Brief Summary:

The Primary objective of this study is to evaluate Seroquel XR in the treatment of borderline personality disorder (BPD). As in many initial randomized control trials, the study will be of relatively short duration - 8 weeks - to assess effectiveness and safety while maximizing retention. The specific aim is to determine if Seroquel XR is superior to placebo. The primary outcome measure will be a statistically significant difference between Seroquel XR compared to placebo on the Zanarini Rating Scale for Borderline Personality Disorder (ZAN-BPD), an objective rating scale that addresses the severity of Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) symptoms of the illness. As there is the recent development of an extended release form of Seroquel (Seroquel XR) (Schulz et al. 2007), the new compound may offer several advantages in this study. Therefore, the hypothesis of this study is that both doses of Seroquel XR (see below) will be superior to placebo in an 8-week randomized trial as assessed by the ZAN-BPD.

To achieve the Primary Objective of this study, two doses of Seroquel XR will be tested - 150 mg/d and 300 mg/d. Thus, the study will be able to assess the effect of Seroquel XR compared to placebo and to explore a dose effect.