2.1. Primary Outcome Variable-psychopathology: Assessment instruments include the Positive and Negative Syndrome Scale (PANSS) (Kay et al, 1987), the Assessment of Negative Symptoms (SANS) (Andreasen 1981) and the Clinical Global Impression (ICG). Patients are interviewed at screening, at week-4, at week-1, at baseline and at every two weeks, for a total of 12 ratings.