THCCOOH concentrations in whole blood: are they useful in discriminating occasional from heavy smokers?

Cannabis Use and Biomarkers of Inflammation, Immune Activation, and Microbial Translocation in Persons with HIV

Background: The relationship between cannabis and inflammation among persons with HIV (PWH) remains unclear. We examined whether the cannabis metabolite 11-nor-9-carboxy THC (THC-COOH) is associated with lower levels of plasma biomarkers of inflammation, immune activation, and microbial translocation in PWH. We hypothesized that cannabis use would be associated with lower levels of plasma inflammatory biomarkers than noncannabis use. Methods: We quantified THC-COOH in plasma, with THC-COOH levels between 5.1-69.9 μg/L and ≥70 μg/L being classified as moderate and heavy cannabis use, respectively, with noncannabis use defined as undetected THC-COOH. We measured a panel of plasma biomarkers of inflammation (interleukin [IL]-1-β, tumor necrosis factor-alpha, IL-18, IL-6, and C-reactive protein), immune activation (CD14 and CD163), and microbial translocation (iFABP2 and lipopolysaccharide binding protein [LBP]), with all biomarkers collected on the same day. We used a cross-sectional design and linear regression models to test whether cannabis use is associated with lower biomarker levels. Results: Participants were (N=107) sexual minority men with HIV (median age=32 years, IQR=28, 38), of whom 65% were virally suppressed; 36%, 44%, and 20% were classified as nonuse, moderate, and heavy cannabis, respectively. In linear regression models adjusted for viral suppression, stimulant use, and CD4 counts, heavy cannabis use was significantly associated with lower levels of log10 LBP (β=-0.14, 95% confidence interval: -0.24 to -0.04; false discovery rate=0.0029; partial eta squared=0.07) than noncannabis users. No precise associations were observed for other biomarkers (all p>0.05). Conclusions: Our findings suggest that cannabis use may be associated with lower plasma LBP. Further work is needed to clarify the relationship between cannabis use and biomarkers of microbial translocation in PWH.

HIV Prevention and Care Among Black Cisgender Sexual Minority Men and Transgender Women: Protocol for an HIV Status-Neutral Cohort Study Using an Observational-Implementation Hybrid Approach

BACKGROUND

Black cisgender gay, bisexual, and other sexual minority men (SMM) and transgender women (TW) continue to be heavily affected by HIV. Further research is needed to better understand HIV prevention and care outcomes in this population. In particular, there is a need for research examining the impact of substance use and sleep health on HIV prevention and treatment outcomes among Black SMM and TW.

OBJECTIVE

This paper outlines the study methods being used in the recently launched follow-up study to the Neighborhoods and Networks (N2) study, which we refer to as N2 Part 2 (N2P2). N2P2 aims to address this gap in the literature, build off the findings of the original N2 study, and identify socioenvironmental determinants of health, including whether neighborhood and network factors mediate and moderate these relationships.

METHODS

Building on the N2 cohort study in Chicago from 2018 to 2022, N2P2 used a prospective longitudinal cohort design and an observational-implementation hybrid approach. With sustained high levels of community engagement, we aim to recruit a new sample of 600 Black SMM and TW participants residing in the Chicago metropolitan statistical area. Participants are asked to participate in 3 study visits across an 18-month study period (1 visit every 9 months). Four different forms of data are collected per wave: (1) an in-person survey, (2) biological specimen collection, (3) a daily remote ecological momentary assessment for 14 days after each study visit, and (4) data from electronic health records. These forms of data collection continue to assess neighborhood and network factors and specifically explore substance use, sleep, immune function, obesity, and the implementation of potential interventions that address relevant constructs (eg, alcohol use and pre-exposure prophylaxis adherence).

RESULTS

The N2P2 study was funded in August 2021 by the National Institute of Drug Abuse (R01DA054553 and R21DA053156) and National Heart, Lung, and Blood Institute (R01HL160325). This study was launched in November 2022. Recruitment and enrollment for the first wave of data collection are currently ongoing.

CONCLUSIONS

The N2P2 study is applying innovative methods to comprehensively explore the impacts of substance use and sleep health on HIV-related outcomes among an HIV status-neutral cohort of Black SMM and TW in Chicago. This study is applying an observational-implementation hybrid design to help us achieve findings that support rapid translation, a critical priority among populations such as Black SMM and TW that experience long-standing inequities with regard to HIV and other health-related outcomes. N2P2 will directly build off the findings that have resulted from the original N2 study among Black SMM and TW in Chicago. These findings provide a better understanding of multilevel (eg, individual, network, and neighborhood) factors that contribute to HIV-related outcomes and viral suppression among Black SMM and TW.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/48548.

