"The available evidence suggests that removal of the prohibition against possession itself (decriminalization) does not increase cannabis use. ... This prohibition inflicts harms directly and is costly. Unless it can be shown that the removal of criminal penalties will increase use of other harmful drugs, ... it is difficult to see what society gains."
Findings from dozens of government-commissioned and academic studies published over the past 25 years overwhelmingly affirm that liberalizing marijuana penalties does not lead to an increase in marijuana consumption or affect adolescent attitudes toward drug use.
Since 1973, 21 state legislatures and the District of Columbia have enacted versions of marijuana decriminalization. In each of these states, marijuana users no longer face jail time (nor in most cases, arrest or criminal records) for the possession or use of small amounts of marijuana. Internationally, many states and nations have enacted similar policies.
The following studies examine these decriminalization policies and their impact on marijuana use. The studies' conclusions are listed chronologically.
"In sum, there is little evidence that decriminalization of marijuana use necessarily leads to a substantial increase in marijuana use."
"The Law Revision Commission has examined laws from other states that have reduced penalties for small amounts of marijuana and the impact of those laws in those states. ... Studies of [those] states found (1) expenses for arrest and prosecution of marijuana possession offenses were significantly reduced, (2) any increase in the use of marijuana in those states was less that increased use in those states that did not decrease their penalties and the largest proportionate increase occurred in those states with the most severe penalties, and (3) reducing the penalties for marijuana has virtually no effect on either choice or frequency of the use of alcohol or illegal 'harder' drugs such as cocaine."
"There is no strong evidence that decriminalization affects either the choice or frequency of use of drugs, either legal (alcohol) or illegal (marijuana and cocaine)."
"In contrast with marijuana use, rates of other illicit drug use among ER [emergency room] patients were substantially higher in states that did not decriminalize marijuana use. The lack of decriminalization might have encouraged greater use of drugs that are even more dangerous than marijuana."
"The available evidence indicates that the decriminalization of marijuana possession had little or no impact on rates of use. Although rates of marijuana use increased in those U.S. states [that] reduced maximum penalties for possession to a fine, the prevalence of use increased at similar or higher rates in those states [that] retained more severe penalties. There were also no discernible impacts on the health care systems. On the other hand, the so-called 'decriminalization' measures did result in substantial savings in the criminal justice system."
"Overall, the preponderance of the evidence which we have gathered and examined points to the conclusion that decriminalization has had virtually no effect either on the marijuana use or on related attitudes and beliefs about marijuana use among American young people. The data show no evidence of any increase, relative to the control states, in the proportion of the age group who ever tried marijuana. In fact, both groups of experimental states showed a small, cumulative net decline in annual prevalence after decriminalization."
"Consumption appears to be unaffected, or affected only minimally by decriminalization, and most people believe that it has had little impact. Further, decriminalization has proven to be administratively and economically advantageous for state law enforcement efforts."
"Levels of use tended to be higher in the decriminalization states both before and after the changes in law. [S]tates which moderated penalties after 1974 (essentially a group of decriminalization states) did indeed experience an increase in rates of marijuana use, among both adolescents (age 12-17) and adults (18 or older). However, the increase in marijuana use was even greater in other states and the largest proportionate increase occurred in those states with the most severe penalties."
"The reduction in penalties for possession of marijuana for personal use does not appear to have been a factor in people's decision to use or not use the drug."
"The number of [hospital] admissions directly due to marijuana use decreased from ... 1970 to ... 1975. In the same time, the number of admissions for drug abuse of all types, except alcohol, [also] decreased. ... The following conclusion seem[s] warranted: medically significant problems from the use of marijuana have decreased coincident with decriminalizing marijuana."
"Data collected at four points in time in Ann Arbor [Michigan] and the control communities (which underwent no change in marijuana penalties) indicated that marijuana use was not affected by the change in law [to decriminalization.]"
"The Dutch experience, together with those of a few other countries with more modest policy changes, provides a moderately good empirical case that removal of criminal prohibitions on cannabis possession (decriminalization) will not increase the prevalence of marijuana or any other illicit drug; the argument for decriminalization is thus strong."
"Fear of apprehension, fear of being imprisoned, the cost of cannabis or the difficulty in obtaining cannabis do not appear to exert a strong influence on decisions about cannabis consumption. ... Those factors may limit cannabis use among frequent cannabis users, but there is no evidence, as of yet, to support this conjecture."
"The available data indicate that decriminalization measures substantially reduced enforcement costs, yet had little or no impact on rates of use in the United States. In the South Australian community, none of the studies have found an impact in cannabis use which is attributable to the introduction of the Cannabis Expiation Scheme [decriminalization.]"
"There is no evidence to date that the CEN [decriminalization] system ... Has increased levels of regular cannabis use, or rates of experimentation among young adults. These results are broadly in accord with our earlier analysis of trends in cannabis use in Australia. ...They are also consistent with the results of similar analyses in the United States and the Netherlands."
"The different laws which govern the use and sale of marijuana do not appear to have resulted in substantially different outcomes if we view those outcomes solely in terms of consumption patterns."
"While the Dutch case and other analogies have flaws, they appear to converge in suggesting that reductions in criminal penalties have limited effects on drug use, at least for marijuana."
"General deterrence, or the impact of the threat of legal sanction on the cannabis use of the population at large, has been assessed in large scale surveys. These studies have compared jurisdictions in the USA and Australia where penalties have been reduced with those where they have not, and rates of use have been unaffected. ... Since no deterrent impact was found, this research illustrates a high-cost, low-benefit policy in action. Therefore, if any penalty is awarded, it should be a consistent minimum one. ... The greatest impact on reducing the harmful individual consequences of criminalization would be achieved by eliminating or greatly reducing the numbers of cannabis criminals processed in the first place."
"There does not appear to be a consistent pattern between arrest rates and [marijuana] prevalence rates in the [United States] general population. ... Following precipitous increases, marijuana use began decreasing in the late 1970s, during a period of relative stability in arrest rates. The general deterrence effects of the law (i.e., arrest practices), are not apparent based on the intercorrelations of the measures presented here."
"The evidence is accumulating ... that liberalization does not increase cannabis use [and] that the total prohibition approach is costly [and] ineffective as a general deterrent."
"It has been demonstrated that the more or less free sale of [marijuana] for personal use in the Netherlands has not given rise to levels of use significantly higher than in countries which pursue a highly repressive policy."
"It is clear ... that the introduction of the CEN scheme [decriminalization] in South Australia has not produced a major increase in rates of cannabis use in South Australia by comparison with changes occurring elsewhere in Australia. ... It is not possible to attribute the moderate increases in cannabis use rates in South Australia to the removal of criminal penalties for small-scale cannabis offenses in that state."
"The available evidence suggests that those jurisdictions which have decriminalized personal cannabis use have not experienced any dramatic increase in prevalence of use."
"It appears clear that there is no firm basis for concluding that the introduction of the Cannabis Expiation Notice System in South Australia in 1987 has had any detrimental effect in terms of leading to increased levels of cannabis use in the Southern Australian community. ... In the context of a society which is increasingly well informed about the risks associated with drug use in general, a move toward more lenient laws for small scale cannabis offenses, such as the CEN [decriminalization] system, will not lead to increased cannabis use."