Everyone seems to agree that DEMI MOORE was running off the rails before her hospitalization last week.  And now, a source says her bizarre and inappropriate behavior included making a play for 24-year-old ZAC EFRON.

Zac is good friends with RUMER WILLIS . . . and Demi reportedly forced herself into Rumer’s social circle . . . and made a beeline for Zac.

The source says, quote, “She calls him and texts him a lot, but he’s not interested at all.  He thinks she’s a creepy cougar.”

Another source says this is just part of Demi’s desperate attempt to stay young as she approaches 50 . . . quote, “She’s been really down, and she’s surrounding herself with young people to make her feel better.”

And yet another source adds, quote, “Demi was told in the hospital that she has to start eating, which she never does, she only takes Adderall and drinks Red Bull and she doesn’t see how unhealthy that is.

“She’s just obsessed with being young and skinny and trying to keep working and she doesn’t realize how much she’s hurting herself.”

Source: Wise Brother Media