Kelly Osbourne has blamed her DNA for her addiction.
The presenter - whose father, rocker Ozzy Osbourne, has had a long-running battle with drugs and alcohol - believes her dependence on prescription drugs is something hardwired into her genes.
Kelly - who is now drug free - told Britain’s BBC Radio 5 Live: “I don’t have any shadow of a doubt that addiction is a disease. It is in your genes.
“The only people in my family who don’t have that gene are my mother and my sister Amy. I consider myself lucky that I saw both sides of it. Drugs stop you from screaming on the outside, but you are still screaming on the inside.
“I was addicted by 16. Drugs stopped me from feeling a certain way. Some people experience euphoria but I never felt that. They numbed me and gave me confidence. It was like a magic medicine.”
Kelly - who has been in rehab four times, most recently in January - admits she became a recluse during her lowest points of addiction.
She said: “I was plagued by feelings of misery and self-loathing. When I was taking drugs I didn’t shower or even brush my teeth. I just sat in my room on my own.
“I never admitted I was an addict. When I went to rehab it was like a college. We were taken to conference rooms and someone would explain about all different types of drugs and what they do to you.
“It made me think: ‘Why am I messing my life up?’ The only thing wrong with my life was me. I had two choices - keep taking drugs and die or I can stop.”
Kelly empathises with her close friend Amy Winehouse who has also battled drug and alcohol problems.
The 24-year-old star said: “I have known Amy for a really long time. Because of what has happened to me it is easier for me to see through the b.s.
“Amy is a really special and talented person. It is hard to be a woman in this industry.”