Sydney - Swimming great Ian Thorpe was in rehab for clinical depression on Tuesday after a mixture of painkillers and anti-depressants left him disoriented on a Sydney street, his manager said.
But James Erskine insisted no alcohol was involved, as the swimmer's father expressed confidence that his son would "come out the other side".
A "dazed" Thorpe, 31, was discovered by police attempting to get into a car near to his parent's house in the early hours of Monday and taken to hospital for assessment.
It was his second recent visit to hospital, after falling and needing shoulder surgery last week. At the time, his management denied reports that he was also being treated for depression and alcohol abuse.
Erskine told the Australian Broadcasting Corporation that the five-time Olympic gold medallist was now receiving treatment for depression, a condition Thorpe has struggled with for years.
"He'd been taking prescribed drugs, painkillers for his shoulder and he's also on prescription drugs for anti-depression... but it's obviously a mixture of it and that mixture made him disorientated because he was wandering around at 3 o'clock in the morning," he said.
Residents rang police after Thorpe tried to get into a car that he thought belonged to a friend.
"He became disorientated and he tried to get into what he thought was a friend's car, but it wasn't his friend's car at all," Erskine said.
"The police came; they were fantastic, they realised it was Ian Thorpe and they called an ambulance."
As well as being open about his depression, Thorpe detailed a battle with alcohol in his 2012 autobiography, but Erskine said it was not a factor in Monday's incident.
"There was no alcohol involved, he hadn't been drinking or anything like that," he said.
"The hospital then suggested - or more than suggested, I think - that he should go into rehab for depression and that's what's happened."
Thorpe's father Ken told the Sydney Daily Telegraph he hoped his son would pull through.
"He is battling with his health issues at the moment and he is having a tough time," Ken Thorpe said, reportedly choking back tears.
"But hopefully in six months' time he will be out the other side."
Thorpe is Australia's most decorated Olympian with five gold medals at the 2000 Sydney and 2004 Athens Games, with his extraordinary success attributed partly to his abnormally large feet and hands.
He became the first person to win six gold medals at one world championships, in 2001, among 11 world titles overall - along with 10 Commonwealth Games gold medals.
But the demands of a celebrity lifestyle and grinding training sat uncomfortably with Thorpe and he quit in 2006, dabbling in jewellery design and television after his retirement, before a comeback when he failed qualify for the 2012 London Olympics.