Cannabis use is a fact — legal in some places and not in others. Either way, science should be a stronger consideration to inform our policies.
Elsewhere, research has yielded insights that would not have been possible without the ability to study substances in a scientific and controlled setting. Consider that red wine and dark chocolate have properties that are desirable in helping to improve cholesterol, and that cocaine is an excellent topical anesthetic for certain medical procedures.
But what about cannabis (marijuana), a drug gaining in legalization across the U.S. and most recently in Canada? As cannabis develops into a mainstream industry, what has scientific research told us about the risks or benefits of its use?
In the U.S., cannabis remains a Controlled Substances Act Schedule 1 drug like heroin and LSD, which means that it has no currently accepted medical use, has a high potential for abuse, and lacks accepted safety for use under medical supervision. This places extreme limits on scientific research.
Despite being a substance that targets the brain, if and how long-term cannabis use alters brain structure and function remain unknown. There are some known adverse effects. It acutely impairs mental functions and may exacerbate depression, bipolar disorder, anxiety, post-traumatic stress disorder and use of other substances. Whether it is more harmful than substances such as alcohol or nicotine is still undetermined. On the plus side, there is conclusive evidence that cannabis provides relief from symptoms related to chemotherapy and multiple sclerosis. Other potential benefits remain unknown.
So why don't we know more? Because federal policies seemingly put more stock in public opinion than scientific knowledge. This is problematic for three reasons.
Most of what we know (particularly long-term effects) is self-reported by research participants. Even with complete cooperation, one's recollection of their history of cannabis use can have varying degrees of reliability. Self-report also means that scientists cannot verify or quantify factors such as type, potency and quantity of various compounds in cannabis. The opposite is the case regarding alcohol and nicotine, in large part because scientists can accurately measure the quality and quantity of these substances.
As noted by the National Academies of Sciences, U.S. scientists have limited access to cannabis products for research. Regulation barriers mean that only research-graded cannabis produced and supplied by the U.S. government can be used. Thus, science is limited not just by the quantity, but also the quality of cannabis that can be studied. As such, what is being studied in U.S. scientific laboratories is not reflective of current use, medicinally or recreationally.
There are still misconceptions about whether cannabis has any direct influence on criminal activity. The overall weight of the evidence suggests that cannabis use does not cause people to commit more crime. In fact, the one substance that is very much implicated in criminal activity is actually a legal one — alcohol. This is likely because of the culture of the cannabis trade, and because street markets for cannabis are relatively rare. Even further, some research has found that states with legalized medical marijuana have not witnessed an increase in crime rates.
Despite numerous petitions to re-classify cannabis so it is less prohibitive of scientific research, federal policies ignore the need to understand the drug. Hence, scientists and the general public remain in the dark about the real effects of cannabis on the brain, the body, and human behavior.
U.S. science stands to lose ground to others, like Canada, that may grant greater access for research purposes. When it comes to cannabis, a better approach to policy would be from the premise of science.
Francesca M. Filbey is a professor of cognition and neuroscience and associate provost at the University of Texas at Dallas.
Alex R. Piquero is a professor of criminology and associate dean for graduate programs at the University of Texas at Dallas.