Multiple Drug Use

2015

In this post attention is focused on multiple drug use or the reported use of at least two of the drug classes examined in this study. This is an initial report, and the question whether use of one drug leads to or “causes” use of another drug is not addressed, but the data can be used to establish the temporal order of usage.

Use of pairs of drugs

One tactic used by previous researchers to study multiple drug use is to examine all of the possible combinations of drug classes, note how many cases are observed for each combination and determine if some combinations are observed more frequently than would be expected by chance. As an example, one possible pattern is that none of the nine drug classes were used. It should be noted that in this and later analyses in this chapter, quasi-medical use of stimulants, sedatives and opiates was treated as no use of the drugs. In addition, there are nine different patterns in which one, and only one, drug class was used. If one adds the patterns in which two, three or more of the nine classes were used, the total number of possible patterns is 512. Only 86 of the 512 patterns actually emerged. This clearly established that it is not a matter of chance which drugs are found together in the drug histories of the men in the sample.

Some 78 percent of the respondents were included in the ten pure scale types of multiple drug use that are shown in Table “Number and Percent in Each of Ten Pure Scale Type Patterns of Ever-Never Use”. By far the most prevalent pattern, including 33 percent of the respondents, involved use of only alcohol and tobacco. Another numerically prominent pattern involved use of tobacco, alcohol and marihuana; 22 percent of the sample fitted this pattern. Only 2 percent of the men reported no use of any drug, while 4 percent reported use of drugs in all nine categories.

A second tactic that has been used to study multiple drug involvement is to examine the percentage of persons who report use or nonuse of one drug in terms of reported use of another drug. However, before a detailed analysis of the data in Table “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs” is presented, it is appropriate to offer a general interpretation. An examination of the pairs of columns for each drug, in which users of the drug are compared with nonusers, confirms that use of any drug is associated with use of all other drugs. This can be illustrated by examining the data for users and nonusers of tobacco and alcohol. Most tobacco users have used alcohol but so have most nonusers; so this finding means little. Some 59 percent of the tobacco users report having used marihuana, in comparison with 27 percent of those who have never used tobacco. This finding is interesting from two perspectives. First, use of tobacco is correlated with marihuana use. Second, approximately one-fourth of those who have never used tobacco report having used marihuana, and almost all of them smoked marihuana. Thus, use of tobacco is not a necessary precursor of marihuana use.

Two points should be mentioned about the users and nonusers of alcohol. Since practically all of the respondents have used alcohol, the percentages for nonusers are based on a small number and are perhaps unstable. It is also evident that use of alcohol is associated with use of the other drugs: 57 percent of alcohol users have also used marihuana, 23 percent psychedelics, 24 percent stimulants, 17 percent sedatives, 6 percent heroin, 20 percent opiates and 14 percent cocaine, while nonusers of alcohol rarely used any other drug, except tobacco.

Further discussion of the data in Table “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs” will focus on marihuana, heroin and cocaine. An important inference is that marihuana may be a key drug in understanding multiple drug use. Evidence for this can be found in two places in Table “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs”. The first is in the column indicating the percentages of users and nonusers of marihuana who reported using the other drugs. The second location is in the third row where the percentages of users and nonusers of the other drugs who had also used marihuana are shown; these percentages are markedly different. Some 40 percent of those who had used marihuana had used psychedelics, while virtually none of the nonusers reported psychedelic use. The comparable figures for stimulants were 41 and 1 percent; for sedatives, 29 and 1 percent; for heroin, 11 percent and less than 1 percent; for opiates, 33 and 4 percent. Finally, 25 percent of the marihuana users reported having used cocaine in comparison with almost none of those who have not used marihuana. In three comparisons between users and nonusers of marihuana, fewer than 1 percent of the nonusers had ever used psychedelics, heroin or cocaine. If it can be shown that use of marihuana predates use of the other drugs, a plausible hypothesis would be that use of marihuana, along with a number of other factors, facilitates in some way the movement of a person into use of other substances.

An examination of the figures in row 3 of Table “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs” also suggests this conclusion, though from a slightly different perspective. Of those who had ever used psychedelics or cocaine 100 percent had also used marihuana; this was also true for 97 percent of those who had used stimulants or sedatives, 91 percent who had used opiates, and 99 percent of those who had used heroin. Among the nonusers of these drugs, the percentages reporting use of marihuana ranged from 42 to 52 percent.

There are several reasons for suggesting marihuana rather than alcohol as a key to the understanding of multiple drug use. All users of marihuana used alcohol, and almost all of them used tobacco. Thus, to know that a man has used marihuana is to know that he has used at least alcohol, and probably tobacco; if these are accepted as drugs, marihuana use means multiple drug use.

