Barton, 23, has starred in TV's "The O.C.," as well as the movies "St. Trinian's" and "The Homecoming."
People.com quoted Barton's representative as saying the actress is "making improvements" and is "still seeking treatment" without offering any specific details about her illness or condition.
Barton is expected to return to work soon on The CW's new series "The Beautiful Life," the publicist added.
An insider told People.com Barton has left Cedars-Sinai Medical Center where she reportedly was hospitalized after she called police to assist her with an unpublicized health issue.
Moore to attend retreat in to avoid Kutcher's wedding
Yosemite climber falls 30 feet, suffers major injuries