pharmacologically active cannabinoids has resulted in initiatives to fund research into the potential of cannabinoids for the symptomatic treatment of nausea and vomiting, anorexia, neurogenic and nocigenic pain, seizures, and intraocular pressure.

The use of cannabinoids for treating nausea following chemotherapy is not new. In fact, in Canada, 2 commercially available drugs—dronabinol, which contains chemically synthesized tetrahydrocannabinol (THC), and nabilone, a synthetic cannabinoid—are available by prescription for nausea. These single pharmacological orally administered drugs are unlike smoked marijuana, which has a different pharmacokinetic profile. Other products also are inhaled from burning Cannabis sativa or Cannabis indica plant material. Like most plants, cannabis is a variable and complex mixture of biologically active compounds. The plant contains more than 400 chemicals of which approximately 60 are cannabinoids; the main psychoactive substance sought for recreational use is generally believed to be d⁹-THC. However, varying proportions of other cannabinoids, mainly cannabidiol (CBD) and cannabinol (CBN), may modify the effects of THC or cause effects of their own. Often, research on the adverse health effects of cannabis focuses on the effects of individual compounds rather than on that of marijuana smoked illicitly. For this reason, diametrically opposed opinions have resulted as to whether cannabis is a neurointoxicant or a neurotoxin. Added to this complexity is the long half-life of the cannabinoids, which results in prolonged pharmacological effects, wanted and unwanted.

Dr Solowij addresses the issue of whether prolonged cannabis smoking has a long-term impact on cognitive functioning using electrophysiological methods on individuals who have and have not smoked cannabis. No attempt was made to qualify the source of the material, which would have been impossible under national and international laws and agreements. She addresses the effect of cannabis on cognitive functioning in a scientifically sound manner and shows that, indeed, prolonged smoking results in mild but definite long-term effects on executive function. She also shows that these changes are reversible, indicating probably chronic intoxication rather than neurotoxicity. Her thesis is that duration of cannabis use, not necessarily dosing or frequency, is most important in determining recovery time from cannabis-induced executive-function abnormalities.

This is a well-written, competent and easy-to-read book free of production errors. Within 290 pages Dr Solowij reviews, in the first 5 chapters, our present knowledge of cannabis the drug (forms, routes of exposure, patterns of use, dosage, pharmacokinetics, pharmacodynamics, and mechanisms of action); the acute effects of cannabis on cognitive functioning; evidence for brain damage associated with long-term use of cannabis; and the chronic effects of cannabis on cognitive functioning. Next she reviews the current understanding of attention and event-related potentials (ERPs). The second part of the book details her doctoral research, which documents 5 studies: an event-related potential study of attentional processes in long-term cannabis users; an investigation of the effects of frequency and duration of cannabis use; an investigation of the reversibility of cognitive impairment in former users of cannabis; and a single case study of cessation of cannabis use and the anxiety, psychopathology, and qualitative experience on long-term use. Dr Solowij finishes the book with a concise and effective summary, synthesis, and conclusion.

Hypotheses and discussion of her research results are where Dr Solowij shines. Of particular interest are her comments concerning the cannabinoid receptors (CB1 and CB2) and the discovery of anandamide, an endogenous cannabinoid. In discussing her findings regarding attention and processing changes seen in chronic cannabis users, Dr Solowij raises probably the most important issue in the book: do cannabinoid receptors play an integral part in attention and executive function by upregulating or downregulating the production of specific neurotransmitters?

The monograph obviously represents the work of a doctoral thesis and as such may not be essential for a practitioner’s collection. Conversely, those who are involved in research into illicit drug use or have a special interest in the topic may find this book desirable. Regardless of the preceding comments, this book should be a welcome addition to the stacks in libraries maintaining materials on cognitive functioning. It is unfortunate that more doctoral students do not publish their work in a monograph such as this, particularly when the topic is timely and needs critical evaluation.