Cytosolic Enzymes Generate Cannabinoid Metabolites 7-Carboxycannabidiol and 11-Nor-9-carboxytetrahydrocannabinol

The cannabinoids cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) undergo extensive oxidative metabolism in the liver. Although cytochromes P450 form the primary, pharmacologically active, hydroxylated metabolites of CBD and THC, less is known about the enzymes that generate the major in vivo circulating metabolites of CBD and THC, 7-carboxy-CBD and 11-carboxy-THC, respectively. The purpose of this study was to elucidate the enzymes involved in forming these metabolites. Cofactor dependence experiments with human liver subcellular fractions revealed that 7-carboxy-CBD and 11-carboxy-THC formation is largely dependent on cytosolic NAD+-dependent enzymes, with lesser contributions from NADPH-dependent microsomal enzymes. Experiments with chemical inhibitors provided evidence that 7-carboxy-CBD formation is mainly dependent on aldehyde dehydrogenases and 11-carboxy-THC formation is mediated also in part by aldehyde oxidase. This study is the first to demonstrate the involvement of cytosolic drug-metabolizing enzymes in generating major in vivo metabolites of CBD and THC and addresses a knowledge gap in cannabinoid metabolism.

Antiviral activities of hemp cannabinoids

Hemp is an understudied source of pharmacologically active compounds and many unique plant secondary metabolites including more than 100 cannabinoids. After years of legal restriction, research on hemp has recently demonstrated antiviral activities in silico, in vitro, and in vivo for cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiolic acid (CBDA), cannabigerolic acid (CBGA), and several other cannabinoids against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), human immunodeficiency virus (HIV), and γ-herpes viruses. Mechanisms of action include inhibition of viral cell entry, inhibition of viral proteases, and stimulation of cellular innate immune responses. The anti-inflammatory properties of cannabinoids are also under investigation for mitigating the cytokine storm of COVID-19 and controlling chronic inflammation in people living with HIV. Retrospective clinical studies support antiviral activities of CBD, Δ9-THC, and cannabinoid mixtures as do some prospective clinical trials, but appropriately designed clinical trials of safety and efficacy of antiviral cannabinoids are urgently needed.

Objective Identification of Cannabis Use Levels in Clinical Populations Is Critical for Detecting Pharmacological Outcomes

Introduction: Cannabis is widely used for recreational and medical purposes, but its therapeutic efficacy remains unresolved for many applications as data from retrospective studies show dramatic discrepancy. We hypothesized that false self-reporting of cannabis use and lack of differentiation of heavy users from light or occasional users contribute to the conflicting outcomes. Objective: The goal of this study was to develop an objective biomarker of cannabis use and test how application of such biomarker impacts clinical study outcomes and dose-response measures. Methods and Analysis: Population pharmacokinetic (PK) models of (-)-trans-Δ9-tetrahydrocannabinol (THC) and its metabolites 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (11-COOH-THC) were developed based on published studies reporting cannabinoid disposition in individual subjects following intravenous administration or smoking of cannabis. Plasma 11-COOH-THC concentration distributions in different cannabis user groups smoking cannabis were generated via Monte Carlo simulations, and plasma concentration cutoff values of 11-COOH-THC were developed to differentiate light and heavy daily cannabis users in clinical studies. The developed cutoff value was then applied to a retrospective study that assessed the impact of cannabis use on T cell activation in subjects with HIV who self-reported as either nonuser or daily user of cannabis. Results: The developed population PK models established plasma 11-COOH-THC concentration of 73.1 μg/L as a cutoff value to identify heavy daily users, with a positive predictive value of 80% in a mixed population of equal proportions of once daily and three times a day users. The stratification allowed detection of changes in T cell activation in heavy users which was not detected based on self-reporting or detectability of plasma cannabinoids. A proof-of-concept power analysis demonstrated that implementation of such cutoff value greatly increases study power and sensitivity to detect pharmacological effects of cannabis use. Conclusions: This study shows that the use of plasma 11-COOH-THC concentration cutoff value as an objective measure to classify cannabis use in target populations is critical for study sensitivity and specificity and provides much needed clarity for addressing dose-response relationships and therapeutic effects of cannabis.

