Acute and residual mood and cognitive performance of young adults following smoked 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.

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.

Cannabis and Driving in Older Adults

Importance

Epidemiological studies have found that cannabis increases the risk of a motor vehicle collision. Cannabis use is increasing in older adults, but laboratory studies of the association between cannabis and driving in people aged older than 65 years are lacking.

Objective

To investigate the association between cannabis, simulated driving, and concurrent blood tetrahydrocannabinol (THC) levels in older adults.

Design, Setting, and Participants

Using an ecologically valid counterbalanced design, in this cohort study, regular cannabis users operated a driving simulator before, 30 minutes after, and 180 minutes after smoking their preferred legal cannabis or after resting. This study was conducted in Toronto, Canada, between March and November 2022 with no follow-up period. Data were analyzed from December 2022 to February 2023.

Exposures

Most participants chose THC-dominant cannabis with a mean (SD) content of 18.74% (6.12%) THC and 1.46% (3.37%) cannabidiol (CBD).

Main outcomes and measures

The primary end point was SD of lateral position (SDLP, or weaving). Secondary outcomes were mean speed (MS), maximum speed, SD of speed, and reaction time. Driving was assessed under both single-task and dual-task (distracted) conditions. Blood THC and metabolites of THC and CBD were also measured at the time of the drives.

Results

A total of 31 participants (21 male [68%]; 29 White [94%], 1 Latin American [3%], and 1 mixed race [3%]; mean [SD] age, 68.7 [3.5] years), completed all study procedures. SDLP was increased and MS was decreased at 30 but not 180 minutes after smoking cannabis compared with the control condition in both the single-task (SDLP effect size [ES], 0.30; b = 1.65; 95% CI, 0.37 to 2.93; MS ES, -0.58; b = -2.46; 95% CI, -3.56 to -1.36) and dual-task (SDLP ES, 0.27; b = 1.75; 95% CI, 0.21 to 3.28; MS ES, -0.47; b = -3.15; 95% CI, -5.05 to -1.24) conditions. Blood THC levels were significantly increased at 30 minutes but not 180 minutes. Blood THC was not correlated with SDLP or MS at 30 minutes, and SDLP was not correlated with MS. Subjective ratings remained elevated for 5 hours and participants reported that they were less willing to drive at 3 hours after smoking.

Conclusions and relevance

In this cohort study, the findings suggested that older drivers should exercise caution after smoking cannabis.

Agreement between momentary and retrospective reports of cannabis use and alcohol use: Comparison of ecological momentary assessment and timeline followback indices

OBJECTIVE

This study compares three methods of cannabis and of alcohol use assessment in a sample of regular cannabis users: (a) ecological momentary assessment (EMA) repeated momentary surveys aggregated to the daily level, (b) EMA morning reports (MR) where participants reported on their total use from the previous day, and (c) retrospective timeline followback (TLFB) interviews covering the same period of time as the EMA portion of the study. We assessed the overall correspondence between these methods in terms of cannabis and alcohol use occasions and also investigated predictors of agreement between methods.

METHOD

Forty-nine individuals aged 18-50 (Mage = 24.49, 49% female, 84% White) who reported regular cannabis use completed a 14-day EMA study. At the end of the EMA period, participants returned to the laboratory to complete a TLFB (administered via computer) corresponding to the same dates of the EMA period.

RESULTS

Daily aggregated EMA and TLFB reports showed a low to modest agreement for both alcohol and cannabis use. Overall, agreement between EMA and MR was better than agreement between EMA and TLFB, likely because less retrospection is required when only reporting on behavior from the previous day. Quantity and frequency of use differentially predicted agreement across reporting methods when assessing alcohol compared to cannabis. When reporting cannabis use, but not alcohol use, individuals who used more demonstrated higher agreement between EMA and TLFB.

