Regulation of adult neurogenesis by cannabinoids

In the adult mammalian brain, new neurons are born throughout life, and these new cells may influence learning, memory, olfaction, and even mood. The putative function of these new neurons suggests that manipulation of adult neurogenesis could be used therapeutically in the future, and emphasizes the importance of understanding how neurogenesis is regulated. Voluntary exercise and antidepressants are examples of factors that increase neurogenesis, while stress and drugs of abuse - alcohol, nicotine, psychostimulants, opiates - decrease neurogenesis. In contrast to the clear negative influence of these drugs of abuse, cannabinoids have mixed influence, with some marijuana-like compounds actually enhancing neurogenesis. Here we review the literature in an effort to clarify the controversial impact of cannabinoids on adult neurogenesis. Taking into account key differences in endogenous versus exogenous cannabinoids and nonspecific influence of various cannabinoid compounds, we conclude that cannabinoid influence on neurogenesis is less controversial than initially appears.