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Marihuana, A Signal of Misunderstanding - Table of Contents

The Report of the National Commission on Marihuana and Drug Abuse

Marihuana and (Non-Violent) Crime


The central effort in this report has been to determine whether marijuana use, in and of itself, is meaningfully and causally related to the commission of crime. Two models have been used in the past to answer this issue: the causal model, which holds that using marijuana, being under the influence of the drug, actually does stimulate the will to commit antisocial acts, and the spurious model, which holds that marijuana use is merely a reflection of independent and more powerful forces, and that in itself, marijuana use is unrelated to criminal and aggressive behavior. Some small amount of research has been conducted in the past on this issue, but no consistent findings have been turned up; . . . It is because of these factual lacunae that the National Commission on Marihuana and Drug Abuse mandated a study of marijuana use and crime, which culminated in the Philadelphia survey, as well as this report.

The findings from this study strongly support the view that marijuana, use by itself is not related in any meaningful or systematic fashion to criminal behavior, that marijuana use probably does not "cause criminiality. The "spurious" model appears to be a far more accurate description of the marijuana-crime connection than does the "causal" model. The use of marijuana per se is probably completely unrelated to criminal and aggressive behavior. The drug does not "cause" any significant number of users to commit crimes, or aggressive or violent behavior. The effects of the drug seem to be, from what can be gathered from the available data on the question, without criminogenic causality. This does not mean that it is not possible to commit crimes, including aggressive crimes, under the influence of marijuana-but that being high does not increase one's probability of doing so, that on an hour-for-hour, crime-for-crime basis, there are probably no significant differences between being intoxicated on marijuana and being "normal," not under the influence of any drug.

A wide variety of data have been brought to bear on the marijuana-crime issue.

First of all, regarding the subjective self-reported effects of marijuana, all indications are that the effects classically described as being related to aggressive behavior and the commissions crimes-feeling angry, frustrated, wanting to -hurt someone, being willing to follow any and all suggestions of others, being deranged, wanting to do something violent-have no empirical support whatsoever; users consistently describe these "effects" as non-existent or as extremely rare and atypical, no different from normally. In fact, precisely the opposite is the case: if anything, the effects of marijuana would have far more to do with reducing the criminal "impulse," whatever that might be, due to the fact that they tend to be in the direction of relaxation, feeling calm, of not wanting to move about, feeling somewhat drowsy, sleepy. Activity of any sort tends to be inhibited by the marijuana intoxication.

Secondly, the Philadelphia survey asked the respondents about using marijuana and/or alcohol 24 hours or less before various crimes were committed. Marijuana very rarely figured into the commission of crimes in any way. For only a tiny minority of all crimes committed was the respondent under the influence. This was especially the case for serious and aggressive crimes. Alcohol was far more likely to be used soon before criminal activity than marijuana. -

The third type of information brought to bear on the marijuana-crime question was the self-admitted offense rate of users versus non-users. The total number of different types of crimes which respondents said that they had committed was compared. The simple relationship between using marijuana and committing offenses was positive and statistically significant, and there was also a high correlation between frequency of smoking marijuana and committing offenses. However, a wide range of other variables, themselves related to both crime and to marijuana use, were also correlated-race, education, age, the use of other drugs, and having drug-using friends. Thus, the issue became: is it the causal connection with these third variables which produces the marijuana crime simple correlation, or does the correlation hold up even when these factors are controlled? In other words, which is right, the causal or tile, spurious model? Is marijuana use merely dependent itself on larger, broader, more potent factors-or does it exert an independent power? Do users commit crimes more frequently than nonusers because they use marijuana or because they happen to be the kinds of people who, would have a higher crime rate, marijuana or no marijuana.

The evidence from these three-variable tests support the "spurious" model. The control tables show that the differences in crime rate between users and non-users is, in most cases, dependent not on marijuana use per se, but on these larger factors. The fact that the relationship disappears, or is wiped out, when some controls are applied shows that the marijuana-crime connection is dependent on sociological variables, and not chemical effects. When the use of other drugs was held constant, the marijuana-crime correlation was severely attenuated, and in some cases, washed out entirely. When the variable of having friends who use other drugs-both marijuana as well as stimulants, sedatives, hallucinogens and "hard drugs" was applied, the relationship disappeared among those with drug-using friends, but not those who had no drug-using friends. When race was held constant, the marijuana-crime connection was wiped out completely among whites, but not blacks; among white marijuana users, their crime rate was not statistically different from non-users, but black users did have a higher crime rate than non-using blacks-similar in magnitude to the original relationship. When education was used as a control variable, we saw that among college-educated respondents, the marijuana-crime correlation was nonexistent, but it remained among respondents with a high school education, and for those who had attended graduate school. And lastly, age was applied as a control. Among the youngest groups, the marijuana-crime relationship was attenuated, but it remained somewhat strong among the two oldest age categories.

If there were truly a causal relationship between marijuana use and crime, these disappearing correlations would not occur. The application of sociological variables cannot wash out a chemical reaction in the user. The enormous variability dependent on social factors indicates that marijuana effects do not inherently produce behavior of a criminal nature. The kinds of people who use the drug tend to follow Patterns of behavior regardless of whether or not they use marijuana. By itself, marijuana, use is not a potent producer of behavior, and certainly not criminal behavior. Individuals who commit criminal acts are those who would do so with or without the use of marijuana.

The data from this study support-the conclusion, almost without qualification, that marijuana use does not cause criminal behavior.*

*A subsequent regression analysis with the six variables used independently as controls showed that when all six variables are applied simultaneously, the use of marijuana in and of itself accounts for less than 1% of the variance in committing offenses (personal communication by the author, 24 January 1972).


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