Quantitative determination of five cannabinoids in blood and urine by gas chromatography tandem mass spectrometry applying automated on-line solid phase extraction

Cannabis is the most frequently consumed illegal substance worldwide. More recently, an increasing number of legal cannabis products low in psychoactive Δ⁹‐tetrahydrocannabinol (THC) but high in non‐intoxicating cannabidiol (CBD) are being more widely consumed. While the detection and quantification of THC and its metabolites in biological matrices is an important forensic‐toxicological task, additional detection of CBD is also important, for example, when examining the plausibility of consumer's statements. This report describes the method validation for the quantitative determination of THC and its two major metabolites, 11‐hydroxy‐THC (OH‐THC) and 11‐nor‐9‐carboxy‐THC (THC‐COOH), as well as CBD and cannabinol (CBN) in whole blood and urine. The method employs automated on‐line solid phase extraction coupled to gas chromatography tandem mass spectrometry (GC–MS/MS). The method was fully validated according to guidelines of the Swiss Society of Legal Medicine (SGRM) and the Society of Toxicological and Forensic Chemistry (GTFCh). The method fulfilled the validation criteria regarding analytical limits, accuracy and precision, extraction efficacy, and sample stability. The limits of detection (LODs) in whole blood and urine were 0.15 ng/mL for THC, OH‐THC and CBD, 0.1 ng/mL for CBN, and 1.0 ng/mL for THC‐COOH. The limits of quantification (LOQ) in whole blood and urine were 0.3 ng/mL for THC, OH‐THC and CBD, 0.2 ng/mL for CBN, and 3.0 ng/mL for THC‐COOH. The fully validated and automated method allows sensitive and robust measurement of cannabinoids in whole blood and urine. Detection of CBD provides additional information regarding consumed products.

Metabolites of Cannabis Induce Cardiac Toxicity and Morphological Alterations in Cardiac Myocytes

Cannabis is one of the most commonly used recreational drugs worldwide. Rrecent epidemiology studies have linked increased cardiac complications to cannabis use. However, this literature is predominantly based on case incidents and post-mortem investigations. This study elucidates the molecular mechanism of Δ9-tetrahydrocannabinol (THC), and its primary metabolites 11-Hydroxy-Δ9-THC (THC-OH) and 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THC-COOH). Treatment of cardiac myocytes with THC-OH and THC-COOH increased cell migration and proliferation (p < 0.05), with no effect on cell adhesion, with higher doses (250–100 ng/mL) resulting in increased cell death and significant deterioration in cellular architecture. Conversely, no changes in cell morphology or viability were observed in response to THC. Expression of key ECM proteins α-SMA and collagen were up-regulated in response to THC-OH and THC-COOH treatments with concomitant modulation of PI3K and MAPK signalling. Investigations in the planarian animal model Polycelis nigra demonstrated that treatments with cannabinoid metabolites resulted in increased protein deposition at transection sites while higher doses resulted in significant lethality and decline in regeneration. These results highlight that the key metabolites of cannabis elicit toxic effects independent of the parent and psychoactive compound, with implications for cardiotoxicity relating to hypertrophy and fibrogenesis.

Analytical findings in a non-fatal intoxication with the synthetic cannabinoid 5F-ADB (5F-MDMB-PINACA): a case report

The case report centres on analytical findings from a spice sample (mixed with tobacco (as a cigarette) for consumption), and its corresponding plasma sample, smoked by a 31-year-old man who was attended by emergency services following collapse. The man was fully conscious and cooperative during initial medical treatment. Suddenly, he suffered a complete loss of self-control, whereupon the police was notified. The man encountered the police officers when exiting the apartment, at which point he threatened them with clenched fists and reached for a plant bucket in order to strike out in the direction of the officers. At the trial, he described himself as confused and as being completely overwhelmed, having lost self-control, suffered a panic attack and “just wanted to get out the situation”. Furthermore, he stated that he had no recollection of the incident. He feared death due to palpitations, heart pain, dizziness and repetitive anxiety states. Routine systematic as well as extended toxicological analysis of the plasma sample, taken approximately 2 h after the incident, confirmed the use of cannabis and spice. Plasma concentrations of THC, OH-THC and THC-COOH were 8.0 μg/L, 4.0 μg/L and 147 μg/L, respectively. Furthermore, analysis confirmed uptake of 5F-ADB (5F-MDMB-PINACA) via detection of both 5F-ADB and the 5F-ADB N-(5-OH-pentyl) metabolite. The spice sample additionally contained 5F-MDMB-PICA, which was not detected in the plasma sample. A differentiation between a possible co-use and a recent use of cannabis was not possible. In summary, this case once more underlines the health risks of spice use.

