the chicken or the egg

 

cannabis & schizophrenia

Many research studies have focused on the relationship existing between psychosis and cannabis abuse. However, researchers have constantly come up against the question of determining which problemcaused the other one.

A meta-analysis (1) published in The Lancet sheds new light on this issue.ght on this issue. When the question of possible relationship between cannabis use and psychoses, schizophrenia in particular, first arose, this subject very quickly became the subject of medical observations and research.

"The potential long-term hazardous effects of cannabis with regard to psychosis seem to have been overlooked, and there is a need to warn the public of these dangers, as well as to establish treatment to help young, frequent cannabis users"

In 1845, French psychiatrist, Moreau de Tours, described the intoxicating powers of cannabis (2). Since then, many cases of cannabis-related acute psychosis syndromes have been described in countries where drug use is commonplace ( Maghreb , India ), and in Western countries as well ( USA , Sweden ).

Two questions arose then: the first one aimed at discerning the difference between acute conditions and the predictable symptoms of a real schizophrenia. In other words, were the observers in presence of the precursor signs of schizophrenia or, was it a sole, transitory, cannabis-related, psychotic episode.

The second question aimed at establishing causality between cannabis consumption and the occurrence of a psychotic disease. To put it simply, if people vulnerable to schizophrenia start using marijuana to relieve their symptoms, psychosis would then originate cannabis use rather than reverse, a link which is evidenced by the high proportion of cannabis users among schizophrenic patients - nearly 40%. Schizophrenia is a devastating disease: patients affected are confronted with intense and painful social, professional and emotional disaffiliation and, accordingly, find themselves exposed to a suicide risk factor 20 times higher than the average.

The characteristics of schizophrenia and its dramatic consequences in the lives of those affected justifies the interest of conducing research studies on its relationship with cannabis use, given that cannabis is the most widely used drug worldwide. Almost 160 million people use cannabis, the equivalent of 3.8 per cent of the global population aged 15 to 64 (3).

The Lancet recently published the most comprehensive research study to date of a possible causal relation between cannabis use and psychotic illness later in life (4). The authors were able to adjust for instances in which psychotic outcomes were not, in fact, due to the transitory effect of cannabis intoxication. – a factor that had clouded some previous studies.

The authors concluded that the risk of psychosis increased by roughly 40% among all people who have used cannabis, and 50-200% in the most frequent users. The Lancet stresses that the ultimate evidence for a causal relation would be a larger-scale, placebo-controlled trial of cannabis exposure to healthy young people. However, since cannabis is illegal in most countries, and its harmful effects on cognitive function are already well established, such a trial cannot be done for both ethical and practical reasons.

In its Comment pages The Lancet concludes, "In the public debate, cannabis has been considered a more or less harmless drug compared with alcohol, central stimulants and opioids. However, the potential long-term hazardous effects of cannabis with regard to psychosis seem to have been overlooked, and there is a need to warn the public of these dangers, as well as to establish treatment to help young, frequent cannabis users."

Suzana Lastra
Consultant to Dianova International

(1) A meta-analysis combines the results of several studies that address a set of related research hypotheses. Analyzing the results from a group of studies can allow more accurate data analysis. .

(2) "Of Haschish and Mental Alienation" - Jacques-Joseph Moreau de Tours, 1845

(3) 2007 World Drug Report (pdf. in English)
Report Summary (Spanish)
Press release, in French:

(4) The Lancet - volume 370, 28 July 200