Preliminary study of the interactive effects of THC and ethanol on self-reported ability and simulated driving, subjective effects, and cardiovascular responses

A randomized, placebo-controlled, double-blind, pilot study of cannabis-related driving impairment assessed by driving simulator and self-report

AIMS

In the context of increasing cannabis use, understanding how cannabis affects specific driving behaviors is crucial in mitigating risks and ensuring road safety.

DESIGN AND SETTING

The current study included 38 adults aged 18-40 years, administered a single 0.5 g acute dose of vaporized cannabis (5.9% Tetrahydrocannabinol (THC), 13% THC or placebo) in a randomized, within-subject, double-blind, counterbalanced design. Throughout each of the three, 8-h assessment days, at 4 time points, participants underwent simulated driving tests, including lane-keeping, car following, and overtaking tasks, capturing 19 behavioral metrics. An SPSS linear mixed model assessed the main effects of dose, time, and dose × time.

FINDINGS

During lane-keeping, participants exhibited reduced steering reversal rates up to 5.5 h following 13% THC and 3.5 h for 5.9%. For car following, participants showed reduced pedal peak-to-peak deviation and reversal rates, persisting for 1-3 h post-dose (only at 13% THC). During overtaking, following 13% THC, subjects demonstrated a shorter median gap to passed cars, lower time-to-potential collision, and more time in the oncoming lane. Drug effects on driving metrics improved gradually, to varying degrees over time. Approximately 66% of participants reported willingness to drive, despite subjective awareness of being impaired and objectively worse driving performance.

CONCLUSIONS

Our study reveals for the first time long-lasting cannabis-induced impairments across multiple driving behaviors, that extend beyond the typical 3-h window explored in most previous research. The observed discrepancy between participants' willingness to drive and their actual impairment highlights an important public safety concern. In addition, the lack of correlation between cannabinoid metabolite concentrations and driving performance challenges the reliability of blood THC levels as impairment indicators, emphasizing the need for a multifaceted approach to assessing cannabis-impaired driving risk.

Young Age and Concomitant Cannabis (THC) and Ethanol (EtOH) Exposure Enhances Rat Brain Damage Through Decreased Cerebral Mitochondrial Respiration

The reason why young people taking concomitantly cannabis (THC) and ethanol (EtOH) are more prone to stroke is underresearched. To investigate whether an underlying mechanism of increased brain damage could be an impaired mitochondrial function, this experiment determined the acute effects of EtOH, both alone and associated with THC, on mitochondrial respiration and oxidative stress (hydrogen peroxide H2O2) on young (11 weeks) and middle-aged (45 weeks) brain in rats, using a high-resolution oxygraph (Oxygraph-2K, Oroboros instruments). In young brains, EtOH decreased mitochondrial respiration by -51.76 ± 2.60% (from 32.76 ± 3.82 to 17.41 ± 1.42 pmol/s/mL, p < 0.0001). In 45-week-old brains, the decrease was lesser, but still significant -36.0 ± 2.80% (from 30.73 ± 7.72 to 20.59 ± 5.48 pmol/s/mL, p < 0.0001). Concomitant THC aggravated brain mitochondrial respiration decreases at 11 weeks (-86.86 ± 1.74%, p < 0.0001) and at 45 weeks (-73.95 ± 3.69%, p < 0.0001). Such additional injury was enhanced in young brains (p < 0.01). H2O2 production was similar in both age groups (1.0 ± 0.2 versus 1.1 ± 0.08 pmol O2/s/mL) and was not modified by THC addition. In conclusion, EtOH alone significantly impairs brain mitochondrial respiration and concomitant THC further aggravates such damage, particularly in young brains. These data support the hypothesis that enhanced mitochondrial dysfunction might participate in the increased occurrence of stroke in the young and urge for better prevention against EtOH and THC addictions in adolescents.

