The anxiolytic effects of cannabidiol in chronically stressed mice are mediated by the endocannabinoid system: Role of neurogenesis and dendritic remodeling

The anxiolytic effects of cannabinoids: A comprehensive review

Cannabinoids, notably cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC), have emerged as promising candidates for anxiety disorder treatment, supported by both preclinical and clinical evidence. CBD exhibits notable anxiolytic effects with a favourable safety profile, though concerns regarding mild side effects and drug interactions remain. Conversely, THC, the primary psychoactive compound, presents a range of side effects, underscoring the importance of careful dosage management and individualized treatment strategies. So far there are no FDA approved cannabinoid medications for anxiety. The review highlights challenges in cannabinoid research, including dosage variability, variable preclinical data, and limited long-term data. Despite these limitations, cannabinoids represent a promising avenue for anxiety management, with the potential for further optimization in formulation, dosing protocols, and consideration of interactions with conventional therapies. Addressing these challenges could pave the way for novel and personalized approaches to treating anxiety disorders using cannabinoid-based therapies.

The interaction between cannabinoids and long-term synaptic plasticity: A survey on memory formation and underlying mechanisms

Synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD), is an essential phenomenon in memory formation as well as maintenance along with many other cognitive functions, such as those needed for coping with external stimuli. Synaptic plasticity consists of gradual changes in the biochemistry and morphology of pre- and postsynaptic neurons, particularly in the hippocampus. Consuming marijuana as a primary source of exocannabinoids immediately impairs attention and working memory-related tasks. Evidence regarding the effects of cannabinoids on LTP and memory is contradictory. While cannabinoids can affect a variety of specific cannabinoid receptors (CBRs) and nonspecific receptors throughout the body and brain, they exert miscellaneous systemic and local cerebral effects. Given the increasing use of cannabis, mainly among the young population, plus its potential adverse long-term effects on learning and memory processes, it could be a future global health challenge. Indeed, the impact of cannabinoids on memory is multifactorial and depends on the dosage, timing, formula, and route of consumption, plus the background complex interaction of the endocannabinoids system with other cerebral networks. Herein, we review how exogenously administrated organic cannabinoids, CBRs agonists or antagonists, and endocannabinoids can affect LTP and synaptic plasticity through various receptors in interaction with other cerebral pathways and primary neurotransmitters.

New insights into the involvement of serotonin and BDNF-TrkB signalling in cannabidiol's antidepressant effect

Cannabidiol (CBD) is a phytocannabinoid devoid of psychostimulant properties and is currently under investigation as a potential antidepressant drug. However, the mechanisms underlying CBD's antidepressant effects are not yet well understood. CBD targets include a variety of receptors, enzymes, and transporters, with different binding-affinities. Neurochemical and pharmacological evidence indicates that both serotonin and BDNF-TrkB signalling in the prefrontal cortex are necessary for the antidepressant effects induced by CBD in animal models. Herein, we reviewed the current literature to dissect if these are independent mechanisms or if CBD-induced modulation of the serotonergic neurotransmission could mediate its neuroplastic effects through subsequent regulation of BDNF-TrkB signalling, thus culminating in rapid neuroplastic changes. It is hypothesized that: a) CBD interaction with serotonin receptors on neurons of the dorsal raphe nuclei and the resulting disinhibition of serotonergic neurons would promote rapid serotonin release in the PFC and hence its neuroplastic and antidepressant effects; b) CBD facilitates BDNF-TRKB signalling, especially in the PFC, which rapidly triggers neurochemical and neuroplastic effects. These hypotheses are discussed with perspectives for new drug development and clinical applications.

Therapeutic potential of CBD in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterized by persistent deficits in social communication and interaction, as well as restricted and repetitive patterns of behavior. Despite extensive research, effective pharmacological interventions for ASD remain limited. Cannabidiol (CBD), a non-psychotomimetic compound of the Cannabis sativa plant, has potential therapeutic effects on several neurological and psychiatric disorders. CBD interacts with the endocannabinoid system, a complex cell-signaling system that plays a crucial role in regulating various physiological processes, maintaining homeostasis, participating in social and behavioral processing, and neuronal development and maturation with great relevance to ASD. Furthermore, preliminary findings from clinical trials indicate that CBD may have a modulatory effect on specific ASD symptoms and comorbidities in humans. Interestingly, emerging evidence suggests that CBD may influence the gut microbiota, with implications for the bidirectional communication between the gut and the central nervous system. CBD is a safe drug with low induction of side effects. As it has a multi-target pharmacological profile, it becomes a candidate compound for treating the central symptoms and comorbidities of ASD.

Historical perspective on the therapeutic potential of cannabidiol

Cannabidiol (CBD) is one of over 200 cannabinoids present in the Cannabis plant. Unlike the plant's primary cannabinoid, delta-9-tetrahydrocannabinol (THC), CBD does not produce psychotomimetic effects nor induce dependence. Initially considered an inactive cannabinoid, interest in its pharmacological properties and therapeutic potential has grown exponentially over the last 20 years. Currently employed as a medication for certain epileptic syndromes, numerous pre-clinical and clinical studies support its potential use in various other disorders. In this chapter, we provide a brief historical overview of how this compound evolved from an "inactive substance" to a multifunctional clinical agent. Additionally, we discuss the current challenges in researching its potential therapeutic effects.

Therapeutic potential of cannabidiol in depression

Major depressive disorder (MDD) is a widespread and debilitating condition affecting a significant portion of the global population. Traditional treatment for MDD has primarily involved drugs that increase brain monoamines by inhibiting their uptake or metabolism, which is the basis for the monoaminergic hypothesis of depression. However, these treatments are only partially effective, with many patients experiencing delayed responses, residual symptoms, or complete non-response, rendering the current view of the hypothesis as reductionist. Cannabidiol (CBD) has shown promising results in preclinical models and human studies. Its mechanism is not well-understood, but may involve monoamine and endocannabinoid signaling, control of neuroinflammation and enhanced neuroplasticity. This chapter will explore CBD's effects in preclinical and clinical studies, its molecular mechanisms, and its potential as a treatment for MDD.

