly Kerry everyone loved' - Kerry Katona
'The first victory was against alcohol. The second was against drugs. The third was just for me' - Paul Gascoigne