Cannabis (THC) Aggravates the Deleterious Effects of Alcohol (EtOH) on Skeletal Muscles' Mitochondrial Respiration: Modulation by Age and Metabolic Phenotypes

The anti-inflammatory and analgesic properties of cannabis might be useful to treat muscle diseases, including those linked or not to alcohol. Nevertheless, delta 9 tetrahydrocannabinol (THC) and ethanol (EtOH), often used concomitantly, can have deleterious effects on cardiac mitochondria. We therefore determined whether EtOH, alone and associated with THC, impairs skeletal muscle mitochondrial respiration. Further, we investigated potential modulation by metabolic phenotype and age by analyzing predominantly glycolytic gastrocnemius and oxidative soleus muscles in young and middle-aged rats (12 and 49 weeks). Considering the gastrocnemius, EtOH impaired mitochondrial respiration in a similar manner in young- and middle-aged muscles (-34.97 ± 2.97% vs. -37.50 ± 6.03% at 2.1 × 10-5 M; p < 0.05). Interestingly, concomitant THC aggravated EtOH-related mitochondrial impairment in young gastrocnemius (-49.92 ± 1.69%, vs. -34.97 ± 2.97 p < 0.05). Concerning the soleus, EtOH alone mainly decreased young muscle mitochondrial respiration (-42.39 ± 2.42% vs. -17.09 ± 7.61% at 2.1 × 10-5 M, p < 0.001, at 12 and 49 weeks). The soleus was less impaired at 12 weeks by THC and EtOH association than the gastrocnemius (-49.92 ±1.69 vs. -27.22 ± 8.96% in gastrocnemius and soleus, respectively, p < 0.05). In conclusion, EtOH, alone and associated with THC, significantly impairs skeletal muscle mitochondrial respiration and THC aggravates EtOH-induced effects on young glycolytic muscle. Age and metabolic phenotypes modulate these deleterious effects, with the glycolytic muscles of young rats being more prone to impairments than oxidative muscles.

Evaluating possible 'next day' impairment in insomnia patients administered an oral medicinal cannabis product by night: a pilot randomized controlled trial

Cannabis and its major constituents, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), are being widely used to treat sleep disturbances. However, THC can cause acute cognitive and psychomotor impairment and there are concerns that driving and workplace safety might be compromised the day after evening use. Here, we examined possible 'next day' impairment following evening administration of a typical medicinal cannabis oil in adults with insomnia disorder, compared to matched placebo. This paper describes the secondary outcomes of a larger study investigating the effects of THC/CBD on insomnia disorder. Twenty adults [16 female; mean (SD) age, 46.1 (8.6) y] with physician-diagnosed insomnia who infrequently use cannabis completed two 24 h in-laboratory visits involving acute oral administration of combined 10 mg THC and 200 mg CBD ('THC/CBD') or placebo in a randomised, double-blind, crossover trial design. Outcome measures included 'next day' (≥9 h post-treatment) performance on cognitive and psychomotor function tasks, simulated driving performance, subjective drug effects, and mood. We found no differences in 'next day' performance on 27 out of 28 tests of cognitive and psychomotor function and simulated driving performance relative to placebo. THC/CBD produced a small decrease (-1.4%, p=.016, d=-0.6) in accuracy on the Stroop-Colour Task (easy/congruent) but not the Stroop-Word Task (hard/incongruent). THC/CBD also produced a small increase (+8.6, p=.042, d=0.3) in self-ratings of Sedated at 10 h post-treatment, but with no accompanying changes in subjective ratings of Alert or Sleepy (p's>0.05). In conclusion, we found a lack of notable 'next day' impairment to cognitive and psychomotor function and simulated driving performance following evening use of 10 mg oral THC, in combination with 200 mg CBD, in an insomnia population who infrequently use cannabis.

