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Book Review of Marijuana and Madnessi
Title: Marijuana and Madness
Author: D Castle and R Murray (editors)
Publisher: Cambridge University Press
Controversies about marijuana have abounded since this reviewer started medical school. Indeed, I can recall in my early years reading Grinspoon and Bakalars Marihuana, the Forbidden Medicine and thinking how a potentially useful medicine for some could be demonized by so many. In the decade or so, research into marijuana has increased exponentially and the debate in the Western world still rages on. Therefore this concise volume focusing on marijuana and psychosis and depression, edited by two very well known academic psychiatrists, is timely and highly relevant.
The first three chapters focus on basic and clinical neurosciences. Chapter one begins with an easy to read neurochemistry review, looking at both endogenous and synthetic cannabinoids. Next is neurophysiology from both animal and human studies, especially the interactions with cannabinoid receptors and various parts of the brains. It is tough reading and not immediately applicable to most clinicians. Chapter three extends the preceding chapter and focuses on human studies of cannabis: affective responses to cannabis, effects on anxiety and cognition and the controversial amotivation syndrome.
Chapter four reviews the mixed results of investigating the association between cannabis and depression, a relatively new area of research. Whilst there is some association between regular heavy use of cannabis and depression, this effect may be very small.
The next four chapters focus on epidemiological and clinical trials looking at the relationship between psychotic symptoms and cannabis. Verdouxs studies form the base of chapter five: non-psychotic people can have transient psychotic symptoms depending on baseline vulnerabilities, and such symptoms occur after cannabis use. Chapter six challenges the concept of a specific cannabis psychosis, pointing out that most of the research is old and has methodological flaws. It is plausible that excessive cannabis use in of itself can cause a clinical psychosis but it would be rare, due to the large amounts needed. The authors emphasise that this is a difficult area to investigate and it shows in the lack of major work in the last ten years addressing this debate.
Chapter seven is excellent and of major relevance to mental health clinicians, drawing on three epidemiological studies from Sweden, Netherlands and New Zealand to conclude that cannabis has some potential causative factor in the onset of schizophrenia. It clearly notes that cannabis is neither sufficient nor necessary to cause schizophrenia and that it is merely a component, whose strength as a causal factor remains to be seen. Chapter eight describes well designed studies conducted only in the last ten years that have confirmed cannabis use as an independent risk factor for psychotic relapse in schizophrenia. This demonstrates how research can sometimes lag behind clinical observation.
The next two chapters go back to the neurosciences with chapter nine exploring the endogenous cannabinoid system and how it may help in investigating schizophrenia. Like all other infant branches in psychiatry, evidence is contradictory at times and clinical applications highly speculative. Chapter ten looks at pharmacological trials of THC in healthy controls and patients with schizophrenia. What this reader concludes is that it is complicated and involves more than just dopamine!
Chapter eleven is excellent in outlining a motivational model of cannabis use in psychosis that goes beyond a simple self medication hypothesis. Chapter twelve reminds us of the lack of empirical evidence when it comes to treating dual diagnosis patients. It discusses standard treatment such as the cycle of change, motivational interviewing and harm reduction, but does not offer anything groundbreaking. The last chapter looks at long term cognitive effects of cannabis and how short term cognitive deficits have been extrapolated to say cannabis has long term deleterious effects. The authors conclude that there are many confounders preventing proper investigation of the long term effects of cannabis.
The contributors of this volume come from a wide variety of backgrounds and countries. It is good to see the strong presence of Australian authorship and the impressive research in this field coming out of both New Zealand and Australia. The chapters are of digestible length and easily accessible for the busy clinician. The references were comprehensive and up to date. For the clinician of whatever level of training, specialty or sub-specialty, this book will provide some valuable knowledge and insight. For the trainee preparing for examinations it provides more than enough up to date information on a controversial issue. Given the continuing research in this area, future editions would not be missed.
(we've cached a local copy here for easy of access)