Analysis of 14 endocannabinoids and endocannabinoid congeners in human plasma using column switching high-performance atmospheric pressure chemical ionization liquid chromatography-mass spectrometry

The endocannabinoid system (ECS) is a complex cell-signaling system. To address the growing need of analytics capturing endocannabinoid levels to investigate the ECS, we developed and validated an assay for the quantitative analysis of 14 endocannabinoids and congeners. A simple extraction using protein precipitation with acetonitrile followed by online-trapping high-performance liquid chromatography-tandem mass spectrometry (LC/LC-MS/MS) was used to monitor the levels of 14 endocannabinoids in plasma. The assay was validated and intra-run and inter-run accuracies and imprecisions as well as matrix effects, recoveries, and sample stabilities were determined. As a proof of concept, a subset of study samples after naturalistic administration of Cannabis flower and concentrate was analyzed. With the exception of N-oleoyl dopamine and oleamide, all endocannabinoids fulfilled the predefined acceptance criteria. Reproducible recoveries and no significant matrix effects were observed. Sample stability was an issue. Analysis of the proof-of-concept study samples revealed a significantly (p = 0.006) higher concentration of docosatetraenoyl ethanolamide in concentrate users (300 ± 13 pg/mL) compared to flower users (252 ± 11 pg/mL). A robust, sensitive high-throughput assay for the quantitation of 14 endocannabinoids and congeners was successfully validated. Our study showed that it is mandatory to (A) appropriately stabilize samples and (B) separate and separately quantify 1-AG and 2-AG; otherwise, study results are unreliable. The analysis of study samples from Cannabis flower users versus Cannabis concentrate users revealed higher levels of docosatetraenoyl ethanolamide and anandamide (n.s.) in high THC concentrate users in accordance with the existing literature, supporting the validity of the assay measurements. Graphical abstract.

Alcohol and illicit drugs in drivers involved in road traffic crashes in Italy. An 8-year retrospective study

This study aims to investigate the prevalence of alcohol and drugs of abuse in Italian drivers involved in road traffic crashes between 2011 and 2018. Toxicological analyses were performed on the whole blood of 7593 injured drivers. Alcohol and illicit drugs, namely tetrahydrocannabinol (THC; cut-off 2ng/ml), cocaine (cut-off 10ng/ml), illicit opiates (cut-off 10ng/ml) and amphetamines (amphetamine, methamphetamine, MDMA, MDA; cut-off 20ng/ml) were investigated. The age and gender of the driver, the time of the crash (weekend/weekday and day/night), the road crash year and Blood Alcohol Concentration (BAC) were also considered. The 16.2% of samples tested positive for alcohol, 2.5% for cocaine, followed by opiates (2.0%), cannabinoids (1.5%), and amphetamines (0.5%). The overall prevalence of alcohol and drugs was lower than those reported in previous epidemiological studies of the DRUID project. The year 2011 showed the highest prevalence of drug-positive cases (24.1%), while the lowest prevalence was found in 2016 (16.8%), after the update of the Road Traffic Law (RTL) that increased punishments for driving under the influence. A progressive increase in the number of alcohol-positive female drivers was observed from 2011 to 2018, and the highest prevalence was found in the 26-35-year-old age range. Illicit drugs showed the highest overall prevalence in drivers <26 years of age but, if considering single drugs, cocaine and opiates were mostly found in subjects older than 36 years of age. A higher percentage of drug-positive drivers was found on weekend nights for alcohol and on both weekend and weekday nights for drugs. The types of drugs used by drivers did not change during the studied period.

Heavy Cannabis Use Associated With Reduction in Activated and Inflammatory Immune Cell Frequencies in Antiretroviral Therapy-Treated Human Immunodeficiency Virus-Infected Individuals

Background

Cannabis is a widely used drug in the United States, and the frequency of cannabis use in the human immunodeficiency virus (HIV)-infected population is disproportionately high. Previous human and macaque studies suggest that cannabis may have an impact on plasma viral load; however, the relationship between cannabis use and HIV-associated systemic inflammation and immune activation has not been well defined.