CONCLUSIONS

Results suggest that retrospective reporting methods assessing alcohol and cannabis should not be considered a direct "substitute" for momentary or daily assessments. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Cannabis self-administration in the human laboratory: a scoping review of ad libitum studies

Cannabis self-administration studies may be helpful for identifying factors that influence cannabis consumption and subjective response to cannabis. Additionally, these paradigms could be useful for testing novel pharmacotherapies for cannabis use disorder. This scoping review aims to summarize the findings from existing ad libitum cannabis self-administration studies to determine what has been learned from these studies as well as their limitations. We examined studies that specifically examined cannabis smoking, focusing on subjective response and self-administration behavior (e.g., smoking topography). A systematic search was conducted using PubMed and Embase from inception to October 22, 2022. Our search strategy identified 26 studies (total N = 662, 79% male) that met our eligibility criteria. We found that tetrahydrocannabinol (THC) concentration significantly affected subjective response to cannabis in some but not all studies. In general, cannabis self-administration tended to be most intense at the beginning of the laboratory session and decreased in later parts of the session. There was limited data on cannabis self-administration in adults older than 55. Data on external validity and test-retest reliability were also limited. Addressing these limitations in future ad libitum cannabis self-administration studies could lead to more valid and generalizable paradigms, which in turn could be used to improve our understanding of cannabis use patterns and to help guide medication development for cannabis use disorder.

The Utility of THC Cutoff Levels in Blood and Saliva for Detection of Impaired Driving

Background: Δ9-Tetrahydrocannabinol (THC) is the psychoactive component in cannabis and a relationship of THC to driving impairment is expected. Despite this, there are discrepant findings with respect to the relationship of blood THC to driving. This study investigated the relationship of blood, urine, and saliva THC/THC-COOH levels to "weaving," as measured by a driving simulator. Methods: Participants smoked cannabis alone or with alcohol. THC/THC-COOH levels in blood, urine, and saliva were correlated with standard deviation of lateral position (SDLP), measuring "weaving." In addition, SDLP after cannabis and/or alcohol were compared with SDLP after placebo when THC/THC-COOH levels were above or below specified thresholds in blood (5 ng/mL), urine (50 ng/mL), or saliva (25 ng/mL). Results: A clear linear relationship between blood THC concentration and SDLP was not observed based on calculation of Spearman coefficients. When compared with placebo, SDLP was significantly increased after cannabis and cannabis combined with alcohol when THC in the blood was above the legal limit. SDLP was increased in drug conditions when saliva cutoffs were above the legal limit. Conclusions: The findings of this study suggest that specified thresholds for THC in blood and saliva may be able to detect driving impairment, but future studies are needed. ClinicalTrials.gov ID: NCT03106363.

The "Next Day" Effects of Cannabis Use: A Systematic Review

Background: Δ⁹-Tetrahydrocannabinol (THC), the main intoxicating component of cannabis, can cause cognitive and psychomotor impairment. Whether this impairment is still present many hours or even days after THC use requires clarification. Possible "next day" effects are of major significance in safety-sensitive workplaces. We therefore conducted a systematic review of studies investigating the "next day" effects of THC. Methods: Studies that measured performance on safety-sensitive tasks (e.g., driving, flying) and/or neuropsychological tests >8 h after THC (or cannabis) use using interventional designs were identified by searching two online databases from inception until March 28, 2022. Risk of bias (RoB) was evaluated using the relevant Cochrane tools. Results were described in terms of whether THC had a significant effect on performance relative to the primary comparator (i.e., placebo or baseline, as appropriate). Results: Twenty studies (n=458) involving 345 performance tests were reviewed. Most studies administered a single dose of THC (median [interquartile range]: 16 [11-26] mg) and assessed performance between >12 and 24 h post-treatment. N=209/345 tests conducted across 16 published studies showed no "next day" effects of THC. Nine of these 16 studies used randomized, double-blind, placebo-controlled designs. Half (N=8) had "some" RoB, and half (N=8) had a "high" RoB. Notably, N=88 of these 209 tests failed to demonstrate "acute" (i.e., <8 h post-treatment) THC-induced impairment. N=12/345 tests conducted across five published studies indicated negative (i.e., impairing) "next day" effects of THC. None of these five studies used randomized, double-blind, placebo-controlled designs and all were published >18 years ago (four, >30 years ago). Three had "some" RoB, and two had a "high" RoB. A further N=121/345 tests indicated "unclear" "next day" effects of THC with insufficient information provided to assess outcomes. The remaining N=3/345 tests indicated positive (i.e., enhancing) "next day" effects of THC. Conclusions: Some lower quality studies have reported "next day" effects of THC on cognitive function and safety-sensitive tasks. However, most studies, including some of higher quality, have found no such effect. Overall, it appears that there is limited scientific evidence to support the assertion that cannabis use impairs "next day" performance. Further studies involving improved methodologies are required to better address this issue.

