Gateway Theory

"There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs."

"Our key findings were that 1) there are no unique factors distinguishing the gateway sequence and the reverse sequence — that is, the sequence is opportunistic; 2) the gateway sequence and the reverse sequence have the same prognostic accuracy; and 3) a sizable proportion of substance users begin regular consumption with an illicit drug. These results, considered in the aggregate, indicate that the gateway sequence is not an invariant pathway and, when manifest, is not related to specific risk factors and does not have prognostic utility. The results of this study as well as other studies demonstrate that abusable drugs occupy neither a specific place in a hierarchy nor a discrete position in a temporal sequence. These latter presumptions of the gateway hypothesis constitute what Whitehead referred to as the 'fallacy of misplaced connectedness,' namely, asserting 'assumptions about categories that do not correspond with the empirical world.'"

"The gateway hypothesis holds that abusable drugs occupy distinct ranks in a hierarchy as well as definite positions in a temporal sequence. Accordingly, substance use is theorized to progress through a sequence of stages, beginning with legal, socially acceptable compounds that are low in the hierarchy, followed by use of illegal 'soft' and later 'hard' drugs ranked higher in the hierarchy. One of the main findings of this study is that there is a high rate of nonconformance with this temporal order. In a neighborhood where there is high drug availability, youths who have low parental supervision are likely to regularly consume marijuana before alcohol and/or tobacco. Consumption of marijuana prior to use of licit drugs thus appears to be related to contextual factors rather than to any unique characteristics of the individual. Moreover, this reverse pattern is not rare; it was observed in over 20% of our sample."

"The results of this study suggest that general behavioral deviancy and not specific risk factors accounts for illicit drug use. When illicit drug use occurs first, it is very likely due to the opportunity afforded by the neighborhood environment in context of low parental supervision. The probability and rate of development of a diagnosis of marijuana use disorder and alcohol use disorder were the same whether or not there was conformance with the gateway sequence. Evidence supporting 'causal linkages between stages,' as specified by the gateway hypothesis, was not obtained. Nor were specific risk factors identified that were related to consumption of each drug. Our results indicate that efforts to prevent marijuana use should utilize strategies directed at averting the development of the characteristics prodromal to the manifestation of behavior problems."

The Institute of Medicine's 1999 report on marijuana explained that marijuana has been mistaken for a gateway drug in the past because "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."

More than 100 million Americans have tried marijuana; 14.4 million Americans are estimated to be "past-month" users. Yet there are only an estimated 2,075,000 "past-month" users of cocaine and 153,000 "past-month" users of heroin.

According to the 2007 National Survey on Drug Use and Health:
"In 2007, the average age at first marijuana use among recent initiates aged 12 to 49 was 17.6 years, which was similar to the average in 2006 (17.4 years) (Figure 5.4). Among recent initiates aged 12 or older who initiated use prior to the age of 21, the mean age at first use was 16.2 years in 2007, which was not significantly different from the estimate (16.1 years) in 2006."
"In 2007, the average age at first alcohol use among recent initiates aged 12 to 49 was 16.8 years, similar to the corresponding 2006 estimate (16.6 years). The mean age at first use among recent initiates aged 12 or older who initiated use prior to the age of 21 was 15.8 years, which was the same as the 2006 estimate."
"In 2007, among recent initiates aged 12 to 49, the average age of first cigarette use was 16.9 years, similar to the average in 2006 (17.1 years)."

"In 2007, the rate of current illicit drug use was almost 9 times higher among youths aged 12 to 17 who smoked cigarettes in the past month (47.3 percent) than it was among youths who did not smoke cigarettes in the past month (5.4 percent).
"Past month illicit drug use also was associated with the level of past month alcohol use. Among youths aged 12 to 17 in 2007 who were heavy drinkers (i.e., consumed five or more drinks on the same occasion on each of 5 or more days in the past 30 days), 60.1 percent also were current illicit drug users, which was higher than the rate among nondrinkers (5.0 percent)."

A study in the Journal of the American Medical Association on cannabis and its possible role as a gateway drug found that "While covariates differed between equations, early regular use of tobacco and alcohol emerged as the 2 factors most consistently associated with later illicit drug use and abuse/dependence. While early regular alcohol use did not emerge as a significant independent predictor of alcohol dependence, this finding should be treated with considerable caution, as our study did not provide an optimal strategy for assessing the effects of early alcohol use."

A study in the Journal of the American Medical Association on cannabis and its possible role as a gateway drug concluded that "While the findings of this study indicate that early cannabis use is associated with increased risks of progression to other illicit drug use and drug abuse/dependence, it is not possible to draw strong causal conclusions solely on the basis of the associations shown in this study."

"Other mechanisms that might mediate a causal association between early cannabis use and subsequent drug use and drug abuse/dependence include the following:
"1. Initial experiences with cannabis, which are frequently rated as pleasurable, may encourage continued use of cannabis and also broader experimentation.
"2. Seemingly safe early experiences with cannabis may reduce the perceived risk of, and therefore barriers to, the use of other drugs. For example, as the vast majority of those who use cannabis do not experience any legal consequences of their use, such use may act to diminish the strength of legal sanctions against the use of all drugs.
"3. Alternatively, experience with and subsequent access to cannabis use may provide individuals with access to other drugs as they come into contact with drug dealers. This argument provided a strong impetus for the Netherlands to effectively decriminalize cannabis use in an attempt to separate cannabis from the hard drug market. This strategy may have been partially successful as rates of cocaine use among those who have used cannabis are lower in the Netherlands than in the United States."

In 2002 the English government published research on the initiation of drug use and criminal offending by young people in Britain. According to the study, "After applying these methods, there is very little remaining evidence of any causal gateway effect. For example, even if soft/medium drugs (cannabis, amphetamines, LSD, magic mushrooms, amyl nitrite) could somehow be abolished completely, the true causal link with hard drugs (crack, heroin, methadone) is found to be very small. For the sort of reduction in soft drug use that might be achievable in practice, the predicted causal effect on the demand for hard drugs would be negligible. Although there is stronger evidence of a gateway between soft drugs and ecstasy/cocaine, it remains small for practical purposes. My interpretation of the results of this study is that true gateway effects are probably very small and that the association between soft and hard drugs found in survey data is largely the result of our inability to observe all the personal characteristics underlying individual drug use. From this viewpoint, the decision to reclassify cannabis seems unlikely to have damaging future consequences."

The World Health Organization's investigation into the gateway effect of marijuana stated emphatically that the theory that marijuana use by adolescents leads to heroin use is the least likely of all hypotheses.

According to CASA (National Center on Addiction and Substance Abuse), there is no proof that a causal relationship exists between cigarettes, alcohol, marijuana and other drugs. Basic scientific and clinical research establishing causality does not exist.

The World Health Organization noted the effects of prohibition in its March 1998 study, when it stated that "exposure to other drugs when purchasing cannabis on the black market, increases the opportunity to use other illicit drugs."

In March 1999, the Institute of Medicine issued a report on various aspects of marijuana, including the so-called Gateway Theory (the theory that using marijuana leads people to use harder drugs like cocaine and heroin). The IOM stated: "There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs."

The Institute of Medicine's 1999 report on marijuana explained that marijuana has been mistaken for a gateway drug in the past because "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."