In healthy volunteers, THC, but not CBD induces anxiety, dysphoria and psychotic symptoms (Martin-Santos et al., 2012).
In one trial, 600 mg of oral CBD significantly reduced anxiety, cognitive impairment and discomfort in a simulated public speaking test (Bergamaschi et al., 2011).
Apart from reducing anxiety, CBD also enhances the extinction of fear memories (Das et al., 2013). Similarly, THC was shown to enhance fear extinction in humans (Rabinak et al., 2013).
Funtional Magnetic Resonance Imaging revealed that the anxiolytic properties of CBD are associated with increased activity in the limbic regions of the brain which are involved in emotional processing (Crippa et al., 2004).
The anxiolytic action of CBD may be mediated by the 5-HT1a receptor (Russo et al., 2005).
Literature:
Bergamaschi, M.M., Queiroz, R.H.C., Chagas, M.H.N., de Oliveira, D.C.G., De Martinis, B.S., Kapczinski, F., Quevedo, J., Roesler, R., Schröder, N., Nardi, A.E., et al. (2011). Cannabidiol reduces the anxiety induced by simulated public speaking in treatment-naïve social phobia patients. Neuropsychopharmacol. Off. Publ. Am. Coll. Neuropsychopharmacol. 36, 1219–1226.
Crippa, J.A. de S., Zuardi, A.W., Garrido, G.E.J., Wichert-Ana, L., Guarnieri, R., Ferrari, L., Azevedo-Marques, P.M., Hallak, J.E.C., McGuire, P.K., and Filho Busatto, G. (2004). Effects of cannabidiol (CBD) on regional cerebral blood flow. Neuropsychopharmacol. Off. Publ. Am. Coll. Neuropsychopharmacol. 29, 417–426.
Das, R.K., Kamboj, S.K., Ramadas, M., Yogan, K., Gupta, V., Redman, E., Curran, H.V., and Morgan, C.J.A. (2013). Cannabidiol enhances consolidation of explicit fear extinction in humans. Psychopharmacology (Berl.) 226, 781–792.
Martin-Santos, R., Crippa, J.A., Batalla, A., Bhattacharyya, S., Atakan, Z., Borgwardt, S., Allen, P., Seal, M., Langohr, K., Farré, M., et al. (2012). Acute effects of a single, oral dose of d9-tetrahydrocannabinol (THC) and cannabidiol (CBD) administration in healthy volunteers. Curr. Pharm. Des. 18, 4966–4979.
Rabinak, C.A., Angstadt, M., Sripada, C.S., Abelson, J.L., Liberzon, I., Milad, M.R., and Phan, K.L. (2013). Cannabinoid facilitation of fear extinction memory recall in humans. Neuropharmacology 64, 396–402.
Russo, E.B., Burnett, A., Hall, B., and Parker, K.K. (2005). Agonistic properties of cannabidiol at 5-HT1a receptors. Neurochem. Res. 30, 1037–1043.