Consequences of Multiple Drug Use: Specifying the Causes


In order to illustrate these points, three specific consequences of drug use will be discussed in some detail below. These three consequences are traffic accidents, involvement in delinquent/criminal acts by youth and young adults, and emergency room visits related to drug abuse.

Traffic Accidents

The Monitoring-the-Future surveys contain several questions concerning traffic accidents. The seniors are first asked how many accidents (i.e., a collision involving property damage or personal injury — not bumps or scratches in parking lots) they had while they were driving in the past 12 months. If the answer is one or more, the senior is asked how many occurred after he/she was drinking alcoholic beverages and then how many occurred after he/she was smoking marijuana or hashish. By piecing together the information from these separate questions, it is possible to estimate the proportion that would be due to alcohol, to marijuana, and to alcohol and marijuana. The data in Table “Motor Vehicle Accidents and Their Connection to Use of Alcohol, Use of Marijuana, and Use of Both Alcohol and Marijuana” are for seniors in the class of 1980 classified according to the extent of alcohol and marijuana use reported during the preceding 12 months (e.g., none, use on less that 40 occasions, and use of 40 or more occasions).

Altogether, 25% or 759 of these 3089 seniors reported having at least one automobile accident during the past 12 months. Some 139 or 18% of the total sample reported the accidents occurred after use of alcohol, marijuana, or both. The largest number was the 75 who reported having an accident after they were drinking. This is only 1.7 times as many as reported an accident occurring after drinking and smoking marijuana (n = 44). These 44 individuals represent automobile accidents related to multiple drug use to traffic accidents among adolescents, it would seem important to differentiate or specify the substances, singular and multiple, that are causally related to the accident.


One of the most widely replicated findings in the drug abuse field is a correlation between involvement in drug use and involvement in delinquent or criminal acts. It is traditional to report the association on a drug-by-drug basis and to emphasize the so-called “criminogenic” potential of drugs such as heroin. However, it is quite possible, given what is known about multiple drug use among addicts, that much of the criminality attributed to the use of “heroin” by addicts is actually a function of chronic heavy use of many drugs, particularly alcohol. The following statement from an intensive study of 61 heroin addicts illustrates this point.

Our findings suggest that alcohol plays an important role in the commission of crime among these heroin abusers; a role much greater than generally believed … These men report a physical and psychological dependence on alcohol as well as on heroin and state that this motivates them to commit crimes… They [the addicts] were more likely to report being under the influence of alcohol when they committed a crime than any other drug.

From a multiple drug use perspective, the important point here is that persons who would traditionally be classified according to the “most serious” drug with which they are over involved are heavily involved on a daily basis with other drugs, particularly alcohol. This finding is replicated in the preliminary findings of a study of arrestees being conducted in Central Harlem. Out of 455 male arrestees who provided urine for testing by EMIT (78% of those eligible), 250 or 55% tested positive within 36 hr after booking for the presence of cocaine, opiates, methadone, and/or PCP. Of the 250 who tested positive for at least one of these drugs, 42% had the metabolites of cocaine in their system. A total of 48 or 19% of those who tested positive had 2 or more drugs present. These data would seem to suggest that multiple drug use is normative among those who have made it into the deepest regions of the drug culture.

The prevalence of multiple drug use among heroin addicts is not a new finding. However, most of the studies in this genre have dealt with heroin addicts. The significance of multiple drug use in relation to involvement in crime would be more apparent if the data were from youth in the “general” population.

Such data exist in the National Youth Survey, a prospective longitudinal study being conducted by Elliott and his colleagues. The sample was drawn initially in late 1976 and consisted of 2360 eligible youth aged 11-17. Of these, 73% or 1725 agreed to participate. The fifth wave of data was collected in 1980 when the respondents were 15-21 and will be used here to illustrate the relationship between multiple drug use and delinquency. The data in Table VIII contain the percent of the sample in each of four developmental “types” or “categories” of drug use. The no use and alcohol use categories do not require comment. The alcohol-marijuana use category invoves use of alcohol and use of marijauna on at least four or more occasions during the preceding year, but no use of other drugs. The multiple illicit drugs category involves use of alcohol, marijuana, and other drugs (amphetamines, barbiturates, hallucinogens, cocaine, or heroin) four or more times each in the preceding 12 months.

Table The Prevalence of Delinquent Behavior by Types of Drug Use among Youth in 1980 (Aged 15-21): National Youth Survey

Delinquent behavior Multiple illicit Alcohol-marijuana Alcohol No drugs
Felony assaults
Percent prevalence 24 14 5 4
Percent of all offenses 47 27 17 9
Felony thefts
Percent prevalence 27 14 4 2
Percent of all offenses 70 21 7 3
Percent prevalence 6 3 * 1
Percent of all offenses 44 16 5 36
Minor assaults
Percent prevalence 30 23 19 17
Percent of all offenses 52 18 16 15
Minor thefts
Percent prevalence 36 23 11 5
Percent of all offenses 49 40 9 3
Illegal services
Percent prevalence 50 19 1 1
Percent of all offenses 94 6 * *
Public disorder
Percent prevalence 88 69 50 16
Percent of all offenses 56 26 16 3
Percent prevalence 31 20 12 10
Percent of all offenses 30 33 21 16

* Less than 0.5%.

