This study explored the acute subjective effects of two cannabis concentrate products, one a THC-dominant concentrate, containing 84.99% total THC and < 1% CBD, and the other, a CBD-dominant concentrate, containing 78.8% total CBD and 4.5% total THC. Expected results were seen in terms of plasma cannabinoid levels in each condition, as well as higher intoxication and drug reward within the THC-dominant condition. Feelings of elation increased significantly in both conditions immediately post-use and declined over the subsequent hour, while tension and anxiety decreased immediately post-use in the CBD-dominant conditions. Anxiety-reduction was also demonstrated in the THC-dominant condition, but with a later onset 1-h after use. Finally, an immediate increase in paranoia was seen in the THC-dominant condition, which began to resolve within the following hour.

Cannabinoid blood levels at the experimental session indicate compliance with assigned treatment group. Specifically, high blood-CBD and low blood-THC immediately post-use in participants in the CBD-dominant group suggests that those individuals used the CBD product, while higher blood-THC and lower blood-CBD levels immediately post-use among those in the THC-dominant group suggest that they used the THC product. The results in the THC-dominant group in the present study are similar to findings from our prior study¹⁸, in which individuals using 70% or 90% THC concentrate products demonstrated somewhat higher THC blood levels immediately post-use (320 ng/mL) compared to immediate-post use plasma-THC in the THC-dominant concentrate group in the present analysis (238.58 ng/mL). However, given that different and more potent products were used in our prior study, some variation in resulting blood levels is expected. It is also notable that in both the current study and in our prior work, cannabinoid blood levels (THC and CBD) peak immediately after cannabis use, but drop considerably one-hour later^18,43. This suggests that across different forms of inhaled cannabis products, regular users experience a significant peak in cannabis blood levels immediately post-use which resolves over the course of the next hour.

In line with the pattern of plasma cannabinoid results noted above, intoxication levels in the present study also increased immediately after concentrate use and decreased over the next hour. Intoxication displayed a significant increase in the CBD-dominant condition, likely due to the fact that there was THC present in the concentrate (although at a relatively low amount). Note that the presence of some THC is typical of CBD concentrate products on the market. Blood data in the CBD-dominant condition showed much lower levels of THC post-use, but the slight acute intoxication effect we observed is still reasonable to expect. Positive mood effects (elation) also significantly increased immediately post-use in both THC and CBD-dominant conditions and decreased significantly one hour later in both groups. Although still above baseline, these scores point to a relatively short-lived mood-enhancing effect of cannabis⁴⁴.

Despite increased positive mood in both groups, the THC-dominant group demonstrated significantly more drug intoxication and rewarding effects (i.e. ARCI, drug liking) immediately post-use compared to the CBD-dominant group. This pattern may be explained by the amount of THC present in the CBD-dominant product being insufficient to produce the euphoric high that regular cannabis users may seek. This coincides with several studies that suggest dose-dependent effects of desirable, euphoric feelings induced by cannabis and THC products^11,12,45,46. Of note, these mood enhancements can be associated with higher risks associated with acute and long-term use, such as impaired judgment and abuse liability.

A difference in groups was also observed in the measure of negative affective states. Specifically, we demonstrated a significant decrease in both anxiety and tension immediately post-use in the CBD-dominant concentrate group which, although qualitatively small, is consistent with the acute anxiolytic effects shown by a number of prior CBD studies^{24,25,47–49}. This finding in conjunction with the existing literature supports the further exploration of hemp-based CBD (ideally taken in a lower-risk form, such as orally) as a potential alternative treatment for acute anxiety, although tightly-controlled human studies in this area are still warranted. In contrast, individuals in the THC-dominant concentrate group did not report significant changes in anxiety or tension immediately post-use, but a significant reduction in anxiety from baseline did emerge at one-hour post-use. This is notable as human studies generally show an anxiogenic acute effect of THC, especially in high concentrations⁵⁰.