Association between ABCB1 rs2235048 Polymorphism and THC Pharmacokinetics and Subjective Effects following Smoked Cannabis in Young Adults

Genetic influences on acute responses to psychoactive drugs may contribute to individual variability in addiction risk. ABCB1 is a human gene that encodes P-glycoprotein, an ATP-dependent efflux pump that may influence the pharmacokinetics of delta-9-tetrahydrocannabinol (THC), the primary psychoactive component of cannabis. Using data from 48 young adults (aged 19-25 years) reporting 1-4 days of cannabis use per week who completed a placebo-controlled human laboratory experiment, we tested the hypothesis that the rs2235048 polymorphism of ABCB1 would influence acute responses to smoked cannabis. C-allele carriers reported on average greater frequency of weekly cannabis use compared to the TT genotype carriers (TC/CC mean ± SEM = 2.74 ± 0.14, TT = 1.85 ± 0.24, p = 0.004). After smoking a single cannabis cigarette to their desired high, C-allele carriers had higher area-under-the-curve (AUC) of both THC metabolites (11-OH-THC TC/CC = 7.18 ± 9.64, TT = 3.28 ± 3.40, p = 0.05; THC-COOH TC/CC = 95.21 ± 116.12, TT = 45.92 ± 42.38, p = 0.043), and these results were impact by self-reported ethnicity. There were no significant differences in self-reported subjective drug effects except for a greater AUC of visual analogue scale rating of drug liking (TC/CC = 35,398.33 ± 37,233.72, TT = 15,895.56 ± 13,200.68, p = 0.017). Our preliminary findings suggest that further work in a larger sample should investigate whether human ABCB1 influences cannabis-related phenotypes and plays a role in the risk of developing a cannabis use disorder.

Separate and combined effects of alcohol and cannabis on mood, subjective experience, cognition and psychomotor performance: A randomized trial

Co-use of alcohol and cannabis is associated with increased frequency and intensity of use and related problems. This study examined acute effects of alcohol and cannabis on mood, subjective experience, cognition, and psychomotor performance. Twenty-eight healthy cannabis users aged 19-29 years with recent history of binge drinking completed this within-subjects, double-blind, double-dummy, placebo-controlled, randomized clinical trial. Participants received: placebo alcohol and placebo cannabis (<0.1% THC); alcohol (target breath alcohol content [BrAC] 80 mg/dL) and placebo cannabis; placebo alcohol and active cannabis (12.5% THC); and active alcohol and cannabis over four sessions. Profile of Mood States (POMS), Addiction Research Centre Inventory (ARCI), verbal free recall (VFR), Digit Symbol Substitution Test (DSST), Continuous Performance Test (CPT), and grooved pegboard (GPB) task were administered before and approximately 75 min after drinking alcohol (1 h after smoking cannabis ad libitum). Significant effects of condition were found for the POMS (Tension-Anxiety, Confusion) and ARCI (MBG, LSD, PCAG, Euphoria, Sedation), predominantly with greater increases emerging after cannabis or alcohol-cannabis combined relative to placebo. Significant effects were found for VFR (immediate total and delayed recall, percent retained), DSST (trials attempted, trials correct, reaction time), and GPB (non-dominant hand) predominantly with greater declines in performance after alcohol and alcohol-cannabis combined relative to placebo and/or cannabis. Cannabis appeared to affect mood and subjective experience, with minimal impact on cognitive performance. Alcohol appeared to impair cognitive and psychomotor performance, with minimal impact on mood and subjective experience. Acute effects of alcohol and cannabis combined were additive at most.