Methods

The impact of cannabis use on peripheral immune cell frequency, activation, and function was assessed in 198 HIV-infected, antiretroviral-treated individuals by flow cytometry. Individuals were categorized into heavy, medium, or occasional cannabis users or noncannabis users based on the amount of the cannabis metabolite 11-nor-carboxy-tetrahydrocannabinol (THC-COOH) detected in plasma by mass spectrometry.

Results

Heavy cannabis users had decreased frequencies of human leukocyte antigen (HLA)-DR+CD38+CD4+ and CD8+ T-cell frequencies, compared to frequencies of these cells in non-cannabis-using individuals. Heavy cannabis users had decreased frequencies of intermediate and nonclassical monocyte subsets, as well as decreased frequencies of interleukin 23- and tumor necrosis factor-α-producing antigen-presenting cells.

Conclusions

While the clinical implications are unclear, our findings suggest that cannabis use is associated with a potentially beneficial reduction in systemic inflammation and immune activation in the context of antiretroviral-treated HIV infection.

Driving Under the Influence of Cannabis: A Framework for Future Policy

Marijuana is the most widely consumed illicit substance in the United States, and an increasing number of states have legalized it for both medicinal and recreational purposes. As it becomes more readily available, there will be a concurrent rise in the number of users and, consequently, the number of motor vehicle operators driving under the influence. This article examines the cognitive and psychomotor effects of cannabis, as well as current policy concerning driving under the influence of drugs. The authors performed a MEDLINE search on the epidemiology of cannabis use, its cognitive and psychomotor effects, and policies regarding driving under the influence of drugs. Twenty-eight epidemiological studies, 16 acute cognitive and psychomotor studies, 8 chronic cognitive and psychomotor studies, and pertinent state and federal laws and policies were reviewed. These search results revealed that marijuana use is associated with significant cognitive and psychomotor effects. In addition, the legalization of marijuana varies from state to state, as do the laws pertaining to driving under the influence of drugs. Marijuana is a commonly found illicit substance in motor vehicle operators driving under the influence of drugs. Current evidence shows that blood levels of tetrahydrocannabinol do not correlate well with the level of impairment. In addition, although acute infrequent use of cannabis typically leads to cognitive and psychomotor impairment, this is not consistently the case for chronic heavy use. To establish the framework for driving under the influence of cannabis policy, we must review the current published evidence and examine existing policy at state and federal levels.

Post-mortem distribution of the synthetic cannabinoid MDMB-CHMICA and its metabolites in a case of combined drug intoxication

This case report centres on the post-mortem distribution of the synthetic cannabinoid MDMB-CHMICA and its metabolites in the case of a 27-year-old man found dead after falling from the 24th floor of a high-rise building. Toxicological analysis of post-mortem samples confirmed, besides consumption of the synthetic cannabinoids MDMB-CHMICA (1.7 ng/mL femoral blood) and EG-018, the abuse of THC (9.3 ng/mL femoral blood), amphetamine (1050 ng/mL femoral blood), MDMA (275 ng/mL femoral blood), and cocaine. Regarding EG-018 and cocaine, only traces were detected in heart blood as well as in the brain (EG-018) and urine (cocaine), respectively, which is why no quantification was conducted in the femoral blood sample. It was concluded from femoral blood analysis that, at the time of death, the man was under the influence of the synthetic cannabinoid MDMB-CHMICA, THC, amphetamine and MDMA. Comprehensive screenings of all post-mortem specimens were conducted to elucidate the post-mortem distribution of MDMB-CHMICA and its metabolites. The MDMB-CHMICA concentrations ranged between 0.01 ng/mL (urine) and 5.5 ng/g (brain). Comparably low concentrations were detected in cardiac and femoral blood (2.1 ng/mL and 1.7 ng/mL, respectively) as well as in the psoas major muscle (1.2 ng/g). Higher concentrations were found in the lung (2.6 ng/g), liver (2.6 ng/g), and kidney (3.8 ng/g). Gastric content yielded a MDMB-CHMICA concentration of 2.4 ng/g (1.1 μg absolute). Screening for MDMB-CHMICA metabolites resulted in the detection of mainly monohydroxylated metabolites in the blood, kidney, and liver specimens. Results indicated that monohydroxylated metabolites of MDMB-CHMICA are appropriate target analytes for detecting MDMB-CHMICA intake.

