Ozzy Osbourne's short term memory has been damaged by his past alcohol and drug dependencies.

The legendary rocker has always been open about the battles he's faced, and when a fan quizzed him on writing his autobiography Ozzy wasn't shy in admitting he struggled to recollect certain times.

"I can remember the '80s vividly. I think my short-term memory is damaged from all the years of abuse; I don't know what I did four seconds ago but I can remember clearly things that happened when I was a kid," Ozzy revealed to British music magazine Q.

His autobiography I Am Ozzy was released in 2010 and records the Black Sabbath star's meteoric rise to fame, as well as the downside to being in the public eye.

"The '80s was a fabulous decade. I remember thinking 'Wow, this is great. This is going to last forever.' [My wife] Sharon said to me 'You wait until 1990. It'll all change.' I went 'Naah, it can't be that quick.' Sure enough it changed.

"I don't really remember the '90s. I don't know why. My drug addiction and alcohol addiction were absolutely fierce then. I was just going for it full bore, so there was a lot of blackout time," he explained.

Out of all his vices, it's smoking that ranks highest for Ozzy in terms of addictiveness.

Before kicking the habit the 65-year-old star remembers that it didn't matter how ill he was, he'd always find the strength for another cigarette.

"I honestly do think if they discovered tobacco today, then it would be right next to heroin. I mean, I haven't smoked for a quite a while now but it was one of the most addictive substances that I ever put in my body.

"Even if I had a cold, chest infection, pneumonia, I'd still smoke, It's a miracle that I stopped," he added.