As noted in Chapter 11, to say marihuana leads to any other drug avoids the real issue and reduces a complex set of variables to an oversimplified premise of cause and effect. If any one statement can characterize why persons in the United States escalate their drug use patterns and become polydrug users, it is peer pressure. Indeed, if any drug is associated with the use of other drugs, including marihuana, it is tobacco, followed closely by alcohol. Study after study which the Commission reviewed invariably reported an association between the use of tobacco, and, to a lesser extent, of alcohol with the use of marihuana and other drugs.

The fact should be emphasized that the overwhelming majority of marihuana users do not progress to other drugs. They either remain with marihuana or foresake its use in favor of alcohol. In addition, the largest number of marihuana users in the United States today are experimenters or intermittent users, and 2% of those who have ever used it are presently heavy users. Only moderate and heavy use of marihuana is significantly associated with persistent use of other drugs.

Some persons in our society are interested in experimenting with a series of drugs, and there is no uniformity regarding which drug these multidrug users take first. In some cases, the drug used is a matter of preference; in others, a matter of availability; and in further instances, it matter of group choice.

Citizens concerned with health issues must consider the possibility of marihuana use leading to use of heroin, other opiates, cocaine or hallucinogens. This so-called stepping-stone theory first received widespread acceptance in 1951 as a result of testimony at Congressional hearings. At that time, studies of various addict populations repeatedly described most heroin users as marihuana users also. The implication of these descriptions was that a causal relationship existed between marihuana and subsequent heroin use. When the voluminous testimony given at these hearings is seriously examined, no verification is found of a causal relationship between marihuana use and subsequent heroin use.

Again, we must avoid polarity on this issue. To assume that marihuana use is unrelated to the use of other drugs would be inaccurate. As mentioned earlier, the heavy or very heavy marihuana users are frequently users of other drugs. The stepping-stone theory holds that the adolescent begins the use of illicit drugs with marihuana, and later proceeds to heroin in the search for greater thrills. The opposing viewpoint holds that the large majority of marihuana users never become heroin addicts and denies the validity of a causal relationship.

In the National Survey, among the adult respondents, 70% thought that marihuana makes people want to try stronger drugs such as heroin; 56% of the youth in the 12-to-17-year-old category agreed with the same statement. These perceptions contrast with another finding in the same Survey which revealed that 4% of current marihuana users have tried heroin. On the other hand, very few respondents perceived alcohol and tobacco to be precipitants of other drug use.

Studies of the escalation process demonstrate that the rates of progression vary from one group to another and from one segment of the population to another. There is no set proportion of marihuana users who "escalate" to the use of other drugs. The other drugs which some marihuana smokers use vary according to the social characteristics of the population in question. Within some groups, heroin may be the choice; in other groups, it may be LSD.

Marihuana use per se does not dictate whether other drugs will be used; nor does it determine the rate of progression, if and when it, occurs, or which drugs might be used. As discussed in Chapter 11, the user's social group seems to have the strongest influence on whether other drugs will be used; and if so, which drugs will be used.