What is the difference between THCa and CBD?

There are over 400 compounds present in the cannabis plant, with 113 of those being cannabinoids — the active compounds in cannabis. Tetrahydrocannabinolic acid (THCa) and cannabidiol (CBD) are the two most commonly occurring cannabinoids.

Despite both compounds being categorized as cannabinoids, THCa and CBD offer noticeably different effects — especially when THCa is heated and becomes THC, the primary psychoactive cannabinoid known for producing the cannabis “high.”

In this article, we’ll lay the foundation for a comparison of THCa and CBD in terms of their different chemical structures and purported wellness benefits. We’ll also provide a brief overview of the legal status of both compounds — including an examination of the quasi-legal status for THCa embraced by some vendors.

THCa and CBD properties

THCa is the acid analogue of THC, differentiated by the inclusion of a carboxyl group. This is the form of THC found in the raw cannabis plant. When THCa is heated, it undergoes a process called decarboxylation that, as the name implies, removes the carboxyl group and “activates” the THC.

Decarboxylation (“decarbing”) is a key part of cannabis consumption for anyone looking to experience the psychoactive effects of THC. Fortunately for those users, traditional cannabis consumption methods like smoking have the decarb process built in; when you burn and inhale THCa-containing cannabis flower, for example, you’ll be consuming THC instead of THCa.

Decarbing is a key process for activating THC when making edibles as well, and can be done at home with a mason jar and an oven.

Like THC, CBD starts off as an acid (cannabidiolic acid, or CBDa) when it is present in the raw cannabis plant and transforms into its non-acidic state when exposed to heat.

CBD is a non-psychoactive cannabinoid sometimes considered to be a counteragent to THC — the passive, calm “yin” to THC’s active “yang,” as one study characterizes the relationship.

CBD has seen a surge in popularity in recent years, due in part to changes in its legal status that made it possible for growers and processors to sell CBD flower and CBD-rich products.

Wellness benefits of cannabinoids: THCa vs. CBD

While THCa is often sought out by folks intending to decarb THCa to turn it into THC, some studies from the last decade suggest that THCa might offer wellness benefits of its own. 

“Contrary to THC, THCA-A [a sub-type of THCa] does not elicit psychoactive effects in humans and, perhaps for this reason, its pharmacological value is often neglected,” a 2016 literature review states. 

“Despite this perception, many in vitro studies seem to indicate that THCA-A interacts with a number of molecular targets and displays a robust pharmacological profile that includes potential anti-inflammatory, immunomodulatory, neuroprotective, and antineoplastic [i.e., anti-cancer] properties.”

The challenge with THCa is the compound’s instability, according to a 2017 study. Even if THCa isn’t put through an intentional decarb process, it will still turn into THC with exposure to light at room temperature over time. This creates difficulties in both studying and using THCa.

As the 2017 study quotes legendary cannabis researcher Raphael Mechoulam: “How can anybody do an experiment if the compound likes to convert into something else just by sitting around, and the ‘something else’ has all kinds of activities?”

Like THCa and THC, CBD offers a variety of recorded wellness benefits in both its acid and non-acid forms.

CBDa has been reported to provide relief from nausea and vomiting, seizures, and anxiety. Studies have also shown that CBDa might help prevent the growth and spread of breast cancer cells and suggested that CBDa might hold potential as an alternative to SSRIs when treating depression. 

CBD, in its non-acid form, has been reported to “produce a wide range of pharmacological activity including anticonvulsive, antiinflammatory, antioxidant, and antipsychotic effects.”

Check out the differences between CBD and THC from Jointly to learn more.

Is THCa legal? Is CBD legal?

The legal status of the cannabis plant — either in its THC-rich chemotype or non-THC “hemp” chemotype — was drastically impacted in 2018 by the Agricultural Improvement Act, also referred to as the 2018 Farm Bill. 

This legislation, in a broad sense, allows for the growth and sale of hemp — cannabis plants containing less than 0.3% delta-9-THC by dry weight. Hemp plants tend to be rich in CBD, and hemp growers and processors have benefitted from a boom in interest in the potential wellness-supporting benefits of CBD.

Still, the regulatory status of any product derived from the cannabis plant remains somewhat murky.

In the case of CBD, there is still a lack of government oversight designed to ensure that only high-quality, accurately-labeled products make it to market.

In the meantime, at least one study has shown that the CBD products available to consumers today can have as much as 10% more or less CBD than stated on the label. Some CBD products have even been found to contain THC, meaning that consumers might unwittingly consume THC — a potential disaster for anyone who needs to pass a drug test.

Things get even more complicated for THCa, which has also enjoyed a thriving quasi-legal market where vendors offer “a general declarative statement indicating that their products are hemp as defined under federal law,” according to a 2022 report from the National Institute of Justice.

As you might guess based on our discussion of decarboxylation earlier in this post, that purportedly legal THCa becomes THC when heated — making the end result of consumption via, for example, smoking, essentially indistinguishable from that of regular THC.

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