Stevie Nicks has expressed a concern that Prince may have ''purposefully'' overdosed.

The 'Purple Rain' hitmaker tragically passed away at the age of 57 in April last year after he overdosed on fentanyl which he was prescribed after battling with chronic hip pain, and although his death was ruled accidental, his close pal and Fleetwood Mac singer Stevie believes there may be more to the story.

She said: ''I don't know in my heart of hearts whether he just took too much. Or did he purposefully take too much? Did he accidentally take too much?''

The 69-year-old music icon believes Prince was ''isolated'' as he had no children following the death of his son Ahmir a week after his birth in 1996, and no partner.

Stevie added: ''When you get to be our age - and he was younger than me - and you're like 'I'm not making hit records any more ... I'm not able to really tour any more because of my health ...' You're not married, you don't have children ... you don't hang out with a bunch of people because you're really an isolationist.''

The 'Landslide' hitmaker also expressed concern about the strength of fentanyl, and believes Prince's addiction to the prescribed drug ''broke his heart'' as he often preached about ''the downfall of people that do drugs''.

Speaking to the Sunday Mirror newspaper, Stevie said: ''Fentanyl is the worst of the worst of the worst - way stronger than heroin, morphine, anything. And he was having to take it because I think he was probably fractured from his neck down to his feet.

''I think when you're in that much pain and you're somebody who has made it your life's work to preach about the downfall of people that do drugs, that had to be [a burden]. I think that broke his heart.''