Drug use statistics Library Home Home Universiteit van Amsterdam
Peter Cohen (2009), Observation about cannabis use and cannabis policy. Memorandum prepared for the Constitutional Court of Korea on request of Dr Moon, Director of KORIP, Mr Jeong Ho and Mr Jo Donghwan, September 2009.
© Copyright 2009 Peter Cohen. All rights reserved.


Observation about cannabis use and cannabis policy


Dr Donald P. Cohen

Cannabis use in the adult population of Europe is reported by EMCDDA. Its latest report shows like earlier reports that life time cannabis use in European countries varies between 5% and about 35%. Countries that are next to each other can be very dissimilar( Denmark 38%-Germany 23%; Spain 29%-Portugal 12%) or very similar (Holland 23%-Germany 23%, Italy 31% -France 31%).

Also, cities that are in one country and very close to each other may vary quite a lot in cannabis use. For instance, we know that life time cannabis use in Amsterdam is about two times higher than life time cannabis use in Rotterdam altho the two cities are both large ports with diverse urban populations and at a distance of only about 50 miles, no more.[1]

We do not know if differences or similarities between countries reflect the reality in the population, or that these figures are artifacts of the different methodologies used to measure drug consumption in the population. Since this huge methodological problem will not be solved shortly we will have to assume that in all countries consumption of drug use is measured in ways that allow us- somehow- to make cross national comparisons.

We know many more measurements of cannabis and other drug use from Australia, New Zealand, or the United States of America, but for the logic of this short review mentioning these data in not necessary. Such data would not change the content and scope of the reasoning displayed in this text. So, in order to answer the questions below we will to a large extent use drug use data from Europe; only when aswering question 3 will we introduce some data from the United States of America.

This text has as its main topic the following questions:

  1. why do cannabis use figures vary so much between countries but also inside countries?
  2. is it plausible that drug policy has an impact on drug use level in the population?
  3. do all consumers of cannabis have the same patterns of consumption?
  4. will loosening of legal control, like decriminalization of drug/cannabis use, cause a rise of use, frequent drug use patterns or health risks?

Question 1: why do cannabis use figures very so much between countries and inside countries.

The answer to this question is not really known. In circles of government agencies and drug control bodies people are convinced that drug policy matters, and that it is able to impact drug use levels in the populations of Europe.[2] However as I have reasoned extensively elsewhere, plausible indications, let alone proof for this conviction is not available.[3] Drug control functionaries will state that active police involvement , searching and arresting users will either be followed by a decline of drug use, or the absence of a rise,or the flattening of a rise of drug use. However, how do we recognize such effects ? In Sweden where the government has actively sought to suppress cannabis and other drug use, cannabis use levels almost doubled (from 7.1% tot 13.8%) between 1994 and 2004. In France, also with active suppression of cannabis use , we see use level rise from 11% in 1992 tot 31% in 2005. In fact, we see similar rise of cannabis use all over Europe. An important reason for the lack of evidence that drug policy is able to curb drug use is based on the fact that up till now no serious theory is available of why drug policy would influence drug use level, and if it were to do so, how and via what type of process. If there is no theory, science has no way of testing the theory in practice, and understanding is not created. If we take the drug use data that are available , we have no set of reasons nor a set of theories to know why in Spain cannabis use is more than double the cannabis use in Portugal. And why is cannabis use in the Netherlands, with 30 years of legal sales of cannabis, just as much (23%) as in neighboring Germany (23%) where such freedom never existed ? And why is consumption in the adult population of France much higher than in Holland when one expects exactly the opposite?

It will be some time before our understanding of these differences will develop.

Question 2: Is it plausible that drug policy has an impact on drug use levels in the population?