The Determination of Cannabinoids in Urine Samples Using Microextraction by Packed Sorbent and Gas Chromatography-Mass Spectrometry

Cannabis is the most consumed illicit drug worldwide, and its legal status is a source of concern. This study proposes a rapid procedure for the simultaneous quantification of Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH), cannabidiol (CBD), and cannabinol (CBN) in urine samples. Microextraction by packed sorbent (MEPS) was used to pre-concentrate the analytes, which were detected by gas chromatography–mass spectrometry. The procedure was previously optimized, and the final conditions were: conditioning with 50 µL methanol and 50 µL of water, sample load with two draw–eject cycles, and washing with 310 µL of 0.1% formic acid in water with 5% isopropanol; the elution was made with 35 µL of 0.1% ammonium hydroxide in methanol. This fast extraction procedure allowed quantification in the ranges of 1–400 ng/mL for THC and CBD, 5–400 ng/mL for CBN and 11-OH-THC, and 10–400 ng/mL for THC-COOH with coefficients of determination higher than 0.99. The limits of quantification and detection were between 1 and 10 ng/mL using 0.25 mL of sample. The extraction efficiencies varied between 26 and 85%. This analytical method is the first allowing the for determination of cannabinoids in urine samples using MEPS, a fast, simple, and low-cost alternative to conventional techniques.

Cannabis use as a predictor and outcome of positive and negative affect in college students: An ecological momentary assessment study

BACKGROUND

Reinforcement models identify negative affect (NA) and positive affect (PA) to be important momentary determinants and outcomes of cannabis use. Sensitization and allostatic models further suggest that these mood-cannabis associations are stronger among individuals with more cannabis-related problems. Despite this theoretical background and the fact that cannabis is commonly used for its mood-enhancing effects among college students, surprisingly, little is known about the momentary associations between mood and cannabis use in this population.

AIMS

To examine the associations between (a) momentary within-person variations in NA (worried, stressed, nervous) and PA (happy, enthusiastic, proud, excited) and intention to use cannabis within the next hour, (b) the within-person variations in time elapsed since last cannabis use, amount used and momentary NA and PA, and (c) to test whether cannabis-related problems moderate the stated associations.

METHOD

Eighty, more-than-weekly, cannabis using students at the University of Amsterdam reported on cannabis use, NA and PA three times daily for 14 consecutive days. Mixed-effects models were performed to analyze the dataset.

RESULTS

Within-persons, relatively high PA and low NA were associated with a higher likelihood of intending to use cannabis. Within-persons, more recent and greater amounts of cannabis use were associated with relatively high PA. More recent cannabis use was associated with relatively low NA. Cannabis-related problems did not moderate the associations.

CONCLUSIONS

While recent cannabis use related to higher PA and lower NA, high PA but low NA preceded use, supporting positive reinforcement rather than negative reinforcement in this college sample of regular cannabis users.

A Comparison of Acute Neurocognitive and Psychotomimetic Effects of a Synthetic Cannabinoid and Natural Cannabis at Psychotropic Dose Equivalence

Due to differences in potency, efficacy, and affinity for CB1 receptors, similarities and differences in psychoactive effect profiles of natural cannabis and synthetic cannabinoids (SCs) cannot reliably be derived from equipotent dose comparisons. Instead, the current study proposes to compare the intrinsic psychoactive effects of natural cannabis (THC) and an SC, JWH-018, at psychotropic dose equivalence. Participants from two placebo-controlled studies were matched for their levels of subjective high to compare neurocognitive and psychotomimetic effects of THC and JWH-018. At equal subjective intoxication levels, both drugs impaired psychomotor, divided attention, and impulse control, with no significant difference between the two drugs. Both drugs also caused significant psychotomimetic effects, but dissociative effects were considerably more pronounced for JWH-018 than THC. We conclude that psychotropic dose equivalence provides a uniform approach for comparing the neurocognitive and psychotomimetic profiles of CB1 agonists, which can also be applied to other drug classes.