However, some subjective data do show a preference for THC or whole cannabis products in the context of self-medicating for affect issues, with few reports of undesirable effects^50,51. Furthermore, anxiogenic effects induced by more typically seen in individuals who fall into the category of infrequent or non-users, rather than those who use cannabis or THC products on a more regular basis^25,50. Importantly, anxiety and tension levels were low overall in the study and do not reflect clinical levels of negative affect. However, findings add to our understanding of the anxiolytic potential of cannabinoids and suggest that additional research is needed to explore the anxiolytic or anxiogenic effects at varying doses, using various THC:CBD ratios, and in among individuals with different types of cannabis use profiles (e.g., regular users, infrequent users, etc.). Future studies should also explore whether adding specific levels of CBD to THC-based concentrates results in a reduction of negative effects in users of such high potency products, as seen in prior studies using different products or methods of administration²⁸.

The THC-dominant group reported significant increases in paranoia immediately post-administration, which resolved one hour later. Acute effects of paranoia following THC use are often noted in subjective outcomes within cannabis studies^11,13,52. However, prior evidence regarding the duration of the effect is lacking. The current study suggests that while paranoia is an undesirable effect, negative effects of THC concentrates such as this are relatively short-lived. It is important to consider this as a dynamic process, and that the duration of positive, negative, and intoxication effects may tend to vary across individuals¹¹.

Finally, in the 5 days prior to the van session, participants’ alcohol and cannabis use patterns were similar across groups and similar to their baseline patterns. These data support the notion that groups were similar on their cannabis use behavior and that participants continued their normal behavior leading up to the experimental appointments, which highlights the naturalistic element of the study design and may serve to bolster generalizability of these findings.

Limitations of the current study include the fact that, due to federal restrictions on legal-market cannabis research, the study design is observational and involves ad libitum administration of cannabis products rather than standardized or controlled cannabis doses. Future studies would also benefit from the use of precise matching of cannabinoid content and a placebo control cannabis product, however such products do not currently exist on the cannabis market. Although future studies would ideally test the acute effects of cannabis concentrates in controlled laboratory settings, tightly-controlled designs such as clinical trials are not currently permitted for these products due to federal restrictions on cannabis research. In addition, we did not collect data on drug expectancies regarding the effects of THC or CBD. Significant data suggests that drug expectancies can impact acute experiences following cannabis use^53,54. Future studies would ideally include a measurement of drug expectancies prior to acute drug administration sessions. Finally, as the CBD-dominant concentrate did contain very low amounts of THC, the effects reported here (e.g. low levels of intoxication and other differences in subjective effects in the CBD-dominant group) may be influenced to some extent by THC present in the product. Despite these limitations, the study also has several notable strengths. In particular, the inclusion of legal-market concentrates, namely CBD-dominant concentrate products, is extremely novel, as these products have not been explored in any laboratory research to date. In addition, our focus on differential effects of THC and CBD may have implications regarding the use of CBD to mitigate harms associated with consumption of THC and/or in users of high THC products more generally. Furthermore, the naturalistic administration aspect of the study provides more generalizable insight into how both THC and CBD may impact individual users in the context of their typical use patterns.

Overall, these results support literature regarding the short-term effects of CBD in reducing anxiety and tension, particularly among users of THC-based cannabis concentrates. Additionally, this research supports existing literature regarding intoxicating and negative psychoactive effects of THC, such as acutely increased paranoia. Ultimately, those in the CBD-dominant condition saw a reduction in tension and anxiety while also experiencing a lower intoxication effect compared to the THC-dominant condition. This pattern may be interpreted as a harm reduction effect of a CBD-dominant cannabis, which was associated with some level of intoxication, but overall decreased negative affect and without the accompanying negative effects of higher levels of THC in our study of regular cannabis concentrate users. These results point to a further need to explore the harm-reducing potential of CBD, which could confer beneficial effects (e.g., on mood and drug reward) to individuals who use high amounts of THC, and perhaps especially for those who use highly potent THC concentrate products.