The 'Candy' hitmaker - who has done two stints in rehab himself - is concerned for the wellbeing of the 20-year-old singer and is worried the staggering level of fame she has achieved could have a negative effect on her.
He said: ''Miley's got the world talking and looking at her. And the spotlight that's now upon her is rehab-making. It has a detrimental effect on your psyche. I've had a similar light shine on my direction and it f***s you up - for a long time.''
The 39-year-old star believes the 'Wrecking Ball' hitmaker - who shot to fame on Disney TV show 'Hannah Montana' - is fighting against the showbiz industry and trying to break away from her father Billy Ray Cyrus.
He explained: ''She's just a kid. She's a kid who looks as though she's rebelling against her father and rebelling against the industry that put her in a Hannah Montana-shaped box.''
Miley has caused controversy in recent months following her raunchy performance with Robin Thicke at the MTV Video Music Awards in August, and lighting what appeared to be a marijuana joint at the MTV Europe Music Awards at the weekend.
However, Robbie believes Miley is merely struggling to deal with being so famous and blames her wild behaviour on her child stardom.
Speaking to the Daily Mirror newspaper, he said: ''She makes good pop records, she's got a nice body and a beautiful face. She's a good pop star. But that spotlight is too intense even for the most well-rounded people. They'd find it impossible to deal with, let alone someone who's been a child star since they were three or whatever.''
The novel's author saw a cut of the film and loved each of the changes the movie's director had made.