Second, while the associations of alcohol use with use of other drugs are strong, those of marihuana with other drugs are even stronger. More importantly, marihuana use is a more useful predictor of other drug use than is alcohol use. For nonusers of either drug, one can predict with a high probability of being correct that they will not have used other drugs. With respect to alcohol, one is making a prediction about 3 percent of the sample, but with respect to marihuana 45 percent of the men are involved.

This conclusion applies not only to the associations based on the simple distinction between having used and not having used a drug, but also when the measures of extent of use are examined; the associations of marihuana use with the other drugs are stronger than the associations of alcohol use with them.

Finally, some drugs, for example, stimulants, showed stronger associations with use of other drugs than did alcohol and marihuana. However, it will be shown that in terms of temporal order, use of alcohol and marihuana almost always preceded use of other drugs. Because of the temporal order, it is appropriate to predict from marihuana use to use of the other drugs, but it is only in a statistical sense that one can predict marihuana use from use of drugs such as the stimulants.

Another conclusion suggested by the data in Table “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs” is that use of heroin signifies the deepest involvement in the drug milieu. Persons who had ever used heroin were likely to have used all or most of the other drugs. At least 99 percent of those who had used heroin had also used tobacco, alcohol and marihuana, and at least 80 percent had used psychedelics, stimulants, sedatives, opiates and cocaine. As indicated in Table “Number and Percent in Each of Ten Pure Scale Type Patterns of Ever-Never Use”, 99 respondents or 4 percent of the sample had used all nine classes of drugs studied. Thus, only 49 of the 148 persons who reported having used heroin had not used all of the other drugs. Stated differently, 67 percent of the men who have ever used heroin have also used all of the other drugs studied.

It is also apparent that those who had used cocaine were likely to have used all of the other drugs, except heroin. The data to support this conclusion are found in the last two columns and last row of Table “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs”. First, the percentages of users of cocaine who had also used tobacco and alcohol were high although the percentages for nonusers were almost as high. Second, 100 percent of the users but only 48 percent of the nonusers of cocaine had also used marihuana; this is a ratio of two to one. Third, 89 percent of the cocaine users in comparison with 11 percent of nonusers had tried psychedelics. Among those who had used cocaine, at least 70 percent had also used stimulants, sedatives and opiates, while the comparable percentages for nonusers are approximately 10 percent. Fourth, only 39 percent of the men who had used cocaine had also used heroin; on the other hand, 90 percent of those who had used heroin reported use of cocaine.

Several disclaimers are needed at this point. First, these data do not show, nor are they intended to suggest that use of marihuana or any other drug automatically leads to subsequent use of other drugs. Second, the data contained in Tables “Number and Percent in Each of Ten Pure Scale Type Patterns of Ever-Never Use” and “Percent of Users and Nonusers of Each Drug Who Have Used the Other Drugs” utilize only the crudest of measures. In subsequent analyses of these data, lifetime extent of use, frequency and amounts of use within years and across years as well as patterns of starting and stopping will be examined. Third, in future reports an attempt will be made to integrate the analysis of multiple drug use and onset of use for pairs of drugs with other events such as marriage and education.

Year of onset

In this section the temporal order of the use of pairs of drugs is examined. One of the major methodological weaknesses of most studies of multiple drug use is the failure to date the initial use of different drugs. Goode () clearly makes the point in talking about whether marihuana leads to the use of other drugs, particularly heroin:

We very rarely know in any of these studies precisely when a given subject uses marihuana for the first time, begins using it regularly, and then when he or she initiates heroin use. From the bulk of the studies now available, all we know is that respondents who use marihuana tend to also be those who use heroin. Both could have been initiated at the same time, or either before the other. In order to get a clearer picture of the process of the progression from cannabis to dangerous drugs, we would have to have a detailed picture of the natural history, or the drug “career” of large numbers of users; the drug “biography,” in time sequence, should be on the agenda of any researcher exploring this question.

The specific agenda items recommended by Goode, natural history and time sequence of drug use, were of central importance in this study. Not only are the dates of first and last use for each drug class available, but frequency and quantity patterns were also obtained for each year of use. In addition, because drug use constitutes only one aspect of a biography, the respondents were asked to state the year in which they first ran away from home, were suspended or expelled from school, dropped out of school, owned a car, had sexual intercourse and experienced other events. Questions were also asked about the respondent’s involvement with and attachment to parents, peers and school at ages 13 and 16. In subsequent reports the answers provided to these questions will be brought to bear on such complex issues as the natural history of drug use, multiple drug use and the sequence of drug use. For this initial report attention is focused on the temporal order of initial use of pairs of drugs.

For all men who ever used one of eight drug classes, the year of first use was ascertained, and for those who used any drug 10 or more times, the month and year of initial use were recorded. For tobacco, only the year was noted.