Even a brief perusal of the data in Table The Prevalence of Delinquent Behavior by Types of Drug Use among Youth in 1980 (Aged 15-21) reveals a linear type of relationship of drug use type to the prevalence of these types of criminality; the multiple illicit users are more likely than the alcohol-marijuana users to report crimes, and they are more likely than the alcohol or the nonusers to report them. The only exception is for robberies. Another clear finding is that the multiple illicit users, who constitute only 13% of this sample of persons 15-21 years old, account for a disproportionate share of all of the criminal acts reported by the sample. Given the rather crude and conservative criteria for inclusion in the multiple illicit drug user group, the direction and magnitude of these differences are in reported criminality are even more impressive. Simply put, multiple illicit drug use is a rather potent predictor of the probability of invovlement in criminality, even in a sample from the “normal population.”

Emergency Room Episodes

The third area where specification of the causes might help us to better understand the importance of multiple drug use is drug-related emergency room visits. Data from emergency rooms participating in the Drug Abuse conclusion. The data in Table Percent Distribution of Drug Mentions by Number of Other Drugs Used in Combination According to Drug Group show that of 199,093 drug mentions in the 1982 reporting year, only 32.1% involved a single substance. In 38.4% of the emergency room episodes containing a drug mention, one other drug was involved; in 23.1%, two other drugs were mentioned; and in 6.4% of the cases, three or more drugs were involved in the episode. Stated differently, two thirds of the drug-related emergency room episodes in 1982 involved multiple drug abuse.

Table Percent Distribution of Drug Mentions by Number of Other Drugs Used in Combination According to Drug Group

Primary drugs Number of other drugs used in the episode Number of mentions
None One Two Three or more
Tranquilizers 29.9 39.1 24.5 6.6 21,968
Narcotic analgesics 46.7 3019 17.1 5.3 22,503
Nonnarcotic analgesics 39.4 33.0 20.2 7.4 17,557
Nonbarbiturate sedatives 35.5 33.7 25.2 5.5 14,499
Antidepressants 39.8 32.0 21.4 6.8 8,346
Antipsychotics 45.8 29.5 20.0 4.7 8,336
Barbiturate sedatives 25.2 39.2 28.9 6.7 7,256
Amphetamines 35.3 29.6 29.6 5.5 5,081
Hallucinogens 51.4 28.0 16.8 3.6 7,163
Other drugs
Alcohol-in-combination .2 68.9 26.6 4.4 29,348
Cocaine 29.3 40.3 25.7 4.7 6,190
Marijuana 21.5 38.0 36.0 4.5 5,295
All other drugs 30.1 30.7 27.0 12.2 25,906
Total drug mentions 32.1 38.4 23.1 6.4 199,093

At least two findings are of particular importance from the multiple drug use perspective. First, the largest category of drug mentions is the “alcohol-in-combination.” By definition, this category involves multiple drug use. The fact that it is the largest suggests the important role alcohol plays in the lives of Americans who seem to mix it with both licit and illicit drugs, often with serious negative consequences. Second, multiple drug use is quite often found in the mainstream of American society and may be tied, at least in terms of medical consequences, to prescription practices and the availability of over-the-counter (OTC) types of drugs. The basis for this conclusion can be seen in the rows of Table Percent Distribution of Drug Mentions by Number of Other Drugs Used in Combination According to Drug Group that deal with tranquilizers and narcotic and non-narcotic analgesics. These types of drugs used with other drugs account for a large percentage of emergency room episodes each year.

Preliminary Conclusions

There is an understandable tendency in the drug and alcohol fields to be substance specific. After all, our laws and the scheduling of drugs are specific. However, there is substantial and growing evidence that a large minority, perhaps a majority of drug abusers, regularly ingest multiple substances simultaneously in order to enhance the effects of the drugs they are taking, to counteract the effects of one drug with another, or to use one or more drugs as substitute for drugs not available. Simply put, multiple drug use and abuse are a reality that must be recognized and dealt with realistically by anyone and everyone involved in the drug and alcohol field. This will not be easy for researchers and clinicians who have enough difficulty dealing with the use and abuse and measurement of single substances, but we can’t mold reality to fit our wishful perception of reality.

It is time for a rethinking of the way “consequences” of drug abuse have been conceptualized. The automatic attribution of certain consequences/ effects to particular drugs (i.e., traffic accidents to alcohol, overdose deaths to heroin among heroin addicts) will have to be scrutinized by researchers and clinicians. The first step is to begin to untangle the causes of different types of consequences, to sort out which drugs are most often involved in which consequences. The second step is more difficult. It requires an attempt to specify the percentage of variance in the occurrence of various consequences that may be attributed to single drugs and to specific combinations of multiple drugs. Both of these steps require a substantially revised paradigm of the consequences of drug use and abuse, a paradigm that allows for and explicitly takes into consideration the impact of single as well as multiple drug use. It is not possible to untangle and specify the “causes” of consequences until a better understanding of what the consequences are is attained.


Selections from the book: “Recent Developments in Alcoholism. Volume 4: Combined Alcohol and Drug Abuse. Typologies of Alcoholics. The Withdrawal Syndrome. Renal and Electrolyte Consequences.” Edited by Marc Galanter. An Official Publication of the American Medical Society on Alcoholism, the Research Society on Alcoholism, and the National Council on Alcoholism. 1986.