4'-fluorocannabidiol associated with capsazepine restrains L-DOPA-induced dyskinesia in hemiparkinsonian mice: Contribution of anti-inflammatory and anti-glutamatergic mechanisms

We tested the efficacy of 4'-fluorocannabidiol (4'-F-CBD), a semisynthetic cannabidiol derivative, and HU-910, a cannabinoid receptor 2 (CB2) agonist in resolving l-DOPA-induced dyskinesia (LID). Specifically, we were interested in studying whether these compounds could restrain striatal inflammatory responses and rescue glutamatergic disturbances characteristic of the dyskinetic state. C57BL/6 mice were rendered hemiparkinsonian by unilateral striatal lesioning with 6-OHDA. Abnormal involuntary movements were then induced by repeated i.p. injections of l-DOPA + benserazide. After LID was installed, the effects of a 3-day treatment with 4'-F-CBD or HU-910 in combination or not with the TRPV1 antagonist capsazepine (CPZ) or CB2 agonists HU-308 and JWH015 were assessed. Immunostaining was conducted to investigate the impacts of 4'-F-CBD and HU-910 (with CPZ) on inflammation and glutamatergic synapses. Our results showed that the combination of 4'-F-CBD + CPZ, but not when administered alone, decreased LID. Neither HU-910 alone nor HU-910+CPZ were effective. The CB2 agonists HU-308 and JWH015 were also ineffective in decreasing LID. Both combination treatments efficiently reduced microglial and astrocyte activation in the dorsal striatum of dyskinetic mice. However, only 4'-F-CBD + CPZ normalized the density of glutamate vesicular transporter-1 (vGluT1) puncta colocalized with the postsynaptic density marker PSD95. These findings suggest that 4'-F-CBD + CPZ normalizes dysregulated cortico-striatal glutamatergic inputs, which could be involved in their anti-dyskinetic effects. Although it is not possible to rule out the involvement of anti-inflammatory mechanisms, the decrease in striatal neuroinflammation markers by 4'-F-CBD and HU-910 without an associated reduction in LID indicates that they are insufficient per se to prevent LID manifestations.

Endocannabinoid Hydrolase Inhibitors: Potential Novel Anxiolytic Drugs

Over the past decade, the idea of targeting the endocannabinoid system to treat anxiety disorders has received increasing attention. Previous studies focused more on developing cannabinoid receptor agonists or supplementing exogenous cannabinoids, which are prone to various adverse effects due to their strong pharmacological activity and poor receptor selectivity, limiting their application in clinical research. Endocannabinoid hydrolase inhibitors are considered to be the most promising development strategies for the treatment of anxiety disorders. More recent efforts have emphasized that inhibition of two major endogenous cannabinoid hydrolases, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), indirectly activates cannabinoid receptors by increasing endogenous cannabinoid levels in the synaptic gap, circumventing receptor desensitization resulting from direct enhancement of endogenous cannabinoid signaling. In this review, we comprehensively summarize the anxiolytic effects of MAGL and FAAH inhibitors and their potential pharmacological mechanisms, highlight reported novel inhibitors or natural products, and provide an outlook on future directions in this field.

Repeated cannabidiol treatment affects neuroplasticity and endocannabinoid signaling in the prefrontal cortex of the Flinders Sensitive Line (FSL) rat model of depression

Delayed therapeutic responses and limited efficacy are the main challenges of existing antidepressant drugs, thereby incentivizing the search for new potential treatments. Cannabidiol (CBD), non-psychotomimetic component of cannabis, has shown promising antidepressant effects in different rodent models, but its mechanism of action remains unclear. Herein, we investigated the antidepressant-like effects of repeated CBD treatment on behavior, neuroplasticity markers and lipidomic profile in the prefrontal cortex (PFC) of Flinders Sensitive Line (FSL), a genetic animal model of depression, and their control counterparts Flinders Resistant Line (FRL) rats. Male FSL animals were treated with CBD (10 mg/kg; i.p.) or vehicle (7 days) followed by Open Field Test (OFT) and the Forced Swimming Test (FST). The PFC was analyzed by a) western blotting to assess markers of synaptic plasticity and cannabinoid signaling in synaptosome and cytosolic fractions; b) mass spectrometry-based lipidomics to investigate endocannabinoid levels (eCB). CBD attenuated the increased immobility observed in FSL, compared to FRL in FST, without changing the locomotor behavior in the OFT. In synaptosomes, CBD increased ERK1, mGluR5, and Synaptophysin, but failed to reverse the reduced CB1 and CB2 levels in FSL rats. In the cytosolic fraction, CBD increased ERK2 and decreased mGluR5 expression in FSL rats. Surprisingly, there were no significant changes in eCB levels in response to CBD treatment. These findings suggest that CBD effects in FSL animals are associated with changes in synaptic plasticity markers involving mGluR5, ERK1, ERK2, and synaptophysin signaling in the PFC, without increasing the levels of endocannabinoids in this brain region.

Therapeutic applicability of cannabidiol and other phytocannabinoids in epilepsy, multiple sclerosis and Parkinson's disease and in comorbidity with psychiatric disorders

Studies have demonstrated the neuroprotective effect of cannabidiol (CBD) and other Cannabis sativa L. derivatives on diseases of the central nervous system caused by their direct or indirect interaction with endocannabinoid system-related receptors and other molecular targets, such as the 5-HT1A receptor, which is a potential pharmacological target of CBD. Interestingly, CBD binding with the 5-HT1A receptor may be suitable for the treatment of epilepsies, parkinsonian syndromes and amyotrophic lateral sclerosis, in which the 5-HT1A serotonergic receptor plays a key role. The aim of this review was to provide an overview of cannabinoid effects on neurological disorders, such as epilepsy, multiple sclerosis and Parkinson's diseases, and discuss their possible mechanism of action, highlighting interactions with molecular targets and the potential neuroprotective effects of phytocannabinoids. CBD has been shown to have significant therapeutic effects on epilepsy and Parkinson's disease, while nabiximols contribute to a reduction in spasticity and are a frequent option for the treatment of multiple sclerosis. Although there are multiple theories on the therapeutic potential of cannabinoids for neurological disorders, substantially greater progress in the search for strong scientific evidence of their pharmacological effectiveness is needed.

A Novel Anti-Inflammatory Formulation Comprising Celecoxib and Cannabidiol Exerts Antidepressant and Anxiolytic Effects

Background: Ample research shows that anti-inflammatory drugs, particularly celecoxib, exert antidepressant effects, especially in patients with microglia activation. However, substantial cardiovascular adverse effects limit celecoxib's usefulness. Given that cannabidiol (CBD) exerts anti-inflammatory, microglia-suppressive, and antidepressant effects, we hypothesized that it may potentiate the therapeutic effects of celecoxib. Methods: The effects of celecoxib, CBD, and their combination were examined in murine models of antidepressant- and anxiolytic-like behavioral responsiveness, including the forced swim test (FST), elevated plus maze (EPM), lipopolysaccharide (LPS)-induced neuroinflammation, and chronic social defeat stress (CSDS), as well as in microglia cell cultures. Results: Acute administration of a combination of celecoxib plus CBD, at doses that had no effects by themselves (10 and 5 mg/kg, respectively), produced significant antidepressant- and anxiolytic-like effects in the FST and EPM, in male and female mice. In the LPS model, combinations of celecoxib (10 or 20 mg/kg) plus CBD (30 mg/kg) reversed the anxiety-like behavior in the open-field test (OFT) and anhedonia in the sucrose preference test (SPT), with minimal effects of celecoxib or CBD by themselves. In the CSDS paradigm, a combination of celecoxib plus CBD (each at 30 mg/kg) reversed the deficits in the OFT, EPM, social exploration, and SPT, whereas celecoxib or CBD by themselves had partial effects. In BV2 microglia cultures stimulated with LPS or α-synuclein, CBD markedly potentiated the suppressive effects of celecoxib over TNFα (tumor necrosis factor-α) and IL (interleukin)-1β secretion. Conclusions: Combinations of celecoxib plus CBD produce efficacious antidepressant- and anxiolytic-like effects, which may depend on their synergistic microglia-suppressive effects.

