Neil Young has given up smoking cannabis and drinking alcohol to write his forthcoming memoir.

"I did it for 40 years," the singer told the New York Times. "Now I want to see what it's like to not do it. It's just a different perspective."

The 66-year-old said he has been sober for about a year. Although he has epilepsy and suffered a brain aneurysm in 2005, Young used to smoke marijuana "the way others smoke cigarettes," David Carr wrote in the New York Times.

"The straighter I am, the more alert I am, the less I know myself and the harder it is to recognise myself," Young explains in his forthcoming memoir, Waging Heavy Peace. "I need a little grounding in something and I am looking for it everywhere."

Ironically, Young's next album could end up his most mind-altering. Psychedelic Pill features some of his longest jams, including a 28-minute track called Driftin' Back.

Waging Heavy Peace is published in the US on 25 September and in the UK on 11 October. Psychedelic Pill is released on 29 October.