Influence of Cannabinoid Receptor 1 Genetic Variants on the Subjective Effects of Smoked Cannabis

As many jurisdictions consider relaxing cannabis legislation and usage is increasing in North America and other parts of the world, there is a need to explore the possible genetic differences underlying the subjective effects of cannabis. This pilot study investigated specific genetic variations within the cannabinoid receptor 1 (CNR1) gene for association with the subjective effects of smoked cannabis. Data were obtained from a double-blinded, placebo-controlled clinical trial studying the impact of cannabis intoxication on driving performance. Participants randomized to the active cannabis group who consented to secondary genetic analysis (n = 52) were genotyped at the CNR1 rs1049353 and rs2023239 polymorphic areas. Maximum value and area under the curve (AUC) analyses were performed on subjective measures data. Analysis of subjective effects by genotype uncovered a global trend towards greater subjective effects for rs1049353 T-allele- and rs2023239 C-allele-carrying subjects. However, significant differences attributed to allelic identity were only documented for a subset of subjective effects. Our findings suggest that rs1049353 and rs2023239 minor allele carriers experience augmented subjective effects during acute cannabis intoxication.

Are the Acute Effects of THC Different in Aging Adults?

In recent years of expanding legalization, older adults have reported the largest increase in cannabis use of any age group. While its use has been studied extensively in young adults, little is known about the effects of THC in older adults and whether the risks of cannabis might be different, particularly concerning intoxication and cognition. The current study investigated whether age is associated with the deleterious effects of THC on cognitive performance and other behavioral measures before and after ad libitum self-administration of three different types of cannabis flower (THC dominant, THC + CBD, and CBD dominant). Age groups consisted of young adults (ages 21–25) and older adults (ages 55–70). Controlling for pre-use scores on all measures, the THC dominant chemovar produced a greater deleterious effect in younger adults compared with older adults in tests of learning and processing speed, whereas there were no differences between old and young in the effects of the other chemovars. In addition, the young group reported greater cannabis craving than the older group after using the THC chemovar. Consistent with some reports in the preclinical literature, the findings suggest that older adults may be less sensitive to the effects of THC on cognitive and affective measures.

Cannabis use and cannabis use disorder

Cannabis use disorder (CUD) is an underappreciated risk of using cannabis that affects ~10% of the 193 million cannabis users worldwide. The individual and public health burdens are less than those of other forms of drug use, but CUD accounts for a substantial proportion of persons seeking treatment for drug use disorders owing to the high global prevalence of cannabis use. Cognitive behavioural therapy, motivational enhancement therapy and contingency management can substantially reduce cannabis use and cannabis-related problems, but enduring abstinence is not a common outcome. No pharmacotherapies have been approved for cannabis use or CUD, although a number of drug classes (such as cannabinoid agonists) have shown promise and require more rigorous evaluation. Treatment of cannabis use and CUD is often complicated by comorbid mental health and other substance use disorders. The legalization of non-medical cannabis use in some high-income countries may increase the prevalence of CUD by making more potent cannabis products more readily available at a lower price. States that legalize medical and non-medical cannabis use should inform users about the risks of CUD and provide information on how to obtain assistance if they develop cannabis-related mental and/or physical health problems.

Human Laboratory Models of Cannabis Use: Applications for Clinical and Translational Psychiatry Research

Cannabis is increasingly used by individuals with mental health diagnoses and often purported to treat anxiety and various other psychiatric symptoms. Yet support for using cannabis as a psychiatric treatment is currently limited by a lack of evidence from rigorous placebo-controlled studies. While regulatory hurdles and other barriers make clinical trials of cannabis challenging to conduct, addiction researchers have decades of experience studying cannabis use in human laboratory models. These include methods to control cannabis administration, to delineate clinical and mechanistic aspects of cannabis use, and to evaluate potential treatment applications for cannabis and its constituents. In this paper, we review these human laboratory procedures and describe how each can be applied to study cannabis use in patients with psychiatric disorders. Because anxiety disorders are among the most common psychiatric illnesses affecting American adults, and anxiety relief is also the most commonly-reported reason for medicinal cannabis use, we focus particularly on applying human laboratory models to study cannabis effects in individuals with anxiety and related disorders. Finally, we discuss how these methods can be integrated to study cannabis effects in other psychiatric conditions and guide future research in this area.

