During the 12-week study, eligible patients are seen 7-9 times by research raters and psychiatrists. These visits include side effect monitoring, scheduled medication increases, and ratings designed to measure subtle improvement of symptoms. Monthly blood and urine samples are collected for safety and substance abuse monitoring, and neuropsychological testing is conducted at the first and last appointments. Participants are compensated for their participation and receive medication and study-related visits at no cost during the trial. Depending on their level of response to the medication, participants may also be eligible for a 3-month extension phase.