Gateway Drug Hypothesis

"The gateway effect, if it exists, has at least two potential and quite different sources (MacCoun, 1998). One interpretation is that it is an effect of the drug use itself (e.g., trying marijuana increases the taste for other drugs or leads users to believe that other substances are more pleasurable or less risky than previously supposed). A second interpretation stresses peer groups and social interactions. Acquiring and using marijuana regularly may lead to differentially associating with peers who have attitudes and behaviors that are prodrug generally, not only with respect to marijuana. One version of this is the possibility that those peers will include people who sell other drugs, reducing the difficulty of locating potential supplies. If the latter is the explanation, then legalization might reduce the likelihood of moving on to harder drugs compared to the current situation."

"The illicit drugs with the largest number of recent initiates in 2016 were marijuana (2.6 million new users), prescription pain relievers (2.1 million new misusers), prescription tranquilizers (1.4 million new misusers), prescription stimulants (1.4 million new misusers), hallucinogens (1.2 million new users), and cocaine (1.1 million new users). In addition, there were 4.6 million new users of alcohol, 1.8 million people who tried a cigarette for the first time in the past year, and 1.2 million people who first used smokeless tobacco in the past year.³⁴

"Figure 12 provides an overview of the average age at first use (or first misuse for prescription drugs) in 2016 among recent initiates aged 12 to 49. For many substances, the average age at initiation in 2016 was younger than age 20, with average ages of 17.4 years for alcohol, 18.0 years for cigarettes, 18.2 years for inhalants, 19.3 years for marijuana, and 19.6 years for any hallucinogen. However, some substances had older average initiation ages, such as methamphetamine (24.6 years) and heroin (25.5 years). The average ages at initiation for prescription drug misuse were in the early to mid-20s (23.9 years for prescription tranquilizers, 24.3 years for prescription stimulants, 24.4 years for prescription pain relievers, and 24.8 years for prescription sedatives)."

"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."

"Our results indicate a moderate relation between early teen marijuana use and young adult abuse of other illicit substances; however, this association fades from statistical significance with adjustments for stress and life-course variables. Likewise, our findings show that any causal influence of teen marijuana use on other illicit substance use is contingent upon employment status and is short-term, subsiding entirely by the age of 21. In light of these findings, we urge U.S. drug control policymakers to consider stress and life-course approaches in their pursuit of solutions to the 'drug problem.'"

"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."

"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."

"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 causal significance of this sequence of initiation into drug use remains controversial. The hypothesis that it represents a direct effect of cannabis use upon the use of the later drugs in the sequence is the least compelling. There is better support for two other hypotheses which are not mutually exclusive: that there is a selective recruitment into cannabis use of nonconforming adolescents who have a propensity to use other illicit drugs; and that once recruited to cannabis use, the social interaction with other drug using peers, and exposure to other drugs when purchasing cannabis on the black-market, increases the opportunity to use other illicit drugs"

"• In 2013, the rate of current illicit drug use among youths aged 12 to 17 who smoked cigarettes in the past month was approximately 9 times the rate among youths who did not smoke cigarettes in the past month (53.9 vs. 6.1 percent). Also, the rate of current marijuana use in 2013 among youths aged 12 to 17 who smoked cigarettes in the past month was about 11 times the rate among youths who did not smoke cigarettes (49.5 vs. 4.6 percent).

"• In 2013, the rate of current illicit drug use was associated with the level of past month alcohol use. Among youths aged 12 to 17 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), 62.3 percent were current illicit drug users and 57.9 percent were current marijuana users. These rates were higher than the rates among youths who were not current alcohol users (4.9 percent for current illicit drug use and 3.3 percent for current marijuana use). Additionally, among youths aged 12 to 17 who were binge but not heavy alcohol users (i.e., consumed five or more drinks on the same occasion on 1 to 4 days in the past 30 days), 46.6 percent were current illicit drug users and 43.2 percent were current marijuana users (with the marijuana use rate being higher than the 2012 rate of 37.8 percent).

"• In 2013, the rate of current illicit drug use among youths aged 12 to 17 who both smoked cigarettes and drank alcohol in the past month was approximately 16 times the rate among those who neither smoked cigarettes nor drank alcohol in the past month (64.5 vs. 3.9 percent). Additionally, the rate of current marijuana use among youths aged 12 to 17 who both smoked cigarettes and drank alcohol in the past month was about 25 times the rate among those who neither smoked cigarettes nor drank alcohol in the past month (59.7 vs. 2.4 percent)."

"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."

"Deviations from normative patterns of drug use initiation that involve the initiation of illicit drug use earlier than usual in the gateway pattern of initiation may carry small risks for dependence, but other factors seem to be more important in the development of drug dependence. Drug use and initiation are clearly nested within a social normative context, yet neither adherence nor deviation from this order signals highly elevated risks of drug problems in and of themselves, although some violations are predicted by pre-existing mental disorders that seem to be more powerful risk factors for subsequent substance dependence. Although a gateway violation might be a marker of such risk factors, their associations with gateway violations are relatively modest. In targeting intervention efforts, it would probably be more productive to screen directly for these factors (i.e. internalizing disorders, early-onset substance use) than to screen for gateway violations."

"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."

"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 present paper examined the extent and ordering of licit and illicit drug use across 17 disparate countries worldwide. This comparison, using surveys conducted with representative samples of the general population in these countries, and assessment involving comparable instruments, allowed for the first assessment of the extent to which initiation of drug use follows a consistent pattern across countries. Previous studies, concentrated in high income countries with relatively high levels of cannabis use, have documented: a common temporal ordering of drug initiation; an increased risk of initiating use of a drug later in the sequence once having initiated an earlier one; and the persistence of the association following controlling for possibly confounding factors (Kandel et al., 2006).

"The present study supported the existence of other factors influencing the ordering and progression of drug use because 1) other illicit drug use was more prevalent than cannabis use in some countries, e.g. Japan; 2) the association between initiation of 'gateway' drugs (i.e. alcohol/tobacco and cannabis), and subsequent other illicit drug use differed across countries, in some instances according to background prevalence of use of these gateway drugs; and 3) cross-country differences in drug use prevalence corresponded to differences in the prevalence of gateway violations.

"Higher levels of other illicit drug use compared to cannabis use were documented in Japan, where exposure to cannabis and tobacco/alcohol was less common. In this case, a lack of exposure and/or access to substances earlier in the normative sequence did not correspond to reductions in overall levels of other illicit drug use. This finding is contrary to the assumption that initiation reflects a universally ordered sequence in which rates of drug use later in the sequence must necessarily be lower than those earlier in the sequence (Kandel, 2002). This has not previously been reported as research has been traditionally conducted in countries where use of tobacco, alcohol and cannabis is relatively common."

"Analysis of the demographic and social characteristics of a large sample of applicants seeking approval to use marijuana medically in California supports an interpretation of long term non problematic use by many who had first tried it as adolescents, and then either continued to use it or later resumed its use as adults. In general, they have used it at modest levels and in consistent patterns which anecdotally-often assisted their educational achievement, employment performance, and establishment of a more stable life-style. These data suggest that rather than acting as a gateway to other drugs, (which many had also tried), cannabis has been exerting a beneficial influence on most."

"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."

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