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Major Studies of Drugs and Drug Policy
Canadian Senate Special Committee on Illegal Drugs
Volume I - General Orientation

Chapter 6 - Users and uses: form, practice, context

Stepping stone to other drugs?


The stepping stone theory holds considerable sway in debates on marijuana. In fact, the concern is that cannabis use leads to the use of other drugs, in particular, the so-called hard drugs, such as heroin and cocaine.


It logically follows that more people using drugs will increase the number of people being harmed by them. Cannabis is believed to be the foundation upon which most young people begin experimenting with illicit drugs. (…) The “gateway” concept has been around for a long time, and again, although there is no definitive evidence, the National Institute on Drug Abuse has reported that neuro-toxicological research suggests that marijuana “may alter the brain in ways that increase the susceptibility to other drugs.”

Many believe that cannabis use provides the impetus for those people looking to increase the psychotropic effect a drug has on them. [1][51]


We should first define our terms. The “stepping stone” theory holds that cannabis use inevitably leads to use of other drugs. In this theory, cannabis use would lead to neurophysiological changes, affecting in particular the dopaminergic system (also called the reward system), thus creating the need to move on to the use of other drugs. This theory has been completely dismissed by research. We share this conclusion with several international bodies doing drug research, including the British organization DrugScope:


The Stepping-Stone theory has proved unsustainable and lacking any real evidence base. The “evidence” that most heroin users started with cannabis is hardly surprising and demonstrably fails to account for the overwhelmingly vast majority of cannabis users who do not progress to drugs like crack and heroin. The Stepping-Stone theory (often confused among the general public for the Gateway theory) has been dismissed by scientific inquiry. The notion that cannabis use “causes” further harmful drug use has been, and should be, comprehensively rejected. [2][52]


The “gateway” theory suggests that users’ trajectories offer them choices as they start their trajectory of use and that one of these choices is to use other drugs. According to this theory, certain factors, such as early initiation and more regular and heavier use, reinforce this possibility. However, these factors themselves, and early initiation to cannabis in particular, are related to earlier factors, arising from the family environment and social living conditions, that predispose the more vulnerable young people to this early initiation and more rapid progress towards regular and heavy use.


The link between cannabis and other drug use, according to this explanation, is thus a reflection that there are a number of risk factors and life pathways that predispose young people to use cannabis and that they overlap with the life pathways that predispose young people to use other illicit drugs. [3][53]


In addition to these factors that predispose some young people to heavier use of psychoactive substances – including alcohol and tobacco first of all – the sociological conditions under which users can obtain cannabis are such that they are in contact with an environment that is at least marginal if not criminal. Dealers are often the same people who also sell heroin, crack, amphetamines, cocaine and ecstasy such that the probability that a young cannabis user, already more vulnerable due to the factors of his personal trajectory, would come into contact with these other substances more easily. We would also add that wholesalers and dealers “cut” or even mix their products; we were told at times that ecstasy, for example, could contain many things other than MDMA.

Furthermore, if it is true that use of substances such as heroin and cocaine develops almost necessarily out of prior use of marijuana, then it also develops out of the use of other substances, nicotine and alcohol in particular, which are more gateways to a trajectory of use than cannabis.

If we come back to trends in drug use in the population, while more than 30% have used cannabis, less than 4% have used cocaine and less than 1% heroin.

However, it is true that regular and heavy users are more likely than occasional users to use other substances. The study by Cohen and Kaal[4][54] discussed in the previous section shows for example that more than 90% of long-term cannabis users have also used tobacco and alcohol during their lifetime. Above all, it also shows that 48% in Amsterdam and 73% in San Francisco have used cocaine at least once in their life, and 37% in Amsterdam, 77% in San Francisco and 47% in Bremen have used hallucinogens at least once. Nevertheless, no regular cannabis users were regular users of other substances. The authors also show that the most common sequence is alcohol (around age 14), tobacco (around age 15), cannabis (around age 17), followed by other drugs in the early 20s.

We feel that the available data show that it is not cannabis itself that leads to other drug use but the combination of the following factors:

··               Factors related to personal and family history that predispose to early entry on a trajectory of use of psychoactive substances starting with alcohol;

··               Early introduction to cannabis, earlier than the average for experimenters, and more rapid progress towards a trajectory of regular use;

··               Frequenting of a marginal or deviant environment;

··               Availability of various substances from the same dealers.  


[1][51]  M. J. Boyd, Chair of the Drug Abuse Committee and Deputy Chief of the Toronto Police Service, Canadian Association of Chiefs of Police, testimony before the Special Senate Committee on Illegal Drugs, Canadian Senate, first session of the thirty-seventh Parliament, Issue 14, page 75.

[2][52]  DrugScope (2001) Evidence to Home Affairs Committee Inquiry into Drug Policy. Available on-line at: http://www.drugscope.org.uk/druginfo/evidence-select/evidence.htm

[3][53]  Ibid.

[4][54]  Cohen and Kaal, op. cit., page 92-93.

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