Anxiety disorders, such as PTSD, are difficult to treat because many patients only partially respond to CBTs (Cloitre, 2009; Foa, 2000; van Minnen et al., 2002) and even fewer respond to first-line pharmacological treatments, such as selective serotonin reuptake inhibitors (SSRIs) (Stein et al., 2009; Stein et al., 2006). Interestingly, poor extinction retention and vmPFC-HPC dysfunction have been implicated in anxiety disorders such as PTSD and could undermine the maintenance of the therapeutic effects of exposure (Charney and Deutch, 1996; Foa, 2000; Milad et al., 2009; Orr et al., 2000; Pitman et al., 2001; van Minnen and Hagenaars, 2002). Given that enhancing cannabinoid transmission, via CB1 agonists, helps extinction recall, the cannabinoid system is a promising target for improving the learning that goes on in psychotherapy and improving the likelihood of success and its maintenance in patients with PTSD, and other difficult-to-treat anxiety disorders. Moreover, proof-of-concept studies such as this will provide the necessary bioassay of THC’s putative anxiolytic effects and enhance the pace of drug development of cannabinoid modulators (agonists such as THC, or FAAH inhibitors such as URB597).
