01/18/2007 at 08:15 AM EST
Lindsay Lohan has checked into rehab, she said in a statement Wednesday.
"I have made a proactive decision to take care of my personal health," she said. "I appreciate your well wishes and ask that you please respect my privacy at this time."
A source close to the actress tells PEOPLE: "Lindsay is in a very positive frame of mind and is looking forward to making a positive change in her life."
Lohan, 20, has been filming the thriller I Know Who Killed Me,
and a rep for the movie tells PEOPLE production had already been on hold due to Lohan's recent appendix surgery
. It's uncertain when filming will resume.
"I Know Who Killed Me,
like all films, has insurance," says the rep. "In Lindsay's case, she has a good 13-hour work day. The character she plays requires a good deal of physicality and she's not yet healed (from her surgery) and not yet ready to return."
In December, Lohan's rep told PEOPLE the actress was attending Alcoholics Anonymous
meetings. Later that month, Lohan revealed that she had been in AA for a year
, and said she feels better when she's not drinking.
"I was going out too much and I knew that, and I have more to live for than that," she told PEOPLE.
But Lohan had previously dismissed critics who said she was going out too much. In November, she told Oprah Winfrey that she is
not a party girl
, adding, "Is it a crime to go dancing with your friends?"
Over the summer, James G. Robinson, CEO of Morgan Creek Productions, blasted her for being absent
from the set of her movie Georgia Rule
and blamed her "heavy partying" for the behavior.
Lohan's mother Dina quickly shot back, saying Robinson was "way out of line." Lohan was briefly hospitalized at the time for being "overheated and dehydrated," according to her rep.