Breaking Down Popular Cannabis Compounds

The US Cannabis Landscape 

Marijuana use in the U.S. is at an all-time high, with 46.9% of Americans aged 12 or older reporting having tried marijuana at least once, and 15% reporting having used it in the past 30 days. Various factors contribute to this rise in use, including:

• Greater availability.
• Declines in perceived harm.
• Desires for alternatives to alcohol and pharmaceutical drug therapies.

However, while cannabis use is increasingly normalized, the legal landscape surrounding the popular plant is more complicated than ever. Discrepancies in federal and state laws are one source of tension, as marijuana is now legal in some form in 38 states but remains illegal at the federal level. In 2018, Congress added another twist by legalizing hemp. Hemp, known for its industrial applications, is very similar to marijuana except for one key difference: It has lower concentrations of delta-9 tetrahydrocannabinol (THC), a substance with psychoactive properties.

Most elected officials likely did not anticipate that legalizing hemp would pave the way for an impairing substance, but due to loopholes in federal and state laws, that is exactly what has happened. While policymakers have focused on delta-9 THC — the most well-known impairing compound in the cannabis plant — cannabis producers and manufacturers have developed methods to produce other substances with effects similar to delta-9 THC but with less legal baggage.

This brief provides an overview of several popular cannabinoids to help readers understand the complexities of the cannabis marketplace. It also serves as background for a forthcoming report detailing current state laws on hemp, potential health risks of poorly regulated products, and recommendations for improving oversight of cannabinoid markets. 

Cannabis Compounds Explained

Cannabis: A generic term that refers to all parts and products of the Cannabis sativa L. plant. In legal terms, cannabis is referred to as hemp or marijuana according to its THC level.

Hemp: Cannabis sativa defined in U.S. law as having a concentration of less than 0.3% delta-9 THC by dry weight. Hemp is federally legal and regulated under civil agriculture and health department laws.

Marijuana: Cannabis sativa defined in U.S. law as having a concentration of delta-9 THC greater than 0.3% by dry weight. Marijuana is federally illegal with criminal enforcement under the Controlled Substances Act.

Delta-9 Tetrahydrocannabinol (THC): Delta-9 THC is the primary psychoactive compound in cannabis responsible for the so-called high feeling typically associated with marijuana use. It is the most extensively researched cannabis compound, present in both hemp and marijuana plants, which are distinguished by their levels of delta-9 THC. Cannabis plants with less than 0.3% delta-9 THC by dry weight are hemp, while those with delta-9 THC in quantities above this threshold are marijuana. Hemp is federally legal, and marijuana is not.

Cannabidiol (CBD): CBD is a non-impairing cannabinoid that is naturally present in both hemp and marijuana. Unlike delta-9 and other THC isomers, CBD does not produce impairing effects. It is widely regarded for its potential benefits in reducing anxiety, alleviating pain, and managing inflammation. Under the 2018 Farm Bill, hemp-derived CBD is legal at the federal level as long as it contains no more than 0.3% delta-9 THC. CBD products can come in many forms, including oils, tinctures, edibles, and topicals. The popularity of CBD has also led to its proliferation in consumer goods, from skincare to beverages to pet treats. However, in January 2023, the Food and Drug Administration concluded that it cannot regulate CBD products within existing frameworks; thus, the future of this market remains uncertain.

Delta-8 THC: Delta-8 THC is naturally occurring in the cannabis plant and has effects that are reportedly milder than those of delta-9 THC. Delta-8 exists naturally in concentrations of 0.1% or less, an amount too small to appeal to most consumers. To achieve greater volume (15–20%), CBD is converted into delta-8 THC using an organic solvent and an acid. There are numerous methods for synthesis, many of which can produce byproducts that are not safe to consume. While delta-8 THC derived from hemp is widely considered legal under the 2018 Farm Bill, delta-8 THC derived from marijuana is included in the Drug Enforcement Administration’s (DEA) Controlled Substances list and is illegal. Most delta-8 THC sold in consumer products is derived from CBD in hemp. In fact, a market surplus of hemp-derived CBD is at least partially responsible for the delta-8 boom. However, some delta-8 THC products are made with the waste from marijuana plants, and as such are not legally compliant in states where marijuana is prohibited.

Hexahydrocannabinol (HHC): HHC is a hydrogenated semisynthetic form of THC with similar effects and potency. Put another way, HHC is to THC what margarine is to butter. HHC is made by saturating the THC molecule with hydrogen, which causes all of THC’s double bonds to break and be replaced with hydrogen. This results in a more stable form of THC with a longer shelf life, as it is less susceptible to oxidation and breakdown. By contrast, delta-9 THC loses potency over time because it oxidizes and loses hydrogen atoms. The effects of HHC are reportedly between those of delta-8 and delta-9 THC, but these can vary widely depending on how the cannabinoid is synthesized. Many state laws treat HHC as a legal derivative of hemp, though the DEA has stated that it does not consider HHC to be naturally occurring in the cannabis plant.