Cannabinoid type 2 receptor inhibition enhances the antidepressant and proneurogenic effects of physical exercise after chronic stress

Chronic stress is a major risk factor for neuropsychiatric conditions such as depression. Adult hippocampal neurogenesis (AHN) has emerged as a promising target to counteract stress-related disorders given the ability of newborn neurons to facilitate endogenous plasticity. Recent data sheds light on the interaction between cannabinoids and neurotrophic factors underlying the regulation of AHN, with important effects on cognitive plasticity and emotional flexibility. Since physical exercise (PE) is known to enhance neurotrophic factor levels, we hypothesised that PE could engage with cannabinoids to influence AHN and that this would result in beneficial effects under stressful conditions. We therefore investigated the actions of modulating cannabinoid type 2 receptors (CB2R), which are devoid of psychotropic effects, in combination with PE in chronically stressed animals. We found that CB2R inhibition, but not CB2R activation, in combination with PE significantly ameliorated stress-evoked emotional changes and cognitive deficits. Importantly, this combined strategy critically shaped stress-induced changes in AHN dynamics, leading to a significant increase in the rates of cell proliferation and differentiation of newborn neurons, overall reduction in neuroinflammation, and increased hippocampal levels of BDNF. Together, these results show that CB2Rs are crucial regulators of the beneficial effects of PE in countering the effects of chronic stress. Our work emphasises the importance of understanding the mechanisms behind the actions of cannabinoids and PE and provides a framework for future therapeutic strategies to treat stress-related disorders that capitalise on lifestyle interventions complemented with endocannabinoid pharmacomodulation.

Cannabidiol modulates hippocampal genes involved in mitochondrial function, ribosome biogenesis, synapse organization, and chromatin modifications

BACKGROUND

Cannabidiol (CBD) is one of the main cannabinoids present in Cannabis sativa female flowers. Previous investigation has already provided insights into the CBD molecular mechanism; however, there is no transcriptome data for CBD effects on hippocampal subfields. Here, we investigate transcriptomic changes in dorsal and ventral CA1 of adult mice hippocampus after 100 mg/kg of CBD administration (i.p.) for one or seven consecutive days.

METHODS

C57BL/6JUnib mice were treated with either vehicle or CBD for 1 or 7 days. The collected brains were sectioned, and the hippocampal sub-regions were laser microdissected for RNA-Seq analysis.

RESULTS

The transcriptome analysis following 7 days of CBD administration indicates the differential expression of 1559 genes in dCA1 and 2924 genes in vCA1. Furthermore, GO/KEGG analysis identified 88 significantly enriched biological process and 26 significantly enriched pathways for dCBD7, whereas vCBD7 revealed 128 enriched BPs and 24 pathways.

CONCLUSION

This dataset indicates a widespread decrease of electron transport chain and ribosome biogenesis transcripts in CA1, while chromatin modifications and synapse organization transcripts were increased following CBD administration for 7 days.

Effects of acute cannabidiol on behavior and the endocannabinoid system in HIV-1 Tat transgenic female and male mice

Background

Some evidence suggests that cannabidiol (CBD) has potential to help alleviate HIV symptoms due to its antioxidant and anti-inflammatory properties. Here we examined acute CBD effects on various behaviors and the endocannabinoid system in HIV Tat transgenic mice.

Methods

Tat transgenic mice (female/male) were injected with CBD (3, 10, 30 mg/kg) and assessed for antinociception, activity, coordination, anxiety-like behavior, and recognition memory. Brains were taken to quantify endocannabinoids, cannabinoid receptors, and cannabinoid catabolic enzymes. Additionally, CBD and metabolite 7-hydroxy-CBD were quantified in the plasma and cortex.

Results

Tat decreased supraspinal-related nociception and locomotion. CBD and sex had little to no effects on any of the behavioral measures. For the endocannabinoid system male sex was associated with elevated concentration of the proinflammatory metabolite arachidonic acid in various CNS regions, including the cerebellum that also showed higher FAAH expression levels for Tat(+) males. GPR55 expression levels in the striatum and cerebellum were higher for females compared to males. CBD metabolism was altered by sex and Tat expression.

Conclusion

Findings indicate that acute CBD effects are not altered by HIV Tat, and acute CBD has no to minimal effects on behavior and the endocannabinoid system.

Behavioral observations, heart rate and cortisol monitoring in horses following multiple oral administrations of a cannabidiol containing paste (part 2/2)

As a remedy against stress and anxiety, cannabidiol (CBD) products are of increasing interest in veterinary medicine. Limited data is available describing the actual effectiveness of CBD in horses. The aim of this study (part 2 of 2) was to analyze stress parameters via behavioral observation, heart rate monitoring and assessment of blood and saliva cortisol levels in healthy horses treated repeatedly with a CBD containing paste. Twelve horses were randomly assigned to a treatment or a control group. Two pastes were orally administered in a double-blinded study design, one paste containing CBD and one paste without active ingredient. Both pastes were administered twice daily over 15 days (dose: 3 mg CBD/kg). Behavioral observations were conducted daily using a sedation score and a rating of facial expressions, based on the previously described facial sedation scale for horses (FaceSed) and the Horse Grimace Scale. Blood and saliva samples were obtained regularly to determine cortisol levels throughout the study. Cortisol levels were analyzed by means of liquid chromatography/tandem mass spectrometry (LC/MS/MS). Behavioral observations and cortisol levels were compared between groups. Prior to paste administration, a novel object test was performed and the horses' reaction to loading on a trailer was recorded. Both tests were repeated after 13 days of paste application. Movement patterns such as different gaits during the novel object test were evaluated and an ethogram was designed to assess exhibited behavioral traits. Cardiac beat-to-beat (R-R) intervals were recorded throughout and evaluated using heart rate (HR) and heart rate variability (HRV) parameters. Blood and saliva samples for cortisol analysis were taken before and after the tests. Daily behavioral observations and cortisol levels did not differ between the treatment and the control group. Similarly, analysis of movement patterns, HR, HRV and cortisol levels during the novel object test and trailer test did not identify significant differences between the groups. Regularly administered oral CBD (3 mg/kg BID over 15 days) had no statistically significant effect on behavioral observations, cortisol levels, HR and HRV in horses. Further research is required to establish adequate doses and indications for the use of CBD in horses.

