Most drugs of abuse decrease the generation of new neurons in the brain, but the effects of marijuana on this process, called neurogenesis, had not been clear.

In a paper appearing online on October 13 in advance of print publication of the November issue of the Journal of Clinical Investigation, Xia Zhang and colleagues from University of Saskatchewan show that a potent and synthetic cannabinoid promotes neurogenesis. This drug also exerts anti-anxiety and antidepressant-like effects.

The researchers suggest that there is a positive correlation between increased adult neurogenesis and modified behavior following chronic cannabinoid treatment. These data expand the existing knowledge about the positive roles cannabinoids and their receptors play in brain processing and medicine. Moreover, cannabinoids are perhaps the only illicit drug that can enhance adult neurogenesis and subsequently modify behavior.

Reference: Cannabinoid promotes embryonic and adult hippocampus neurogenesis and produces anxiolytic- and antidepression-like effects. J. Clin. Invest. 115: 3104-3116 (2005). doi:10.1172/JCI25509.