THC Acetate Ester (THC-O): THC-O is a THC analog. It is made by adding an acid compound, such as acetic anhydride, to delta-8 or delta-9 THC. Its potency is not fully known, though some experts estimate that it could be two to three times stronger than delta-9 THC. In a letter from February 2023, the DEA stated that THC-O is illegal because it is not naturally occurring in the cannabis plant. This stance was rejected by the 4th Circuit Court of Appeals, which ruled on Sept. 4, 2024, that THC-O is legal under the 2018 Farm Bill definition of hemp. The court concluded that since THC-O can be synthesized from THC, it is therefore a hemp “derivative” as defined by the 2018 Farm Bill. In the 4th Circuit Court’s opinion, as long as delta-9 THC concentration does not exceed 0.3% by weight, THC-O is federally legal.

Tetrahydrocannabinolic Acid (THCa): THCa is a naturally occurring compound in both hemp and marijuana plants. It is not intoxicating, until it is heated. Once heated, THCa converts into delta-9 THC. The 2018 Farm Bill says that tests to determine whether a substance is hemp must account for both delta-9 THC and THCa content, the sum of which is not to exceed 0.3% concentration by weight. The DEA has interpreted this to mean that products with THCa in concentrations greater than 0.3% do not constitute hemp and are therefore illegal.

But some hemp legal experts argue that a straightforward reading of the 2018 Farm Bill applies the THCa testing requirement solely to producers, mandating them to test their product preharvest. According to this line of reasoning, the post-harvested hemp material used in consumable products can have any amount of THCa as long as it does not exceed the 0.3% delta-9 THC threshold. Many state hemp laws do not specifically require THCa testing, widening the loophole to sell products high in THCa. While cultivating hemp with less than 0.3% delta-9 THC and higher levels of THCa may be possible, most products labeled as high-THCa hemp contain delta-9 in amounts above the legal threshold.

Adding another layer to this issue, many state crime labs test THC products differently from the labs that test and certify products for the hemp industry. Industry labs typically use high-pressure liquid chromatography, a method that differentiates between THC and THCa. This results in products with certificates of analysis that show low levels of delta-9 THC and high levels of THCa. However, state crime labs test THC products using gas chromatography. This method involves applying heat to the sample, which converts THCa into delta-9 THC. A product that shows low levels of delta-9 THC and high levels of THCa using the liquid method would show high levels of total THC using the gas method and therefore would be considered illegal federally and in states that have not legalized marijuana.

Marijuana’s Potential Federal Reclassification

Marijuana remains a Schedule I drug under the Controlled Substance Act, alongside heroin, lysergic acid diethylamide (LSD), phencyclidine (PCP), and crack cocaine. Schedule I substances are those deemed to have high potential for abuse and no medical value. Reflecting notable developments in research and practice, the Department of Health and Human Services (HHS) recommended in August 2023 that marijuana be moved to Schedule III, a category for substances that have a moderate to low potential for physical and psychological dependence. In its recommendation, HHS cited evidence for marijuana’s efficacy in treating pain, cancer-related nausea, and anorexia.

In May 2024, the DEA announced a proposal to reclassify marijuana as a Schedule III substance. On Dec. 2, 2024, the agency will hold an administrative hearing on the marijuana rescheduling proposal. Once the agency reviews the judge’s report and responds to critical issues submitted during the public comment period, the DEA can publish its final rulemaking in the Federal Register. This process can take several months or years to complete and be delayed further by legal challenges.

Separate from these federal developments, marijuana is legal for medical use in 38 states and for adult recreational use in 24 states and the District of Columbia. Most of these states permit the sale of marijuana flower and a variety of delta-9 THC products, including tinctures, beverages, edibles, vapes, and concentrates. Potency can range from as little as less than 1 milligram (mg) of THC in a package to upward of 750mg, though all states with established retail markets have imposed limits on how much THC a single serving of an edible product can contain. In most states where marijuana is prohibited, hemp-derived delta-9 THC is available in concentrations of less than 0.3% by dry weight, but some states have imposed additional restrictions.

For more information on the legal status of impairing hemp products across the U.S., see the Drug Policy Program’s interactive map here.

Looking Ahead

The complexities of the cannabis plant and the ongoing legal battles surrounding it underscore the challenges of crafting clear regulatory guidelines. A forthcoming report from the Drug Policy Program discusses:

• The shifting legal status of hemp.
• Health risks posed to consumers due to insufficient oversight.
• Recommendations for improving current regulatory practices.

The forthcoming report will be made accessible here upon publication. 

This material may be quoted or reproduced without prior permission, provided appropriate credit is given to the author and Rice University’s Baker Institute for Public Policy. The views expressed herein are those of the individual author(s), and do not necessarily represent the views of Rice University’s Baker Institute for Public Policy.