An Overview of Cannabidiol

Cannabidiol (CBD) is one of the most interesting constituents of cannabis, garnering significant attention in the medical community in recent years due to its proven benefit for reducing refractory seizures in pediatric patients. Recent legislative changes in the United States have made CBD readily available to the general public, with up to 14% of adults in the United States having tried it in 2019. CBD is used to manage a myriad of symptoms, including anxiety, pain, and sleep disturbances, although rigorous evidence for these indications is lacking. A significant advantage of CBD over the other more well-known cannabinoid delta-9-tetrahydroncannabinol (THC) is that CBD does not produce a "high." As patients increasingly self-report its use to manage their medical conditions, and as the opioid epidemic continues to drive the quest for alternative pain management approaches, the aims of this narrative review are to provide a broad overview of the discovery, pharmacology, and molecular targets of CBD, its purported and approved neurologic indications, evidence for its analgesic potential, regulatory implications for patients and providers, and future research needs.

Anxiogenic doses of rapamycin prevent URB597-induced anti-stress effects in socially defeated mice

Repeated exposure to psychosocial stress modulates the endocannabinoid system, particularly anandamide (AEA) signaling in brain regions associated with emotional distress. The mTOR protein regulates various neuroplastic processes in the brain disrupted by stress, including adult hippocampal neurogenesis. This kinase has been implicated in multiple effects of cannabinoid drugs and the anti-stress behavioral effects of psychoactive drugs. Therefore, our hypothesis is that enhancing AEA signaling via pharmacological inhibition of the fatty acid amide hydrolase (FAAH) enzyme induces an anti-stress behavioral effect through an mTOR-dependent mechanism. To test this hypothesis, male C57Bl6 mice were exposed to social defeat stress (SDS) for 7 days and received daily treatment with either vehicle or different doses of the FAAH inhibitor, URB597 (0.1; 0.3; 1 mg/Kg), alone or combined with rapamycin. The results suggested that URB597 induced an inverted U-shaped dose-response curve in mice subjected to SDS (with the intermediate dose of 0.3 mg/kg being anxiolytic, and the higher tested dose of 1 mg/Kg being anxiogenic). In a second independent experiment, rapamycin treatment induced an anxiogenic-like response in control mice. However, in the presence of rapamycin, the anxiolytic dose of URB597 treatment failed to reduce stress-induced anxiety behaviors in mice. SDS exposure altered the hippocampal expression of the mTOR scaffold protein Raptor. Furthermore, the anxiogenic dose of URB597 decreased the absolute number of migrating doublecortin (DCX)-positive cells in the dentate gyrus, suggesting an anti-anxiety effect independent of newly generated/immature neurons. Therefore, our results indicate that in mice exposed to repeated psychosocial stress, URB597 fails to counteract the anxiogenic-like response induced by the pharmacological dampening of mTOR signaling.

Behavioral observations, heart rate and heart rate variability in horses following oral administration of a cannabidiol containing paste in three escalating doses (part 1/2)

Cannabidiol (CBD) products have been proposed to exert stress- and anxiety-relieving effects in animals. Despite the increasing popularity of CBD for veterinary use, the available research detailing the effects of CBD in horses is limited. The aim of this study (part 1 of 2) was to analyze stress parameters via behavioral observations and heart rate monitoring in healthy horses following single oral administration of a CBD containing paste in different doses. Study products were two pastes for oral administration, one containing CBD and one containing no active ingredient. Pastes were applied as single administrations in consecutive trials with escalating dosages (doses: 0.2, 1.0, 3.0 mg CBD/kg) to a treatment (trial 1: n = 3, trial 2: n = 3, trial 3: n = 5 horses) and a control group (trial 1: n = 3, trial 2: n = 3, trial 3: n = 6 horses) with minimum wash-out periods of seven days in between. Behavioral parameters were evaluated using video recordings to score the levels of sedation including the horses' reactions to acoustic and visual stimuli. Facial expression was assessed using photographs. Evaluation was based on the previously described facial sedation scale for horses (FaceSed) and the Horse Grimace Scale. For baseline values, identical observations were recorded on the day before each paste administration. Both paste administration and behavioral evaluation were performed double blinded. Cardiac beat-to-beat (R-R) intervals were continuously recorded throughout the trial and assessed using heart rate and heart rate variability parameters. Statistical analysis included comparison between treatment and control group over escalating doses and time points using linear mixed models. The CBD paste was well tolerated, and no side effects were observed. Analysis of sedation scores and facial expressions did not indicate significant differences between treatment and control group over the escalating doses. The heart rate was neither reduced, nor were significant changes in heart rate variability observed compared to the control group. Main limitation of this study is the small sample size. Further research is required to determine adequate doses and indications for the use of CBD products in horses.

Sex and estrous cycle-linked differences in the effect of cannabidiol on panic-like responding in rats and mice

Clinical and preclinical studies point towards anxiolytic actions of cannabidiol (CBD), but its effect in panic disorder has been less explored and few studies consider effects in females. We here compared the effect of CBD on the response of male and female rats and mice to a panicogenic challenge; exposure to low O2 (rats) or high CO2 (mice) paying attention in females to possible effects of estrous cycle phase. Male and female Sprague-Dawley rats and C57BL/6 J mice were exposed to 7% O2 for 5 min (rats) or 20% CO2 (mice) and escape behaviour, which has been associated with panic attacks, was quantified as undirected jumps towards the gas chamber's ceiling. The effect of pretreatment with CBD (1-10 mg kg-1 i.p. in rats or 10-60 mg kg-1 i.p. in mice) was tested. The results showed that low O2 (rats) or high CO2 (mice) evoked escape in both sexes. In female rats the response was estrous cycle-sensitive: females in late diestrus made significantly more jumps than females in proestrus. In female mice escape was not influenced by estrous cycle phase and CBD was panicolytic. In female rats CBD attenuated escape behaviour in late diestrus phase but not in proestrus. In male rats and mice CBD had no effect on escape behaviour. Therefore, CBD is panicolytic in female rats and mice but not in males. In rats the effect is estrous cycle-sensitive: rats were most responsive to CBD in late diestrus. In mice higher doses were required to elicit effects and estrous cycle had no effect.

