Dope may help the growth of new brain cells. According to Xia Zhang of the University of Saskatchewan and his colleagues, cannabinoids promote neurogenesis in embryonic and adult rats, and produce anxiolytic- and antidepressant-like effects.1 This is widely different from effects seen for other drugs of abuse, such as nicotine, heroin, and cocaine, which suppress neurogenesis.
Zhang's team analyzed the effect of the synthetic cannabinoid HU210, an agonist of the cannabinoid receptor CB1, on neural progenitor cells in the hippocampal dentate gyrus. HU210 increased cell proliferation in vitro and in vivo after chronic treatment. Antidepressants produce a similar pattern of cell proliferation, inspiring the authors to examine the influence of HU210 on behavior, writes Ronald Duman, molecular psychiatrist at Yale University School of Medicine, in an E-mail.
Using a novelty-suppressed feeding test and a forced swimming test, the authors found that HU210 produced effects similar to those of antidepressants and anxiolytics. Furthermore, irradiating the hippocampus blocked the agonist's effects on both neurogenesis and behavior. The authors suggest that neurogenesis may be promoting the antidepressant and anxiolytic effects.
But, "there is limited clinical evidence demonstrating that cannabinoid administration produces an antidepressant response," says Duman. "Thus, it's difficult to conclude that the current studies indicate and support a therapeutic action of CB1 agonists."