The answer to this question is a serious NO. As shown under question one, differences and similarities of drug use between countries remain up till now without plausible explanation. In almost all the countries we mentioned similar police driven control policies exist, certainly in countries like France, Germany and Sweden. Still use levels vary a lot. The large differences in all drug use (about 100%) between Amsterdam and Rotterdam were described and analysed in detail by Abraham [4] She is not able to supply explanations for these differences that often are much larger than between countries! The differences between Amsterdam and Rotterdam exist in spite of an equal lack of police involvement with cannabis retail. Retailing cannabis is regulated via specialized shops in both cities, where purchase of small quantities (up till 5 gram) is legal. If we want to lay the groundwork for understanding spread , development and variance of drug use in the population we should start to create plausible theories about it. Possible variables for the creation of theory may be

  • demographic (like % of youth in the population, growth and age distribution of population in urban centers)
  • cultural ( anonymous and dynamic urban life styles and fashions versus socially controlled less flexible life styles, mean levels of education, proportion of academia and art related professions)
  • economic ( expense of time to make a living , expense of time for recreation, levels and differentiation of wealth, industrial innovation , the existence of varied commercial and academic ties to the outside world).

Question 3: Do all consumers of cannabis consume this drug the same way, in other words do they all have the same pattern of use?

The answer is no. Just as with alcohol, tobacco or coffee, frequency of use, doses, spread during the day or week or -weekend only- vary considerably. Also people will change pattern during the period in their lives they consume a drug. Some will quickly level off at a low intensity and low dosage of use, while others may develop into intermittent users, using high doses sometimes or more frequently, after which periods of abstinence or infrequent use may follow. In fact, many possible use patterns may be seen. A minority of users will grow into 'experienced users', that is those who have consumed cannabis at least 25 times during their life. In Amsterdam 12% will become an experienced user, in San Francisco almost 40%. There is not a lot research on use patterns, let alone international comparison of cannabis use patterns. But in one of the few that we have, cannabis use patterns in Amsterdam are very much like patterns in San Francisco [5] "It is significant, from a public health perspective, that clear majorities of experienced users in both cities never used daily or used large amounts even during their peak periods, and that use declined after those peak periods. Furthermore, both samples reported similar steady declines in degree and duration of intoxication. Only 6% in each city reported escalation of use over time" (Reinarman et al, 2004)

In the two cities cannabis is highly available, in spite of the fact that in San Francisco open sale and open use is prohibited, and will be followed by arrest and incarceration. In fact, many large cities in the world have widespread, easy and 24 hour availability of cannabis.

Question 4: will loosening of legal control, like decriminalization of drug/cannabis use, cause a rise of use, frequent drug use patterns or health risks?

There is no reason nor data to legitimately think that decriminalization will have much impact on use level or patterns of use. In The Netherlands where decriminalization is applied since 1976, more than 30 years, use in the population is almost identical with use level in Germany where official decriminalization never existed. [6] In France or Italy with no or only rare local decriminalization , use levels are 50% or more higher than in Germany or Holland. Just as we have no evidence at all that severe police suppression will prevent rising use levels, we have no evidence at all that systematic decriminalization will boost use levels .In fact , comparing the Netherlands after its long history of cannabis decriminalization with neighboring countries without such history, will confirm the observation that decriminalization does not seem to be much of a cause of anything. I would like to indicate here that the Dutch Parliament decided to decriminalize cannabis use in 1976 and has maintained decriminalization ever since. In a recent (2009) government report the system of legal access to cannabis is evaluated and the Commission van der Donk concludes that decriminalization of access should be maintained in the future.[7] [8] In 1976 the advantages of cannabis decriminalization were seen as very important. Not only would it prevent cannabis users to be imprisoned and marginalized, it would also deliver an important way of separating the market for opiates (those days related to considerable problems) from the cannabis market. In the years after 1976 we have seen that the user population of opiates remained very small. Life time opiate use in the general population (2008) is estimated at 0,6% and last year opiate use is too small to measure.[9] Such figures show that decriminalization of cannabis is not followed by high use of opiates. Also for other drugs such indications are absent. From a practical point of view conventional repressive drug policy does not seem to have any protective effect, on the contrary. Criminalization may be an important symbolic policy , but it will expose citizens to sometimes serious consequences of criminalization. [10] Often it will burden law enforcement to the point of breaking. Where great numbers of experienced cannabis users are taking part in cultural life, we see that most will live integrated lifestyles within the dominant institutions of their countries. As with alcohol some users may develop into problematic or very frequent users, and in those cases criminalization will greatly worsen their situation, not improve it.