M1 acetylcholine receptors in somatostatin interneurons contribute to GABAergic and glutamatergic plasticity in the mPFC and antidepressant-like responses

Alterations in glutamatergic and GABAergic function in the medial prefrontal cortex (mPFC) are prevalent in individuals with major depressive disorder, resulting in impaired synaptic plasticity that compromises the integrity of signal transfer to limbic regions. Scopolamine, a non-selective muscarinic receptor antagonist, produces rapid antidepressant-like effects by targeting M1-type acetylcholine receptors (M1R) on somatostatin (SST) interneurons. So far, these effects have been investigated with relatively short-term manipulations, and long-lasting synaptic mechanisms involved in these responses are still unknown. Here, we generated mice with conditional deletion of M1R (M1f/fSstCre+) only in SST interneurons to determine the role of M1R in modulating long-term GABAergic and glutamatergic plasticity in the mPFC that leads to attenuation of stress-relevant behaviors. We have also investigated whether the molecular and antidepressant-like effects of scopolamine could be mimicked or occluded in male M1f/fSstCre+ mice. M1R deletion in SST-expressing neurons occluded the rapid and sustained antidepressant-like effects of scopolamine, as well as scopolamine-induced increases in c-Fos+/CaMKIIα cells and proteins necessary for glutamatergic and GABAergic function in the mPFC. Importantly, M1R SST deletion resulted in resilience to chronic unpredictable stress in behaviors relevant to coping strategies and motivation, and to a lesser extent, in behaviors relevant to avoidance. Finally, M1R SST deletion also prevented stress-induced impairments in the expression of GABAergic and glutamatergic markers in the mPFC. These findings suggest that the antidepressant-like effects of scopolamine result from modulation of excitatory and inhibitory plasticity via M1R blockade in SST interneurons. This mechanism could represent a promising strategy for antidepressant development.

Long-Term Treatment with Cannabidiol-Enriched Cannabis Extract Induces Synaptic Changes in the Adolescent Rat Hippocampus

The endocannabinoid system (eCS) is widely distributed in mammalian tissues and it is classically formed by cannabinoid receptors, endogenous bioactive lipids and its synthesis and degradation enzymes. Due to the modulatory role of eCS in synaptic activity in the Central Nervous System (CNS), phytocannabinoids have been increasingly used for the treatment of neurological disorders, even though little is known in terms of the long-term effect of these treatments on CNS development, mainly in the timeframe that comprises childhood and adolescence. Furthermore, an increased number of clinical trials using full-spectrum Cannabis extracts has been seen, rather than the isolated form of phytocannabinoids, when exploring the therapeutical benefits of the Cannabis plant. Thus, this study aims to evaluate the effect of cannabidiol (CBD)-enriched Cannabis extract on synaptic components in the hippocampus of rats from adolescence to early adulthood (postnatal day 45 to 60). Oral treatment of healthy male Wistar rats with a CBD-enriched Cannabis extract (3 mg/kg/day CBD) during 15 days did not affect food intake and water balance. There was also no negative impact on locomotor behaviour and cognitive performance. However, the hippocampal protein levels of GluA1 and GFAP were reduced in animals treated with the extract, whilst PSD95 levels were increased, which suggests rearrangement of glutamatergic synapses and modulation of astrocytic features. Microglial complexity was reduced in CA1 and CA3 regions, but no alterations in their phagocytic activity have been identified by Iba-1 and LAMP2 co-localization. Collectively, our data suggest that CBD-enriched Cannabis treatment may be safe and well-tolerated in healthy subjects, besides acting as a neuroprotective agent against hippocampal alterations related to the pathogenesis of excitatory and astrogliosis-mediated disorders in CNS.

Anxiolytic effects of endocannabinoid enhancing compounds: A systematic review and meta-analysis

The endocannabinoid system is a promising candidate for anxiolytic therapy, but translation to the clinic has been lagging. We meta-analyzed the evidence for anxiety-reduction by compounds that facilitate endocannabinoid signaling in humans and animals. To identify areas of specific potential, effects of moderators were assessed. Literature was searched in Pubmed and Embase up to May 2021. A placebo/vehicle-control group was required and in human studies, randomization. We excluded studies that co-administered other substances. Risk of bias was assessed with SYRCLE's RoB tool and Cochrane RoB 2.0. We conducted three-level random effects meta-analyses and explored sources of heterogeneity using Bayesian regularized meta-regression (BRMA). The systematic review yielded 134 studies. We analyzed 120 studies (114 animal, 6 human) that investigated cannabidiol (CBD, 61), URB597 (39), PF-3845 (6) and AM404 (14). Pooled effects on conditioned and unconditioned anxiety in animals (with the exception of URB597 on unconditioned anxiety) and on experimentally induced anxiety in humans favored the investigational drugs over placebo/vehicle. Publication year was negatively associated with effects of CBD on unconditioned anxiety. Compared to approach avoidance tests, tests of repetitive-compulsive behavior were associated with larger effects of CBD and URB597, and the social interaction test with smaller effects of URB597. Larger effects of CBD on unconditioned anxiety were observed when anxiety pre-existed. Studies reported few side effects at therapeutic doses. The evidence quality was low with indications of publication bias. More clinical trials are needed to translate the overall positive results to clinical applications.

Endocannabinoid signaling in adult hippocampal neurogenesis: A mechanistic and integrated perspective

Dentate gyrus of the hippocampus continuously gives rise to new neurons, namely, adult-born granule cells, which contribute to conferring plasticity to the mature brain throughout life. Within this neurogenic region, the fate and behavior of neural stem cells (NSCs) and their progeny result from a complex balance and integration of a variety of cell-autonomous and cell-to-cell-interaction signals and underlying pathways. Among these structurally and functionally diverse signals, there are endocannabinoids (eCBs), the main brain retrograde messengers. These pleiotropic bioactive lipids can directly and/or indirectly influence adult hippocampal neurogenesis (AHN) by modulating, both positively and negatively, multiple molecular and cellular processes in the hippocampal niche, depending on the cell type or stage of differentiation. Firstly, eCBs act directly as cell-intrinsic factors, cell-autonomously produced by NSCs following their stimulation. Secondly, in many, if not all, niche-associated cells, including some local neuronal and nonneuronal elements, the eCB system indirectly modulates the neurogenesis, linking neuronal and glial activity to regulating distinct stages of AHN. Herein, we discuss the crosstalk of the eCB system with other neurogenesis-relevant signal pathways and speculate how the hippocampus-dependent neurobehavioral effects elicited by (endo)cannabinergic medications are interpretable in light of the key regulatory role that eCBs play on AHN.

