Partygoers dance and smoke pot during the annual 4/20 marijuana festival in Denver (AP Photo/Brennan Linsley)

Through federal court challenges and Congressional initiatives, activists have been pushing hard to have marijuana removed from Schedule I of the Controlled Substances Act. Marijuana sits with heroin on the highly restrictive Schedule I, while cocaine and methamphetamine are on the less restrictive Schedule II. This leaves many people puzzled: How can the federal government claim that pot is as dangerous as heroin and more dangerous than meth?

In reality, that isn’t what the Schedule I status of marijuana means, but the odds are long against this ever being widely understood by policymakers or the public. The interpretive problem comes about because the CSA tries to capture in a single number two variables that aren’t necessarily connected: Medical value and dangerousness.

The CSA rates drugs on scale, creating a scheduling system that runs from I to V. In general, the higher the number of the schedule, the less dangerous a drug is considered to be, and thus controls on it are weaker (i.e., It’s easier to obtain and refill prescriptions). For example, Robitussin AC cough syrup, which contains a small amount of codeine, is on Schedule V, whereas the more potent and dangerous opioid fentanyl is on Schedule II.

But another factor comes into play in differentiating Schedules I and II: to be Schedule II a drug has to be approved for medical use by the Food and Drug Administration (FDA). Cocaine for example goes on Schedule II because it has been approved as a topical anesthetic in certain surgical procedures.

Marijuana in contrast can’t become FDA approved because unlike cocaine it is raw plant matter of complex and varying composition. A standardized, pure component of marijuana – for example the synthetic tetrahydrocannabiol found in the Schedule III medication dronabinol – can escape schedule I by going through the FDA process. In contrast, the plant itself, not being suited to the FDA approval system, ends up on a more restrictive schedule than cocaine, which kills over 4,000 Americans a year.

The implicit assumption of the scheduling system is that not being medically useful gives some drugs an extra “oomph” of dangerousness that pushes them into Schedule I, the worst of the worst. This would make sense if medical value and dangerousness were the opposing ends of the same dimension, but they are not. Prescription opioids are highly effective for easing the pain of cancer patients, yet also kill more Americans each year than all Schedule I drugs combined. Similarly, drug policy expert Mark Kleiman of New York University’s Marron Institute argues that the current scheduling system “has no logical place for drugs like psilocybin mushrooms that have no recognized medical use, but not much abuse potential either”.

Kleiman favors a simplified scheduling system that focus only on a drug’s potential for abuse. “Medical utility is simply a different question”, he points out.

At a minimum, such a system might be easier for the public and policymakers to understand. Psychological research indicates that human beings are prone to global, emotionally simple judgements of risk, i.e., we want to think of a drug as either harmful or beneficial, not as harmful in some ways and dangerous in others. The current scheduling system accentuates the human tendency to oversimplify, and thus prevents us from grappling honestly with the fact that sometimes the most dangerous and most medically useful drugs are one and the same.

Keith Humphreys is a Professor of Psychiatry and Director of Mental Health Policy at Stanford University.