Pharmacokinetic Profile of Oral Cannabis in Humans: Blood and Oral Fluid Disposition and Relation to Pharmacodynamic Outcomes

Most research on cannabis pharmacokinetics has evaluated inhaled cannabis, but oral ("edible") preparations comprise an increasing segment of the cannabis market. To assess oral cannabis pharmacokinetics and pharmacodynamics, healthy adults (N = 6 per dose) were administered cannabis brownies containing 10, 25 or 50 mg 9-tetrahydrocannabinol (THC). Whole blood and oral fluid specimens were obtained at baseline and then for 9 days post-exposure; 6 days in a residential research setting and 3 days as outpatients. Measures of subjective, cardiovascular and performance effects were obtained at baseline and for 8 h post-ingestion. The mean Cmax for THC in whole blood was 1, 3.5 and 3.3 ng/mL for the 10, 25 and 50 mg THC doses, respectively. The mean maximum concentration (Cmax) and mean time to maximum concentration (Tmax) of 11-OH-THC in whole blood were similar to THC. Cmax blood concentrations of THCCOOH were generally higher than THC and had longer Tmax values. The mean Tmax for THC in oral fluid occurred immediately following oral dose administration, and appear to reflect local topical residue rather than systemic bioavailbility. Mean Cmax oral fluid concentrations of THCCOOH were lower than THC, erratic over time and mean Tmax occurred at longer times than THC. The window of THC detection ranged from 0 to 22 h for whole blood (limit of quantitation (LOQ) = 0.5 ng/mL) and 1.9 to 22 h for oral fluid (LOQ = 1.0 ng/mL). Subjective drug and cognitive performance effects were generally dose dependent, peaked at 1.5-3 h post-administration, and lasted 6-8 h. Whole blood cannabinoid concentrations were significantly correlated with subjective drug effects. Correlations between blood cannabinoids and cognitive performance measures, and between oral fluid and all pharmacodynamic outcomes were either non-significant or not orderly by dose. Quantitative levels of cannabinoids in whole blood and oral fluid were low compared with levels observed following inhalation of cannabis. The route of administration is important for interpretation of cannabinoid toxicology.

Psychiatric and medical management of marijuana intoxication in the emergency department

We use a case report to describe the acute psychiatric and medical management of marijuana intoxication in the emergency setting. A 34-year-old woman presented with erratic, disruptive behavior and psychotic symptoms after recreational ingestion of edible cannabis. She was also found to have mild hypokalemia and QT interval prolongation. Psychiatric management of cannabis psychosis involves symptomatic treatment and maintenance of safety during detoxification. Acute medical complications of marijuana use are primarily cardiovascular and respiratory in nature; electrolyte and electrocardiogram monitoring is indicated. This patient's psychosis, hypokalemia and prolonged QTc interval resolved over two days with supportive treatment and minimal intervention in the emergency department. Patients with cannabis psychosis are at risk for further psychotic sequelae. Emergency providers may reduce this risk through appropriate diagnosis, acute treatment, and referral for outpatient care.

Long-term effects of cannabis on brain structure

The dose-dependent toxicity of the main psychoactive component of cannabis in brain regions rich in cannabinoid CB1 receptors is well known in animal studies. However, research in humans does not show common findings across studies regarding the brain regions that are affected after long-term exposure to cannabis. In the present study, we investigate (using Voxel-based Morphometry) gray matter changes in a group of regular cannabis smokers in comparison with a group of occasional smokers matched by the years of cannabis use. We provide evidence that regular cannabis use is associated with gray matter volume reduction in the medial temporal cortex, temporal pole, parahippocampal gyrus, insula, and orbitofrontal cortex; these regions are rich in cannabinoid CB1 receptors and functionally associated with motivational, emotional, and affective processing. Furthermore, these changes correlate with the frequency of cannabis use in the 3 months before inclusion in the study. The age of onset of drug use also influences the magnitude of these changes. Significant gray matter volume reduction could result either from heavy consumption unrelated to the age of onset or instead from recreational cannabis use initiated at an adolescent age. In contrast, the larger gray matter volume detected in the cerebellum of regular smokers without any correlation with the monthly consumption of cannabis may be related to developmental (ontogenic) processes that occur in adolescence.