Behavioral effects induced by the cannabidiol analogs HU-502 and HU-556

Cannabidiol is a phytocannabinoid that lacks the psychotomimetic properties of Δ9-tetrahydrocannabinol (THC), the main psychoactive Cannabis sativa component. Cannabidiol has several potential therapeutic properties, including anxiolytic, antidepressant, and antipsychotic; however, cannabidiol has low oral bioavailability, which can limit its clinical use. Here, we investigated if two cannabidiol analogs, HU-502 and HU-556, would be more potent than cannabidiol in behavioral tests predictive of anxiolytic, antidepressant, and antipsychotic effects. Different doses (0.01-3 mg/kg; intraperitoneally) of HU-556 and HU-502 were tested in male Swiss mice submitted to the elevated plus maze (EPM), forced swimming test (FST), and amphetamine-induced-prepulse inhibition (PPI) disruption and hyperlocomotion. Cannabidiol is effective in these tests at a dose range of 15-60 mg/kg in mice. We also investigated if higher doses of HU-556 (3 and 10 mg/kg) and HU-502 (10 mg/kg) produced the cannabinoid tetrad (hypolocomotion, catalepsy, hypothermia, and analgesia), which is induced by THC-like compounds. HU-556 (0.1 and 1 mg/kg) increased the percentage of open arm entries (but not time) in the EPM, decreased immobility time in the FST, and attenuated amphetamine-induced PPI disruption. HU-502 (1 and 3 mg/kg) decreased amphetamine-induced hyperlocomotion and PPI impairment. HU-556, at high doses, caused catalepsy and hypolocomotion, while HU-502 did not. These findings suggest that similar to cannabidiol, HU-556 could induce anxiolytic, antidepressant, and antipsychotic-like effects and that HU-502 has antipsychotic properties. These effects were found at a dose range devoid of cannabinoid tetrad effects.

The Chronic Pharmacological Antagonism of the CB1 Receptor is not Involved in the Behavioral Effects of Antidepressants Administered in Mice Submitted to Chronic Unpredictable Stress

Several pieces of evidence suggest that the monoaminergic theory of depression cannot fully explain all behavioral and neuroplastic changes observed after antidepressant chronic treatment. Other molecular targets, such as the endocannabinoid system, have been associated with the chronic effects of these drugs. In the present study, we hypothesized that the behavioral and neuroplastic effects observed after repeated treatment with the antidepressants (AD) Escitalopram (ESC) or venlafaxine (VFX) in chronically stressed mice depend on CB1 receptor activation. Male mice submitted to the chronic unpredictable stress (CUS) paradigm for 21 days were treated with Esc (10mg/kg) or VFX (20mg/kg) once a day in the presence or not of AM251 (0,3mg/kg), a CB₁ receptor antagonist/inverse agonist. At the end of the CUS paradigm, we conducted behavior tests to evaluate depressive- and anxiety-like behaviors. Our results demonstrated that chronic blockade of the CB₁ receptor does not attenuate the antidepressant- or the anxiolytic-like effects of ESC nor VFX. ESC increased the expression of CB₁ in the hippocampus, but AM251 did not change the pro-proliferative effects of ESC in the dentate gyrus or the increased expression of synaptophysin induced by this AD in the hippocampus. Our results suggest that CB₁ receptors are not involved in behavioral and hippocampal neuroplastic effects observed after repeated antidepressant treatment in mice submitted to CUS.

Cannabidiol for the Treatment of Brain Disorders: Therapeutic Potential and Routes of Administration

The use of cannabidiol (CBD) for treating brain disorders has gained increasing interest. While the mechanism of action of CBD in these conditions is still under investigation, CBD has been shown to affect numerous different drug targets in the brain that are involved in brain disorders. Here we review the preclinical and clinical evidence on the potential therapeutic use of CBD in treating various brain disorders. Moreover, we also examine various drug delivery approaches that have been applied to CBD. Due to the slow absorption and low bioavailability with the current oral CBD therapy, more efficient routes of administration to bypass hepatic metabolism, particularly pulmonary delivery, should be considered. Comparison of pharmacokinetic studies of different delivery routes highlight the advantages of intranasal and inhalation drug delivery over other routes of administration (oral, injection, sublingual, buccal, and transdermal) for treating brain disorders. These two routes of delivery, being non-invasive and able to achieve fast absorption and increase bioavailability, are attracting increasing interest for CBD applications, with more research and development expected in the near future.

Activation of ventral hippocampal CB1 receptors inhibits ketamine-induced anxiogenic-like behavior: Alteration of BDNF/c-Fos levels in the mouse hippocampus

Considering the increasing usage of ketamine as a recreational drug with hallucinogenic properties and also scarce studies about receptor systems responsible for its effects, in the present study we aimed to investigate whether the activation of the ventral hippocampal (VH) CB1 cannabinoid receptors affects the anxiety-like behaviors induced by ketamine. Also, the levels of BDNF and c-Fos proteins in the mouse hippocampus were measured following the treatments. For this purpose, male NMRI mice were cannulated bilaterally in the VH with a stereotaxic apparatus. Anxiety properties and protein changes were measured using elevated plus-maze (EPM) and western blotting respectively. The results revealed that intraperitoneal (i.p.) administration of ketamine (5-20 mg/kg) significantly decreased the percentage of open arm time (%OAT) and open arm entry (%OAE) in the EPM with no alteration in the locomotor activity suggesting an anxiogenic-like behavior to ketamine. Furthermore, ketamine administration (10 mg/kg, i.p.) increased BDNF and c-Fos levels in the hippocampus. Interestingly, activation of the VH CB1 receptors by ACPA (0.5-4 ng/mouse) inhibited the anxiogenic-like behaviors produced by ketamine, whereas the microinjection of the same doses of ACPA into VH by itself had no effect on the EPM parameters. Hippocampal levels of BDNF and c-Fos decreased after treatment with combined ketamine with ACPA. These results suggest the therapeutic potency of cannabinoid receptor agonists for ketamine-induced anxiogenic-related responses. This effect might be at least partially mediated by the alteration of BDNF and c-Fos signaling in the hippocampus.

Delayed administration of Trichilia catigua A. Juss. Ethyl-acetate fraction after cerebral ischemia prevents spatial memory deficits, decreases oxidative stress, and impacts neural plasticity in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Trichilia catigua A. Juss (Meliaceae) is used in Brazilian folk medicine to alleviate fatigue and emotional stress and improve memory. Previous studies from our laboratory reported that an ethyl-acetate fraction (EAF) of T. catigua that was given before cerebral ischemia in vivo prevented memory loss and reduced oxidative stress and neuroinflammation. Despite the value of these findings of a neuroprotective effect of T. catigua, treatment that was given immediately before or immediately after ischemia limits its clinical relevance. Thus, unknown is whether T. catigua possesses a specific time window of efficacy (TWE) when administered postischemia.

AIM OF THE STUDY

Given continuity to previous studies, we investigated whether an EAF of T. catigua maintains its neuroprotective properties if treatment begins at different time windows of efficacy after ischemia. We also evaluated, for the first time, whether T. catigua possesses neuroplasticity/neurotrophic properties.

