Like Heath Ledger, Brad Renfro died as a result of drug overdose ... except Brad's was the really bad kind. "Acute heroin and morphine intoxication" to be exact, according to the coroner's office toxicology results released today.

Not a HUGE shock, considering the kid star's history of drug addiction, including a heroin bust as recently a 2005. But nonetheless sad, and scary, when combined with Heath Ledger's drug-related passing just days after.

Young Hollywood appears to be shaken up by the unexpected deaths, with a number of stars checking themselves in for mental health treatment lately, including Britney Spears and Grey's Anatomy's Justin Chambers, while it's rehab for Eva Mendes, Kirsten Dunst and The Insider's Pat O'Brien.

Ok, lets be honest, Britney is too self-absorbed to know any other celebrity exists, and the rest of these celebs could probably care less about Brad Renfro. But Kirsten Dunst, for one, can attribute at least part of her emotional breakdown to Heath's passing, says an insider:

"She's been crying a lot lately, a lot built up. Everybody hits that bottom where you feel [so] scared that that one heavy night of partying can really wake you up. It's good she's getting herself help.

"She has been partying hard for a while and I'm sure the Heath Ledger thing put people over the edge."

Kirsten is said to be "not doing well" in rehab, but it's still too early to tell. Hope she comes out of there with a better recovery than Lindsay Lohan!

Keywords: Britney Spears, Kirsten Dunst, Heath Ledger, Just Chambers, Brad Renfro, , Psych WardEva Mendes, Pat O' Brien, Lindsay Lohan