![[Adobe Stock]](https://sp-ao.shortpixel.ai/client/to_webp,q_glossy,ret_img,w_750,h_375/https://www.psypost.org/wp-content/uploads/2025/09/cannabis-thc-cbd-750x375.jpg)
A new study suggests that adding cannabidiol, commonly known as CBD, to products containing caffeine and delta-9-tetrahydrocannabinol (THC) can intensify the drug’s psychoactive effects and increase impairment. The research indicates that while caffeine alone does not substantially alter the body’s processing of THC, the addition of CBD changes how the body metabolizes the intoxicating compound. These findings were published in the journal Neuropsychopharmacology.
The legal landscape for cannabis is shifting rapidly across the United States. State-level legalization and federal provisions such as the 2018 Farm Bill have led to a proliferation of cannabis-derived products. One emerging trend in the commercial marketplace is the sale of beverages that mix cannabinoids with caffeine. These products are often marketed as energy boosters or alternatives to alcoholic drinks.
Despite the growing availability of these mixtures, very little scientific data exists regarding how these chemical constituents interact within the human body. Public health officials and regulators lack precise information on whether combining stimulants like caffeine with depressants or psychoactive compounds like THC creates unique safety risks. Most existing knowledge comes from animal studies, which have suggested that caffeine might worsen memory deficits caused by THC.
To address this gap in knowledge, a team of researchers led by Justin C. Strickland at the Johns Hopkins University School of Medicine conducted a controlled investigation. They sought to evaluate the isolated and combined effects of these substances. The researchers aimed to simulate real-world usage patterns to understand the potential risks facing consumers who purchase these pre-mixed cocktails.
The study recruited twenty healthy adults to participate in the experiment. The group was evenly divided between ten men and ten women. All participants had a history of using cannabis and caffeine, ensuring they were familiar with the substances, but they were not heavy or daily users. This selection criteria helped ensure the results would apply to the general population of casual consumers rather than just chronic users with high tolerance.
The investigation utilized a double-blind, randomized, placebo-controlled crossover design. This means that neither the participants nor the research staff knew which drug combination was being administered during a given session. Additionally, every participant underwent all four experimental conditions at different times. This rigorous structure allowed the researchers to compare an individual’s reaction to the drug mixtures against their own baseline, reducing the influence of personal biological differences.
The four conditions included a placebo session, a session with only THC, a session with THC and caffeine, and a final session combining THC, caffeine, and CBD. The researchers chose to use a cumulative dosing schedule rather than a single large dose. Participants received three separate doses administered over a two-hour period. This method was designed to model how a consumer might slowly drink a cannabis-infused beverage at a social event.
The total dosages administered were 7.5 milligrams of THC, 180 milligrams of caffeine, and 105 milligrams of CBD. These amounts were selected to reflect the potency of products currently available on retail shelves. Throughout the sessions, the researchers collected a wide array of data. They measured subjective feelings, such as how “high” or anxious a participant felt. They also tracked physiological signs like heart rate and blood pressure.
Performance impairment was another key metric. The researchers tested reaction time, memory, and balance. They also utilized a sophisticated driving simulator to assess whether the participants could safely operate a vehicle. Finally, the team collected blood samples to analyze the pharmacokinetics of the drugs. Pharmacokinetics refers to how a drug is absorbed, distributed, metabolized, and excreted by the body.
The results regarding the combination of just THC and caffeine were somewhat unexpected given previous animal models. The researchers found that adding caffeine to THC did not substantially change the subjective experience of being high. Participants did not report feeling more intoxicated, nor did they feel significantly more alert compared to when they took THC alone. The metabolic data confirmed this observation. Caffeine did not alter the concentration of THC in the blood.
However, the team did observe a subtle but potentially risky signal regarding decision-making. When participants consumed the THC and caffeine mixture, they expressed a slightly higher willingness to drive compared to when they consumed THC alone. This increased confidence occurred despite the fact that their actual driving performance on the simulator remained impaired. This disconnect suggests that caffeine might mask feelings of sedation without restoring the physical and mental skills necessary for safety.
The findings shifted dramatically when CBD was introduced to the combination. When participants consumed the mixture of THC, caffeine, and CBD, they reported stronger subjective effects. They felt “higher” and experienced more anxiety than they did with THC alone. Objective tests mirrored these reports. Performance on tasks measuring cognitive and motor skills degraded further in the triple-combination condition.
The blood analysis provided a biological mechanism for these intensified effects. The researchers discovered that the presence of CBD led to higher concentrations of THC in the blood plasma. Additionally, levels of 11-OH-THC were elevated. 11-OH-THC is a potent metabolite produced when the liver breaks down THC. It is known to be more psychoactive than THC itself and readily crosses the blood-brain barrier.
This pharmacokinetic interaction suggests that CBD inhibits the enzymes in the gut or liver that usually break down THC. By slowing this breakdown process, CBD essentially increases the bioavailability of the psychoactive compound. Consequently, a consumer drinking a beverage with both CBD and THC might absorb a higher effective dose of THC than if they had consumed the THC product in isolation.
The study has several implications for consumers and regulators. It challenges the common marketing narrative that CBD is a purely non-intoxicating substance that can “mellow out” the effects of THC. In the context of oral consumption, CBD appears to act as a potentiator. It makes the psychoactive experience stronger and potentially more disorienting.
There are important caveats to consider when interpreting these results. The study focused on a specific ratio of cannabinoids and caffeine. It is possible that different formulations could produce different outcomes. The sample size of twenty people is relatively small, although the within-subject design strengthens the statistical validity. Furthermore, the study only examined oral administration. The metabolic interactions observed here might not occur if the products were inhaled, as smoking or vaping bypasses the digestive system’s first-pass metabolism.
Future research is needed to explore a wider range of doses. Understanding whether lower amounts of CBD still trigger this metabolic interaction is essential. The researchers also highlight the need to investigate other common additives found in these beverages, such as vitamins or taurine. As the market for cannabis beverages expands, more granular data will be necessary to inform safety guidelines.
The authors note that these interactions should be a factor in regulatory decision-making. Current labels often list the milligrams of THC and CBD separately. However, this study indicates that the numbers do not tell the whole story. The biological interaction between the ingredients alters the final effect on the user.
In conclusion, the researchers state regarding the CBD interaction: “The robust alteration of Δ9-THC-induced effects and Δ9-THC pharmacokinetics by CBD further emphasizes the importance of considering full cannabinoid profiles. Broadly, these data highlight the importance of considering drug combinations and interactions in future cannabis regulatory decision-making.”
The study, “Effect of caffeine and cannabidiol (CBD) co-administration on Δ9-tetrahydrocannabinol (Δ9-THC) subjective effects, performance impairment, and pharmacokinetics,” was authored by Justin C. Strickland, Hayleigh E. Tilton, Noah M. Patton, Ryan Vandrey, C. Austin Zamarripa, Tory R. Spindle, Dustin C. Lee, Cecilia L. Bergeria, David Wolinsky, Jost Klawitter, Cristina Sempio, Jorge Campos-Palomino, Uwe Christians, Matthew T. Feldner, Jessica G. Irons and Marcel O. Bonn-Miller.
