The 'Cool for the Summer' singer checked into rehab in 2010 at the age of 19 to be treated for alcohol and drug abuse, as well as an eating disorder and persistent self-harming.
Demi, now 23, has never fallen off the wagon since confronting her demons head on and she decided to log on to Twitter to share her achievement with her 34.9 million followers.
She tweeted: "This last year I experienced so much life and too much death ... But I made it through ... Sober. #4Years #GodsWill (sic)
Another cryptic tweet which seemed to refer to the cycle of life, read: "Most people die but others just go ... She's still out there and the chasm grows ... Steady are the feet in the morning glow. (sic)"
Demi also urged her fans to believe "anything is possible" because during her darkest days she never believed she would get clean and turn her life around.
The pop star tweeted: "I can't believe I have 4 years on Tuesday ... Anything is possible."
Demi didn't specify what deaths she was referring to in 2015 but she was left heartbroken by the passing of her and her boyfriend Wilmer Valderrama's pet dogs Buddy - who was killed by coyotes last July - and Doberman Spawn.
brands : Rehab, Facing addiction, Instagram