Research on the relationship between cannabis and mental health is a vivid illustration of the fact that the pace at which new scientific insights are embraced by the community is determined in an idiosyncratic, non-linear fashion. In 1987, a landmark study by Andreasson in the Lancet presented credible confirmation of the classic clinical observation that use of cannabis was associated with onset of psychosis. One would have expected that the link between one of the most widely used psychotropic drugs and one of the most devastating of mental illnesses would have resulted in an animated public health discussion. In actual fact, nothing happened very much. In the ensuing 15 years, however, the cumulative weight of a range of clinical, epidemiological and basic science investigations became such that by 2003 both the scientific and public health communities have gradually become aware of the potential significance of cannabis use.

Therefore, if ever a book was timely and topical, it is this one. The editors have done a remarkable job in bringing together the views of the principal experts in the field from around the world, providing a balanced summary of all the evidence that relates the use of cannabis to mental health outcomes. It includes a comprehensive overview of studies of the direct psychotropic effects of cannabis whilst in other chapters this evidence is elegantly linked to the possible neurobiological mechanisms underlying cannabis-induced mental states.