Recent research suggests that recreationally used cannabis does not act as a gateway drug to harder drugs such as alcohol, cocaine and heroine. The same will apply to users of medicinal cannabis.

Several research studies addressed the question whether cannabis leads to the use of harder drugs such as alcohol, cocaine and heroin.

According to a study to be published by the Centre for Economic Policy Research, London, cannabis does not lead to the use of hard drugs (Sunday Times of 16 December 2001). Findings are based on a survey of drug users in Amsterdam over a 10-year period. The study by Jan van Ours of Tilburg University in the Netherlands shows that cannabis users typically start using the drug between the ages of 18 and 20, while cocaine use usually starts between 20 and 25. But it concludes that cannabis is not a stepping stone to using cocaine or heroin. Four surveys, covering nearly 17,000 people, were carried out in Amsterdam in 1987, 1990, 1994 and 1997. The study found that there was little difference in the probability of an individual taking up cocaine as to whether or not he or she had used cannabis. Although significant numbers of people in the survey did use soft and hard drugs, this was linked with personal characteristics and a predilection to experimentation.

The Institute of Medicine study characterized marijuana’s role as a “gateway drug” as follows:

"Patterns in progression of drug use from adolescence to adulthood are strikingly regular. Because it is the most widely used illicit drug, marijuana is predictably the first illicit drug most people encounter. Not surprisingly, most users of other illicit drugs have used marijuana first. In fact, most drug users begin with alcohol and nicotine before marijuana—usually before they are of legal age.

In the sense that marijuana use typically precedes rather than follows initiation of other illicit drug use, it is indeed a "gateway" drug. But because underage smoking and alcohol use typically precede marijuana use, marijuana is not the most common, and is rarely the first, "gateway" to illicit drug use. There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs. An important caution is that data on drug use progression cannot be assumed to apply to the use of drugs for medical purposes. It does not follow from those data that if marijuana were available by prescription for medical use, the pattern of drug use would remain the same as seen in illicit use" (Joy et al. 1999)

A more recent study based on national survey data also does not support the hypothesis that increases in marijuana use lead to increased use of more dangerous drugs among the general public. In the American Journal of Public Health, Andrew Golub and Bruce Johnson of the National Development and Research Institute in New York wrote that young people who smoked marijuana in the generations before and after the baby boomers do not appear to be likely to move on to harder drugs. The researchers said that these findings suggest that the gateway phenomenon reflects norms prevailing among youths at a specific place and time.

“The recent increase in youthful marijuana use has been offset by lower rates of progression to hard drug use among youths born in the 1970s. Dire predictions of future hard drug abuse by youths who came of age in the 1990s may be greatly overstated” (Golub & Johnson 2001).

Research also suggests that the “gateway theory” does not describe the behavior of serious drug users:

“The serious drug users were substantially different from high school samples in their progression of drug use. The serious drug users were less likely to follow the typical sequence identified in previous studies (alcohol, then marijuana, followed by other illicit drugs). They were more likely to have used marijuana before using alcohol, and more likely to have used other illicit drugs before using marijuana. We also found that atypical sequencing was associated with earlier initiation of the use of illicit drugs other than marijuana and greater lifetime drug involvement. These findings suggest that for a large number of serious drug users, marijuana does not play the role of a 'gateway drug'. We conclude that prevention efforts which focus on alcohol and marijuana may be of limited effectiveness for youth who are at risk for serious drug abuse” (Mackesy-Amiti et al. 1997)

References

Mackesy-Amiti ME, Fendrich M, Goldstein PJ. Sequence of drug use among serious drug users: typical vs atypical progression. Drug Alcohol Depend 1997;45(3):185-96.
Joy JE, Watson SJ, Benson JA, eds. Marijuana and medicine: Assessing the science base. Institute of Medicine. Washington DC: National Academy Press, 1999.
Golub A, Johnson BD. Variation in youthful risks of progression from alcohol and tobacco to marijuana and to hard drugs across generations. Am J Public Health 2001;91(2):225-32.