The study will consist of 3 phases: an initial screening phase which must be completed 7 to 14 days prior to randomization; an 8-week double-blind treatment phase; and a 2-week double-blind dose-tapering follow-up phase. After obtaining written informed consent the investigator will initiate washout of prior psychotropic medications. After the washout of prior psychotropic medications has been completed the investigator must ensure that the subject is no longer taking psychotropic medication for at least 14 days prior to the randomization visit. In addition the investigator must ensure that screening visit procedures (with the exception of obtaining informed consent) are completed within 14 days of the randomization visit.