In modern culturally diverse industrialized nations, limiting access of cannabis to a certain age, and certain outlets, will create conditions of control. Nations will not have any control over drug use and drug pricing when they decide to criminalize drug use and react with suppression [11]. Road traffic control is regulation and having institutions to monitor regulation. Making traffic illicit is as impractical as it is impossible, and the same is true for cannabis. Using legal structures to oversee drug use will prevent dangerous qualities of drugs to be retailed. it enables some form of retail modeling and taxation, and will prevent vast criminal markets to develop.

What about health risks of cannabis?

About health risks the Bureau of Medical Cannabis of the Ministry of Health in the Hague says in its Public Health Leaflet [12], that frequent smoking of cannabis may entail some risks for the lungs and in some people may cause an infection of the nose or throat. [13] The Bureau recommends that people with a hereditary indication of schizophrenia first discuss the use of cannabis with their physician. But potential health risks are small compared to the advantages of cannabis. The Bureau of Medical Cannabis recommends that use of cannabis is best if not mixed with tobacco and by using a vaporizer. The Bureau of Medical Cannabis in the Netherlands has a long standing system of monitoring quality of the cannabis that is grown in a large production unit in the north of Holland. Quality is defined a stable strength and absence of moulding or toxic pesticides. The production unit works with a government license and produces hundreds of kilo's of cannabis per year for the government and for the international pharmaceutical industry. In fact, the production capacity of this unit will also be used for an experiment in which retail outlets for recreational use will be provided with their high quality cannabis products. The Dutch government leaflet on best use of cannabis does not contradict the conclusion of a broad overview, published in 2005 [14] nor the conclusions of the Cannabis Report of the Beckley Foundation (2009).[15] "A review of the literature suggests that the majority of cannabis users, who use the drug occasionally rather than on a daily basis, will not suffer any lasting physical or mental harm. Conversely, as with other 'recreational' drugs, there will be some who suffer adverse consequences from their use of cannabis."

Final words

Supreme Court Judge Carlos Fayt of Argentina made a clear and relevant remark when he recently said that "today, the approach of criminalizing drug use is revealing itself to be both ineffective and inhumane." [16] The Argentinian Supreme Court decided that an article of law that proscribes personal possession of a drug, is unconstitutional. This decision opens up the possibility that Argentina may develop decriminalization as a way to not only uphold human rights, but to enable more practical and intelligent regulatory policies where now only blunt suppression is possible.


