Contactmusic quoted Kelly as telling 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."
The 24-year-old Kelly has been in rehab four times and is presently drug free.