“…different cannabis compounds may exert opposite effects on the neuroanatomical changes underlying psychosis. In particular, cannabidiol (CBD) was shown to prevent THC associated hippocampal volume loss… This finding is further supported by several animal experiments supporting neuroprotective properties of CBD mainly via anti-oxidative effects, CB2 receptors or adenosine receptors… mechanisms by which CBD may reduce brain volume loss, including antagonism of THC, interactions with endocannabinoids, and mechanisms that specifically underlie antipsychotic properties of CBD.”

http://www.ncbi.nlm.nih.gov/pubmed/22716143