MATERIAL AND METHODS

Rats were subjected to transient global brain ischemia (TGCI) and then given a single dose of the EAF (400 mg/kg) or vehicle (1 ml/kg) orally 1, 4, or 6 h postischemia. The levels of protein PCG, GSH, and GSSG, and activity of SOD and CAT were assayed as markers of oxidative stress on the day after ischemia. In another experiment, naive rats underwent spatial learning training in a radial maze task and then subjected to TGCI. Delayed treatment with the EAF began 4 or 6 h later and continued for 7 days. Retrograde memory performance was assessed 10, 17, and 24 days postischemia. Afterward, brains were examined for neurodegeneration and neuronal dendritic morphology in the hippocampus and cerebral cortex. Another group received the EAF at 4 h of reperfusion, and 4 days later their brains were examined for GFAP and Iba-1 immunoreactivity. Lastly, ischemic rats received the EAF 4 h after ischemia and neural plasticity-related proteins, BDNF, SYN, PSD 95, and NeuN were measured in the hippocampus 7 and 14 days after ischemia.

RESULTS

A single EAF administration 1, 4, or 6 h postischemia alleviated oxidative stress that was caused by ischemia, expressed as a reduction of the amount of the PCG and GSSG, normalization of the GSH/GSSG ratio, and the restoration of SOD activity. Ischemia caused the persistent loss of memory (i.e., amnesia), an outcome that was consistently ameliorated by treatment with the EAF that was initiated 4 or 6 h postischemia. The 4 h delay in EAF treatment positively impacted dendritic morphology in neurons that survived ischemia. TGCI reduced BDNF, SYN, PSD-95, and NeuN protein levels in the hippocampus and cerebral cortex. The EAF normalized SYN and PSD-95 protein levels. Ischemia-induced neurodegeneration and glial cell activation were not prevented by EAF treatment.

CONCLUSION

The present study corroborates prior data that demonstrated the neuroprotective potential of T. catigua and extends these data by showing that the delayed administration of EAF postischemia effectively prevented memory impairment and decreased oxidative stress, dendritic deterioration, and synaptic protein loss within a TWE that ranged from 1 to 6 h. This specific TWE in preclinical research may have clinical relevance by suggesting the possible utility of this plant for the development of neuroprotective strategies in the setting of ischemic brain diseases. Another innovative finding of the present study was the possible neurotrophic/neuroplastic properties of T. catigua.

Effects of repeated lysergic acid diethylamide (LSD) on the mouse brain endocannabinoidome and gut microbiome

BACKGROUND AND PURPOSE

Psychedelics elicit prosocial, antidepressant and anxiolytic effects via neuroplasticity, neurotransmission and neuro-immunomodulatory mechanisms. Whether psychedelics affect the brain endocannabinoid system and its extended version, the endocannabinoidome (eCBome) or the gut microbiome, remains unknown.

EXPERIMENTAL APPROACH

Adult C57BL/6N male mice were administered lysergic acid diethylamide (LSD) or saline for 7 days. Sociability was assessed in the direct social interaction and three chambers tests. Prefrontal cortex and hippocampal endocannabinoids, endocannabinoid-like mediators and metabolites were quantified via high-pressure liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Neurotransmitter levels were assessed via HPLC-UV/fluorescence. Gut microbiome changes were investigated by 16S ribosomal DNA sequencing.

KEY RESULTS

LSD increased social preference and novelty and decreased hippocampal levels of the N-acylethanolamines N-linoleoylethanolamine (LEA), anandamide (N-arachidonoylethanolamine) and N-docosahexaenoylethanolamine (DHEA); the monoacylglycerol 1/2-docosahexaenoylglycerol (1/2-DHG); the prostaglandins D₂ (PGD₂ ) and F2α (PGF_2α ); thromboxane 2 and kynurenine. Prefrontal eCBome mediator and metabolite levels were less affected by the treatment. LSD decreased Shannon alpha diversity of the gut microbiota, prevented the decrease in the Firmicutes:Bacteroidetes ratio observed in saline-treated mice and altered the relative abundance of the bacterial taxa Bifidobacterium, Ileibacterium, Dubosiella and Rikenellaceae RC9.

CONCLUSIONS AND IMPLICATIONS

The prosocial effects elicited by repeated LSD administration are accompanied by alterations of hippocampal eCBome and kynurenine levels, and the composition of the gut microbiota. Modulation of the hippocampal eCBome and kynurenine pathway might represent a mechanism by which psychedelic compounds elicit prosocial effects and affect the gut microbiome.

Cannabidiol repairs behavioral and brain disturbances in a model of fetal alcohol spectrum disorder

Fetal alcohol spectrum disorder (FASD) includes neuropsychiatric disturbances related to gestational and lactational ethanol exposure. Available treatments are minimal and do not modulate ethanol-induced damage. Developing animal models simulating FASD is essential for understanding the underlying brain alterations and searching for efficient therapeutic approaches. The main goal of this study was to evaluate the effects of early and chronic cannabidiol (CBD) administration on offspring exposed to an animal model of FASD. Ethanol gavage (3 g/kg/12 h, p.o.) was administered to C57BL/6 J female mice, with a previous history of alcohol consumption, between gestational day 7 and postnatal day 21. On the weaning day, pups were separated by sex, and CBD administration began (30 mg/kg/day, i.p.). After 4-6 weeks of treatment, behavioral and neurobiological changes were analyzed. Mice exposed to the animal model of FASD showed higher anxiogenic and depressive-like behaviors and cognitive impairment that were evaluated through several experimental tests. These behaviors were accompanied by alterations in the gene, cellular and metabolomic targets. CBD administration normalized FASD model-induced emotional and cognitive disturbances, gene expression, and cellular changes with sex-dependent differences. CBD modulates the metabolomic changes detected in the hippocampus and prefrontal cortex. Interestingly, no changes were found in mitochondria or the oxidative status of the cells. These results suggest that the early and repeated administration of CBD modulated the long-lasting behavioral, gene and protein alterations induced by the FASD model, encouraging the possibility of performing clinical trials to evaluate the effects of CBD in children affected with FASD.

