Marijuana Policy Project

Researchers at the Institute for Child Health Policy at the University of Florida College of Medicine examined what effect, if any, medical marijuana laws have on teen use. U.S. anti-drug officials like the drug czar have said such laws decrease the perception of risk and therefore lead to an increase in teen use. Looking at data from 2003-2011 from Montana, Rhode Island, Michigan, and Delaware, these researchers found "no discernible pattern suggesting an effect on either self-reported prevalence or frequency of marijuana use." They conclude that passage of medical marijuana laws does not measurably affect adolescent marijuana use.

Replicating a prior study, but controlling for state characteristics and measurement error, researchers found that medical marijuana laws have little discernible impact on teen marijuana use or perceptions of the risk of marijuana use in those states. In fact, their research showed that passage of medical marijuana laws actually resulted in a slight decrease in teen marijuana use.

Using data from the national and state Youth Risk Behavior Surveys and other government sponsored data collections, researchers from the Universities of Washington, Oregon, and Colorado at Denver found no association between medical marijuana laws and increased teen marijuana use. They concluded, "[o]ur results are not consistent with the hypothesis that legalization leads to increased use of marijuana by teenagers."

Replicating prior published study results that showed higher marijuana use rates in states with medical marijuana laws, researchers examined the link between those laws and teen marijuana use. Results showed that medical marijuana laws "decreased past-month use among adolescents by 0.53 percentage points and had no discernible effect on the perceived riskiness of monthly use," leading the authors to conclude that evidence linking medical marijuana laws to increased teen marijuana use was "limited."

Comparing 101 youths (ages 12-22) with positive symptoms of psychosis to 59 healthy controls of the same age over a period of three years, this study's authors found that, of those clinically predisposed to psychosis, those who used marijuana tended to demonstrate better social functioning. Results also showed that lifetime marijuana use or abuse did not lead to psychosis, even among those youths clinically predisposed to psychosis.

The U.S. has some of the world's most punitive drug policies and also the world's highest rates of marijuana and cocaine use, according to this World Health Organization survey of 17 countries, conducted by some of the world's leading substance abuse researchers.

While federal officials regularly note with alarm that marijuana use is associated with poor grades, this study suggests that poor grades may be a cause of teen marijuana use, not the result. Interestingly, school grades were often a stronger predictor of future marijuana use than were attitudes or beliefs about marijuana.

While federal officials regularly note with alarm that marijuana use is associated with poor grades, this study suggests that poor grades may be a cause of teen marijuana use, not the result. Interestingly, school grades were often a stronger predictor of future marijuana use than were attitudes or beliefs about marijuana.

This biennial Centers for Disease Control survey of U.S. high school students looks at a variety of behaviors that might put young people at risk, including behaviors related to violence, sex, alcohol, and drugs.

Conducted by researchers from the University of Alberta, this ethnographic study of 41 adult Canadian marijuana users found that there is no such thing as a "typical marijuana user."

The U.S. has some of the world's most punitive drug policies and also the world's highest rates of marijuana and cocaine use, according to this World Health Organization survey of 17 countries, conducted by some of the world's leading substance abuse researchers.

What is the real "gateway drug"? This study of twins suggests that use of any drug by young people is an early warning signal that later use of other drugs is likely, with alcohol and cigarettes commonly coming before marijuana or other illicit drugs.

This report -- based on U.S. government data -- details the enormous volume of marijuana harvested and sold untaxed in the U.S., where in 2006 it was the country's number one cash crop, worth more than the corn and wheat crops combined.

With the estimated retail value of the U.S. marijuana market at $113 billion, the local, state, and federal governments are forgoing $31.1 billion in potential sales tax each year. At the same time, marijuana arrests cost taxpayers $10.7 billion annually.

This 60-page report is an evidence-based literature review of marijuana, based only upon research that followed well-accepted research designs, included strong statistical and procedural controls, and passed a careful review by independent scientists.

This British government survey tracks the continuing drop in marijuana use by both adults and teens after Britain ended most marijuana possession arrest in 2004, with marijuana use in the past year reaching its lowest level in more than a decade.

When Britain legally downgraded marijuana in 2004, ending arrests for most marijuana possession cases, critics complained that the move would encourage marijuana use, particularly among young people. This official British government survey -- one of an annual series -- charts a continuing drop in overall drug use, and a significant drop in the use of marijuana, particularly by young people.

In this examination of the gateway theory, researchers studied more than 4,000 Australian twins whose use of marijuana and other drugs was followed in detail from adolescence into adulthood and matched the real-world data from the twins to mathematical models based on 13 different explanations of how use of marijuana and other illicit drugs might be related.