Jim Carrey's on-again/off-again 28-year-old girlfriend has committed suicide ... TMZ has learned.
Law enforcement tells TMZ, LAPD responded to a call in the L.A. area Monday night. We're told they went to a residence and found the body of Cathriona White.
Our sources say White left a suicide note addressed to Carrey which references their break up on Sept. 24. Cathriona tweeted on the 24th ... "Signing off Twitter, I hope I have been a light to my nearest and dearest."
Law enforcement tells us they believe she died from an overdose of drugs -- pills were next to her body. We're told 2 friends found Cathriona last night when they went to check on her.
53-year-old Carrey and White met in 2012, dated a few months and then split. They rekindled their relationship in May.
Story developing ...