After alcohol and nicotine, marijuana is the most commonly used "recreational" drug in Western countries, though official positions among different countries vary widely. A debate about the medical applications of marijuana and other cannabis-based preparations has been brewing for years, and pressure to legalise such use continues to increase.

In The Science of Marijuana Iversen explains the remarkable advances that have been made in scientific research on cannabis with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the brain. Iversen provides an objective and up-to-date assessment of the scientific basis for the medical use of cannabis and what risks this may entail. The recreational use of the drug and how it affects users is described along with some predictions
about how attitudes to cannabis may change in the future.