The effects of simultaneous alcohol and cannabis use on subjective drug effects: A narrative review across methodologies

Over 75% of young adults who use cannabis also report drinking alcohol, leading to increased risks that include impaired cognition, substance use disorders, and more heavy and frequent substance use. Studies suggest that subjective responses to either alcohol or cannabis can serve as a valuable indicator for identifying individuals at risk of prolonged substance use and use disorder. While laboratory studies show additive effects when alcohol and cannabis are used together, the impact of co-using these substances, specifically with respect to cannabidiol, on an individual's subjective experience remains unclear. This narrative review explores the effects of simultaneous alcohol and cannabis (SAM) use on subjective drug effects, drawing from qualitative research, laboratory experiments, and naturalistic studies. Experimental findings are inconsistent regarding the combined effects of alcohol and cannabis, likely influenced by factors such as dosage, method of administration, and individual substance use histories. Similarly, findings from qualitative and naturalistic studies are mixed regarding subjective drug effects following SAM use. These discrepancies may be due to recall biases, variations in assessment methods, and the measurement in real-world contexts of patterns of SAM use and related experiences. Overall, this narrative review highlights the need for more comprehensive research to understand more fully subjective drug effects of SAM use in diverse populations and settings, emphasizing the importance of frequent and nuanced assessment of SAM use and subjective responses in naturalistic settings.

Driving Under the Influence of Alcohol, Cannabis, and Delta-8 THC: Perceived Likelihood, Risk Perceptions, and Behaviors

Driving under the influence (DUI) of alcohol or cannabis poses public health risks. Little is known about DUI of Delta-8 THC, a newer cannabis product. Using 2022 survey data among 189 U.S. adults ages 18-25 (58.73% male, 59.26% non-Hispanic White), multivariable logistic regression examined substance-specific (alcohol, cannabis, Delta-8) DUI perceived likelihood and risk in relation to past-year DUI among those with past-year use of each. Overall, 72.49% reported past-year alcohol use, 50.53% cannabis, and 22.46% Delta-8. Among those reporting past-year use of each respective substance, 33.58% reported DUI of alcohol, 32.63% cannabis, and 57.14% Delta-8. On average, participants had the same DUI perceived likelihood ("somewhat unlikely") across substances and perceived alcohol DUI as riskiest. Higher alcohol DUI perceived likelihood and lower perceived risk were associated with alcohol-related DUI. Greater cannabis-related perceived likelihood (but not risk) was associated with cannabis-related DUI. Neither Delta-8 DUI perceived likelihood nor risk were associated with Delta-8 DUI. In sum, perceived DUI likelihood for alcohol, cannabis, or Delta-8 tended to be similar. Among those with past-year use of each, the proportion of DUI was highest for Delta-8. Interventions should target DUI-related perceived likelihood and promote protective behavioral strategies that reduce substance-specific DUI risk.

Cumulative Deleterious Effects of Tetrahydrocannabinoid (THC) and Ethanol on Mitochondrial Respiration and Reactive Oxygen Species Production Are Enhanced in Old Isolated Cardiac Mitochondria

Delta 9 tetrahydrocannabinol (THC), the main component of cannabis, has adverse effects on the cardiovascular system, but whether concomitant ethanol (EtOH) and aging modulate its toxicity is unknown. We investigated dose responses of THC and its vehicle, EtOH, on mitochondrial respiration and reactive oxygen production in both young and old rat cardiac mitochondria (12 and 90 weeks). THC dose-dependently impaired mitochondrial respiration in both groups, and such impairment was enhanced in aged rats (-97.5 ± 1.4% vs. -75.6 ± 4.0% at 2 × 10-5 M, and IC50: 0.7 ± 0.05 vs. 1.3 ± 0.1 × 10-5 M, p < 0.01, for old and young rats, respectively). The EtOH-induced decrease in mitochondrial respiration was greater in old rats (-50.1 ± 2.4% vs. -19.8 ± 4.4% at 0.9 × 10-5 M, p < 0.0001). Further, mitochondrial hydrogen peroxide (H2O2) production was enhanced in old rats after THC injection (+46.6 ± 5.3 vs. + 17.9 ± 7.8%, p < 0.01, at 2 × 10-5 M). In conclusion, the deleterious cardiac effects of THC were enhanced with concomitant EtOH, particularly in old cardiac mitochondria, showing greater mitochondrial respiration impairment and ROS production. These data improve our knowledge of the mechanisms potentially involved in cannabis toxicity, and likely support additional caution when THC is used by elderly people who consume alcohol.