The year of first use of each drug was examined according to the year of first use of all other drugs, except tobacco. The men whose use of stimulants, sedatives and opiates was quasi-medical were treated as nonusers of these drugs. Whenever the respondents indicated that the year of first use for a pair of drugs was the same, a month-by-month table was constructed to eliminate ties. For those who used one or both drugs in a pair less than 10 times, the month of June was arbitrarily assigned as the month of onset, but there were few ties among the experimental users.

It is clear that among the men who had ever used alcohol and at least one of the other drugs, alcohol was almost always the first drug used (). For example, of the men who had ever used alcohol and marihuana, 93 percent used alcohol first. The percentages are even higher when initial use of alcohol is compared with onset of use of the other drugs. Therefore, it may be concluded that use of alcohol precedes use of the other drugs for almost all men who have ever used alcohol and some other drug.

Some 80 percent of the men who had used both marihuana and psychedelics used marihuana first. Use of marihuana was antecedent to the use of stimulants, sedatives and opiates for at least 70 percent of the men who had used marihuana and one or more of these drugs. Some 96 percent of those who have used cocaine and marihuana used marihuana first, while 90 percent of those who have used both heroin and marihuana used marihuana prior to their use of heroin. Use of marihuana did not precede stimulant and opiate use as often as it did use of psychedelics, sedatives, heroin and cocaine. While these data do not show that use of marihuana leads to use of heroin or cocaine, it is apparent that use of the one drug usually preceded the other in time. This fact suggests that use of marihuana cannot be dismissed as a possible, perhaps even probable, cause of use of other drugs, particularly heroin and cocaine.

The temporal order of initial use of psychedelics and the other drugs varies.   Only for heroin and cocaine was the likelihood high that use of psychedelics was antecedent. Of the men who had used psychedelics and stimulants, 46 percent used stimulants first in comparison with 36 percent who used psychedelics first. Among the men who had used psychedelics as well as stimulants, sedatives or opiates, almost one-fifth used psychedelics and these other drugs for the first time in the same month.

Initial use of stimulants was antecedent to use of heroin or cocaine for about three of four men who had used these drugs. Use of stimulants also tends to antedate first use of sedatives and opiates, but not to the same extent that it precedes heroin and cocaine. Some 19 percent of the men who had used both stimulants and sedatives used both for the first time in the same month. The data do not include sufficient detail to determine if the figure of 19 percent represents use of one of these drugs to counteract the effects of the other or reflects a period of intensive experimentation with stimulants and sedatives.

Sedatives were initially used before heroin and cocaine by 63 and 67 percent, respectively, of the men who had used these drugs and sedatives. Neither sedatives nor opiates can easily be classified as antecedent to the other, as 45 percent used sedatives first and 38 percent used opiates before sedatives. For 14 percent of the men who used sedatives and opiates, initial use of both drugs occurred in the same month.

Use of opiates was antecedent to initial use of heroin for 50 percent of the men who had used both drugs, while 19 percent first used these drugs in the same month. Use of opiates was clearly antecedent to cocaine for most of the men who had used both drugs. Figures on the initial use of heroin and cocaine indicate that heroin was more likely to be the first drug used in that pair.

In summary, several findings deserve special attention. First, the data in Table “Number and Percent in Each of Ten Pure Scale Type Patterns of Ever-Never Use” show that the largest number of persons who had used more than one drug had used only alcohol and tobacco; they comprise 33 percent of the total sample. Twenty-two percent of the respondents used only alcohol, tobacco and marihuana. Only 99 (4 percent) of the respondents have used all nine of the drugs studied.

Second, more than 90 percent of the men who had used cocaine, opiates, heroin, sedatives, stimulants or psychedelics had also used marihuana. When users of marihuana are compared with nonusers, higher percentages of the users have used the other drugs.

Third, nine of ten men who had used heroin had also used cocaine, but only 38 percent of the men who had used cocaine had used heroin. This lends support to the idea that heroin signifies the deepest involvement in the drug milieu.

Fourth, in terms of the temporal order of use of pairs of drugs, alcohol was antecedent to use of all the other drugs, including marihuana. For men who have used marihuana and any one of the other drugs, use of marihuana usually occurred first.

Fifth, it was not a rare occurrence for men to begin use of pairs of drugs-psychedelics-stimulants, psychedelics-sedatives, psychedelics-opiates, stimulants-sedatives, sedatives-opiates, heroin-opiates and opiates-cocaine–in the same month.

Finally, it should be repeated that these data do not show that use of any drug causes use of any other drug. However, it is possible that, along with a number of other factors, use of marihuana may have facilitated the movement of persons into use of the other drugs.

 

Selections from the book: “Young Men and Drugs: A Nationwide Survey”. John A. O’Donnell, Ph.D., et al., editors. Report of a national survey of drug use by men 20-30 years old in 1974-1975. National Institute on Drug Abuse Research Monograph 5, February 1976.