Dissecting the role of CB1 and CB2 receptors in cannabinoid reward versus aversion using transgenic CB1- and CB2-knockout mice

Cannabinoids produce both rewarding and aversive effects in humans and experimental animals. However, the mechanisms underlying these conflicting findings are unclear. Here we examined the potential involvement of CB1 and CB2 receptors in cannabinoid action using transgenic CB1-knockout (CB1-KO) and CB2-knockout (CB2-KO) mice. We found that Δ9-tetrahydrocannabinol (Δ9-THC) induced conditioned place preference at a low dose (1 mg/kg) in WT mice that was attenuated by deletion of the CB1 receptor. At 5 mg/kg, no subjective effects of Δ9-THC were detected in WT mice, but CB1-KO mice exhibited a trend towards place aversion and CB2-KO mice developed significant place preferences. This data suggests that activation of the CB1 receptor is rewarding, while CB2R activation is aversive. We then examined the nucleus accumbens (NAc) dopamine (DA) response to Δ9-THC using in vivo microdialysis. Unexpectedly, Δ9-THC produced a dose-dependent decrease in extracellular DA in WT mice, that was potentiated in CB1-KO mice. However, in CB2-KO mice Δ9-THC produced a dose-dependent increase in extracellular DA, suggesting that activation of the CB2R inhibits DA release in the NAc. In contrast, Δ9-THC, when administered systemically or locally into the NAc, failed to alter extracellular DA in rats. Lastly, we examined the locomotor response to Δ9-THC. Both CB1 and CB2 receptor mechanisms were shown to underlie Δ9-THC-induced hypolocomotion. These findings indicate that Δ9-THC's variable subjective effects reflect differential activation of cannabinoid receptors. Specifically, the opposing actions of CB1 and CB2 receptors regulate cannabis reward and aversion, with CB2-mediated effects predominant in mice.

Effects of chronic exposure to low doses of Δ9- tetrahydrocannabinol in adolescence and adulthood on serotonin/norepinephrine neurotransmission and emotional behaviors

BACKGROUND

Chronic exposure to the Δ9-tetrahydrocannabinol (THC), the main cannabis pharmacological component, during adolescence has been shown to be associated with an increased risk of depression and suicidality in humans.

AIMS

Little is known about the impact of the long-term effects of chronic exposure to low doses of THC in adolescent compared to adult rodents.

METHODS

THC (1mg/kg i.p., once a day) or vehicle was administered for 20 days in both adolescent (post-natal day, PND 30-50) and young adult rats (PND 50-70). After a long washout period (20 days), several behavioral paradigms and electrophysiological recordings of serotonin (5-HT) and norepinephrine (NE) neurons were carried out.

RESULTS

Adolescent THC exposure resulted in depressive lbehaviors: a significant decrease in latency to first immobility in the forced swim test, increased anhedonia in the sucrose preference test. Decrease entries in the open arm were observed in the elevated plus maze after adolescent and adult exposure, indicating anxiousphenotype. A significant reduction in dorsal raphe serotonergic neural activity without changing locus coeruleus noradrenergic neural activity was found in THC adolescent and adult exposure.

CONCLUSIONS

Altogether, these findings suggest that low doses of chronic THC exposure during the developmental period and adulthood could result in increased vulnerability of the 5-HT system and anxiety symptoms; however, depressive phenotypes occur only after adolescent, but not adult exposure, underscoring the higher vulnerability of young ages to the mental effects of cannabis.