The significant role of the law enforcement community and the popular press in promoting the idea that marihuana use leads to undesirable and antisocial behavior has been discussed in the Report. The purpose of this chapter is to describe the genesis of the, perceived problem and the theoretical basis for these allegations.

The early campaigns against marihuana use can be viewed as an extension of the temperance and moral reform movements which swept the country during the 1920's. They were generally spearheaded by persons who opposed the use of opiates, alcohol and tobacco on the grounds that all such substances were physically, mentally and morally debilitating. The presumed dependence of the user on the drug, the loss of self-control and the unhealthy preoccupation with pleasure-seeking activities purportedly induced by these substances were seen as contrary to the traditional values of our society.

Reiteration of these themes by practicing professionals, respected members of officialdom and the popular press ultimately gave rise, to what Lindesmith (rev. ed., 1968: 188-189) has termed the "evil causes evil" fallacy, and which Goode (1972) has de-scribed as follows:

The impetus behind public and even expert conceptions of drugs and drug use is that a phenomenon so patently undesirable and universally condemned as the use of narcotics or marihuana must, inevitably, have both pathological causes as well as pathological consequences. Thus, the task of science and medical research is seen as "discovering" these negative concomitants of illicit drug use. In this way, we can all feel better about condemning the phenomenon itself because our moral and ideological feelings can thereby be, backed up and verified by the Indisputable data of positive science (p. 1).

This same philosophical leaning of persons who view marihuana as a significant danger to both the individual and society carries with it a corollary that use be prohibited and the user punished.

Perhaps the most persistent controversy with respect to marihuana use is the degree to which it poses a danger to public safety. Public and professional opinion surveys have repeatedly demonstrated the existence of a widespread belief that marihuana use leads to the commission of deviant, delinquent, criminal and violent acts. In addition, some persons have recently expressed concern that marihuana impairs driving skills and performance and, in this way, also constitutes a public safety hazards.

This chapter will review the evidence pertaining to the effects of marihuana on criminal and violent behavior, deviant and aggressive sexual behavior and driving skills and performance. Then an effort will be made to assess both the nature and strength of the purported relationships between marihuana use and these behaviors.

Problems in Assessing the Effects of Marihuana

The degree to which marihuana constitutes a danger to public safety is dependent, in large measure, upon the drug's observable, effects on the behavior of the user. No drug, including marihuana, produces the same effect at all times, under all conditions and in all individuals. Rather, the quality (form and intensity) and the quantity (extent and frequency) of the perceived effects are determined by the complex interaction of both pharmacological and extrapharmacological factors. As Goode (1972) has noted:

We should bear this qualification in mind when looking at the relationship between the ingestion of a drug and any subsequent behavior-with the latter supposedly "caused" by the effects of the drug. Drug effects vary, and, in addition, even standard effects do not automatically translate into specific forms of human behavior (P. 18).

In a paper prepared for the Commission, Tinklenberg (1971 : 1-8) has enumerated some of the basic factors which should be taken into consideration in evaluating the relationship between marihuana and crime. They are equally relevant, however, for the assessment of any behavioral effect presumably attributable to marihuana, and for that reason they are summarized below.

Definition and Congeners. The concentration of the principal active chemicals in cannabis (THC and their metabolites) in any given amount of marihuana varies widely according to where the plant is grown, how it is cultivated, harvested and cured. These variations permit a wide range of pharmacological potencies and unknown variations in their effects on behavior.

Drug-Drug Interactions. Given the strong possibility of intentional or inadvertent adulteration of marihuana with other psychoactive drugs, it may be that behavioral changes attributed to marihuana may actually derive from the adulterants or from the interaction of THC and the adulterants (which may well be occasioned by the deliberate rather than unknown simultaneous or sequential use, of other psychoactive drugs).

Dose-Response Functions. With respect to the question of how drugs affect behavior, it is likely that marihuana influences behavior in different ways and degrees, depending upon dosage levels. Although it is common to infer that higher doses of a given drug will induce more of a particular response and lower doses less, such inferences may be inaccurate in that drug effects can show a curvilinear dose-response relationship (as seems to be the case with alcohol).

Time-Action Functions. Time-action function describes the changing effects of marihuana during the course of the drug action. During the brief periods in which the drug effects are most intense, there may be a more pronounced alteration in behavior than during most of the points on the drug time-action continuum.

Individual Variation. Different individuals apparently respond quite differently to the same dose-time factors of marihuana as well as other drugs. In some laboratory studies, where, high doses of marihuana induced considerable euphoria and enhanced conviviality in most subjects, a few subjects who received the same dosage in the same setting experienced paranoia, excessive agitation and aggressive tendencies.

Cumulative Effects. The effects of marihuana on individual behavior have been shown to vary according to the amount of previous experience with the drug. There is increasing evidence that chronic users respond quite differently to marihuana than do occasional users. The cumulative extent of previous experience may have an important influence on subsequent behavioral responses.

Psychological and Environmental Variables. The behavioral response to marihuana and to other drugs is at least partially dependent upon such psychosocial variables as the expectations of the user regarding its influence on his behavior. These expectations are in turn derived from. the personalities of the, individuals involved, recent events in their lives, and the physical, interpersonal and social milieu in which the marihuana use occurs. The behavioral responses to marihuana use are likely to correlate with such psychological and environmental variables quite independently of any pharmacological effects the drug may exert.

Personality Factors. A certain number of individuals in any given population demonstrate characteristic and relatively enduring patterns of antisocial behavior regardless of their immediate circumstances, possible drug use and the like. These individuals, variously described as antisocial, criminal or emotionally unstable, typically manifest, from childhood on, recurrent tendencies toward deviance in many areas of life. For some of these people, those predisposed toward both criminality and drug abuse, crime and drug use do coexist. However, the assumption that the drug causes crime or vice versa is not necessarily valid. One should not automatically conclude from this that the use of drugs has no influence on their criminal behavior. Drug use may possibly provide a form of reinforcement which may increase or decrease the likelihood of a criminal act.

Crime Process Factors. Crime process factors refer to the complexities of criminal behavior and the possible influence of marihuana on that behavior. A multifactored perspective of the etiology of crime , including personal, social and situational variables, allows for the possibility that at each step in the chain of events leading to the commission of a criminal act, marihuana use may contribute to enhance or diminish the possibility of this outcome.

In short, any interpretation of the data to be presented below which fails to take into account at least some of these variables will likely result in a "post hoc, ergo propter hoc" fallacy-that is, the invalid assumption that simply because one event occurs later than another event (one commits a crime after smoking marihuana) that the latter is caused by the former (marihuana caused the crime).