Controlled substances fall into five categories determined by three criteria: abuse potential, safety and medical value. Schedule I, the most restricted category, is reserved for highly addictive drugs that lack medical value and any level of safe use, even under medical supervision. Substances in this category, which are illegal in all instances, include the following: heroin, khat, ayahuasca, GHB, lysergic acid diethylamide (LSD), mushrooms, etorphine (an opioid 3,000 times stronger than morphine used to immobilize elephants), MDMA (ecstasy), mescaline, peyote and cannabis in all its forms, including hemp and non-psychoactive cannabinoids like cannabidiol (CBD).
Schedule II is the most-restricted substance still available via a doctor’s prescription. These drugs are viewed as addictive and dangerous, but they have medical value, and safe use is possible under a doctor’s supervision. Examples include cocaine, crystal meth, amphetamines, oxycodone (OxyContin, Percocet), hydrocodone (Vicodin), morphine, opium and methylphenidate (Ritalin). The remaining three classifications are viewed as progressively less addictive and dangerous. These more readily available drugs include Schedule III substances like steroids, ketamine and buprenorphine; Schedule IV substances like benzodiazepine (Xanax, Valium, Klonopin) and so-called Z-drugs like zolpidem (Ambien) and eszopiclone (Lunesta); and Schedule V drugs like certain cough suppressants (with minor amounts of codeine) and diarrhea medications (which some people inexplicably inject like heroin). Furthermore, Congress specifically excluded alcohol and tobacco products from scheduling in 1970.
In 2016, a Vox/Morning Consult poll found that 82 percent of Americans did not realize cannabis was a Schedule I substance. In guessing its classification, respondents most commonly assumed the plant was a Schedule IV or V substance. Furthermore, the poll asked where cannabis should be classified, and the most common answer was that cannabis should be removed from the Schedules altogether.