  1. Abraham, Manja D., Hendrien L. Kaal, & Peter D.A. Cohen (2002), Licit and illicit drug use in the Netherlands 2001. Amsterdam: CEDRO/Mets en Schilt.
  2. See for instance UNODC 2006: "Sweden's successful drug policy".
  3. Cohen, Peter (2008), The culture of the ban on cannabis: Is it political laziness and lack of interest that keep this farcical blunder afloat? Paper delivered to the conference on "Cannabis-growing in the Low Countries," University of Ghent, 3 and 4 December 2007.
  4. Abraham, Manja D. (1999), The impact of urban residency and lifestyle on illicit drug use in the Netherlands. Journal of Drugs Issues, Summer 1999, pp. 565-586.
  5. Reinarman, Craig, Peter D.A. Cohen, and Hendrien L. Kaal (2004), The Limited Relevance of Drug Policy: Cannabis in Amsterdam and in San Francisco. American Journal of Public Health, 2004;94:836–842.
  6. In most States of Federal Germany, no prosecution is initiated if an arrestee has less than 6 grams of cannabis on his/her body.
  7. http://www.justitie.nl/actueel/nieuwsberichten/archief-2009/90702rapport
  8. Adviescommissie Drugbeleid olv Prof dr van der Donk: Geen deuren maar daden. Den Haag 2009
  9. http://www.emcdda.europa.eu/html.cfm/index86748EN.html page 31
  10. Decriminalization is probably quite advantegeous in the conomic sense because it does not take people out of the labour market. And it may save law enforcement costs. But economic considerations play little or no role in this type of symbolic policies or their reform.
  11. It should be remarked that pricing may have an effect on use level but some researchers are not sure: e.g. Hughes remarks in his discussion of tobacco smokers who quit: "However, it is unclear whether this decline[in tobacco use] is a resumption of previous trends or a one time drop due to the increase in cost" In "Those who continue to smoke" page 33 Monograph 15 .US Dept of Health and Human Services, 2003.In our own research on cannabis use not many indications were found that price is a factor in level of use of an individual.
  12. http://www.cannabisbureau.nl/MedicinaleCannabis/Patinteninformatie/default.asp
  13. See for some detailed discussion of this (low) risk ; Hashibe, M., et al. "Marijuana Use and the risk of lung and upper aerodigestive tract cancers: Results of a population-based case-control study," /Cancer Epidemiology, Biomarkers, and Prevention/ 15(10):1829-1834 (2006) W. C. Tan et al., "Marijuana and chronic obstructive lung disease: A population-based study," /Canadian Medical Assn Journal/ 180(8):814-820 (2009).
  14. Leslie Iverson: "Long-term effects of exposure to cannabis"; Current Opinion in Pharmacology, 2005. 5.69-72.
  15. http://www.beckleyfoundation.org/policy/extendedsummary.html
  16. See Intercambios Asociación Civil www.intercambios.org.ar Buenos Aires, September 1, 2009.

CV Dr Donald Peter COHEN (1942)

Dr Cohen was Director of the unit for research of drug use and drug use epidemiology, The Center of Drug Research -CEDRO- at the University of Amsterdam from 1995 until he retired in 2004.

Dr Cohen has been advisor in matters of drug use and drug research to the Dutch Government and the Municipality of Amsterdam between 1981 and 2004. In this period he worked as well as the Dutch representative in the Pompidou Drug Expert Group of the Council of Europe in Strasbourg, and the first three years of its existence as the expert nominated by the European Parliament in the Management Board of the European Monitoring Center for Drugs and Alcohol (EMCDDA) in Lisbon.

In the early 1990's he was the methodological adviser of WHO in Geneva on its global use of cocaine research project.

Dr Cohen was a witness to the Canadian Senate Committee on drug policy and a similar Parliamentary Commission of Belgium. He was member of the Committee for Evaluation and Funding of drug research proposals , created by the french government "Mission Interministerielle de Lutte contre la Drogue et la Toxicomanie"-MILDT- in Paris.

Dr Cohen designed and participated in many large research projects, of which the official national drug use surveys have become the most noted because of their innovative sampling and non response calculations. CEDRO executed research for EMCDDA on the comparability of different nationally used survey methodologies to measure drug use in the general population.
Cohen made CEDRO into a specialized institution for comparative research of drug research methods and of drug use patterns, with a special focus on cannabis , cocaine and amphetamine use. CEDRO's work on theoretical and methodological issues is noted world wide. Dr Cohen worked for several law firms as a witness in matters of tobacco and nicotine.

CEDRO did not survive Amsterdam University cost cutting policies and was stopped in 2004. Its website with large amounts of reports and statistical data is still one of the most visited drug websites in Europe. The website contains a summary list of Dr. Cohens publications.

Last update: May 25, 2016