1. A method for facilitating consolidation of extinction learning to treat an anxiety disorder, comprising administering to a subject in need thereof: (a) extinction training; and (b) a therapeutically effective amount of D-cycloserine; wherein said D-cycloserine is administered at a time that is both greater than four hours after said extinction training and within two hours prior to onset of the subject's initial nightly sleep period subsequent to said extinction training; and wherein said D-cycloserine is administered on an achronic basis.