Cannabidiol (CBD) is a component of herbal cannabis that is present in varying concentrations in cannabis extracts. CBD has been shown to produce central effects including hypnotic, anticonvulsive, anxiolytic and neuroprotective effects.The investigators hypothesize that treatment with CBD will result in: 1) Improvement evidenced by a reduction in scores on the Positive and Negative Syndrome Scale for Schizophrenia (PANSS), 2) Improvement evidenced by a reduction in the Clinical Global Impression of Severity scale (CGI); Secondary Hypothesis: 1) Greater improvement in functioning as measured on the "Patient Assessment of Own Functioning Inventory: (PAOFI) and the Quality of Life Scale (QLS) In this 2 period cross over design, subjects will be randomized in a 1:1 ratio to receive either: Order 1: CBD (Period 1) followed by placebo (Period 2) or Order 2: Placebo (Period 1) followed by CBD (Period 2) under double-blind conditions. The 2 study periods will be separated by a washout of at least 2 weeks. During each period subjects will receive study medications (CBD [total 800mg/day] or placebo) for a period of 4 weeks.