The NLRP3 Inflammasome in Stress Response: Another Target for the Promiscuous Cannabidiol

Many psychiatric patients do not respond to conventional therapy. There is a vast effort to investigate possible mechanisms involved in treatment resistance, trying to provide better treatment options, and several data points toward a possible involvement of inflammatory mechanisms. Microglia, glial, and resident immune cells are involved in complex responses in the brain, orchestrating homeostatic functions, such as synaptic pruning and maintaining neuronal activity. In contrast, microglia play a major role in neuroinflammation, neurodegeneration, and cell death. Increasing evidence implicate microglia dysfunction in neuropsychiatric disorders. The mechanisms are still unclear, but one pathway in microglia has received increased attention in the last 8 years, i.e., the NLRP3 inflammasome pathway. Stress response and inflammation, including microglia activation, can be attenuated by Cannabidiol (CBD). CBD has antidepressant, anti-stress, antipsychotic, anti-inflammatory, and other properties. CBD effects are mediated by direct or indirect modulation of many receptors, enzymes, and other targets. This review will highlight some findings for neuroinflammation and microglia involvement in stress-related psychiatric disorders, particularly addressing the NLRP3 inflammasome pathway. Moreover, we will discuss evidence and mechanisms for CBD effects in psychiatric disorders and animal models and address its potential effects on stress response via neuroinflammation and NLRP3 inflammasome modulation.

Epigenomic and Other Evidence for Cannabis-Induced Aging Contextualized in a Synthetic Epidemiologic Overview of Cannabinoid-Related Teratogenesis and Cannabinoid-Related Carcinogenesis

BACKGROUND

Twelve separate streams of empirical data make a strong case for cannabis-induced accelerated aging including hormonal, mitochondriopathic, cardiovascular, hepatotoxic, immunological, genotoxic, epigenotoxic, disruption of chromosomal physiology, congenital anomalies, cancers including inheritable tumorigenesis, telomerase inhibition and elevated mortality.

METHODS

Results from a recently published longitudinal epigenomic screen were analyzed with regard to the results of recent large epidemiological studies of the causal impacts of cannabis. We also integrate theoretical syntheses with prior studies into these combined epigenomic and epidemiological results.

RESULTS

Cannabis dependence not only recapitulates many of the key features of aging, but is characterized by both age-defining and age-generating illnesses including immunomodulation, hepatic inflammation, many psychiatric syndromes with a neuroinflammatory basis, genotoxicity and epigenotoxicity. DNA breaks, chromosomal breakage-fusion-bridge morphologies and likely cycles, and altered intergenerational DNA methylation and disruption of both the histone and tubulin codes in the context of increased clinical congenital anomalies, cancers and heritable tumors imply widespread disruption of the genome and epigenome. Modern epigenomic clocks indicate that, in cannabis-dependent patients, cannabis advances cellular DNA methylation age by 25-30% at age 30 years. Data have implications not only for somatic but also stem cell and germ line tissues including post-fertilization zygotes. This effect is likely increases with the square of chronological age.

CONCLUSION

Recent epigenomic studies of cannabis exposure provide many explanations for the broad spectrum of cannabis-related teratogenicity and carcinogenicity and appear to account for many epidemiologically observed findings. Further research is indicated on the role of cannabinoids in the aging process both developmentally and longitudinally, from stem cell to germ cell to blastocystoids to embryoid bodies and beyond.

Cannabidiol in clinical and preclinical anxiety research. A systematic review into concentration-effect relations using the IB-de-risk tool

BACKGROUND

Preclinical research suggests that cannabidiol (CBD) may have therapeutic potential in pathological anxiety. Dosing guidelines to inform future human studies are however lacking.

AIM

We aimed to predict the therapeutic window for anxiety-reducing effects of CBD in humans based on preclinical models.

METHODS

We conducted two systematic searches in PubMed and Embase up to August 2021, into pharmacokinetic (PK) and pharmacodynamic (PD) data of systemic CBD exposure in humans and animals, which includes anxiety-reducing and potential side effects. Risk of bias was assessed with SYRCLE's RoB tool and Cochrane RoB 2.0. A control group was an inclusion criterion in outcome studies. In human outcome studies, randomisation was required. We excluded studies that co-administered other substances. We used the IB-de-risk tool for a translational integration of outcomes.

RESULTS

We synthesised data from 87 studies. For most observations (70.3%), CBD had no effect on anxiety outcomes. There was no identifiable relation between anxiety outcomes and drug levels across species. In all species (humans, mice, rats), anxiety-reducing effects seemed to be clustered in certain concentration ranges, which differed between species.

DISCUSSION

A straightforward dosing recommendation was not possible, given variable concentration-effect relations across species, and no consistent linear effect of CBD on anxiety reduction. Currently, these results raise questions about the broad use as a drug for anxiety. Meta-analytic studies are needed to quantitatively investigate drug efficacy, including aspects of anxiety symptomatology. Acute and (sub)chronic dosing studies with integrated PK and PD outcomes are required for substantiated dose recommendations.

Potential Utility of Cannabidiol in Stress-Related Disorders

Background: The endocannabinoid (eCB) system plays an important role in homeostatic regulation of anxiety and stress responses; however, the eCB system can be disrupted following traumatic stressors. Additionally, traumatic or chronic stressors that occur during adulthood or early life can cause long-lasting disturbances in the eCB system. These alterations interfere with hypothalamic-pituitary-adrenal axis function and may be involved in lifelong increased fear and anxiety behaviors as well as increased risk for development of post-traumatic stress disorder (PTSD). Methods: This review focuses on the implications of trauma and significant stressors on eCB functionality and neural pathways, both in adolescence and into adulthood, as well as the current state of testing for CBD efficacy in treating pediatric and adult patients suffering from stress-induced eCB dysregulation. Articles were searched via Pubmed and included studies examining eCB modulation of stress-related disorders in both clinical settings and preclinical models. Conclusion: Given the potential for lifelong alterations in eCB signaling that can mediate stress responsiveness, consideration of pharmaceutical or nutraceutical agents that impact eCB targets may improve clinical outcomes in stress-related disorders. However, caution may be warranted in utilization of medicinal cannabinoid products that contain delta-9-tetrahydrocannabinol due to pronounced euphorigenic effects and potential to exacerbate stress-related behaviors. Other cannabinoid products, such as cannabidiol (CBD), have shown promise in reducing stress-related behaviors in pre-clinical models. Overall, pre-clinical evidence supports CBD as a potential treatment for stress or anxiety disorders resulting from previously stressful events, particularly by reducing fearful behavior and promoting extinction of contextual fear memories, which are hallmarks of PTSD. However, very limited clinical research has been conducted examining the potential effectiveness of CBD in this regard and should be examined further.

Regulation of DNA Methylation by Cannabidiol and Its Implications for Psychiatry: New Insights from In Vivo and In Silico Models

Cannabidiol (CBD) is a non-psychotomimetic compound present in cannabis sativa. Many recent studies have indicated that CBD has a promising therapeutic profile for stress-related psychiatric disorders, such as anxiety, schizophrenia and depression. Such a diverse profile has been associated with its complex pharmacology, since CBD can target different neurotransmitter receptors, enzymes, transporters and ion channels. However, the precise contribution of each of those mechanisms for CBD effects is still not yet completely understood. Considering that epigenetic changes make the bridge between gene expression and environment interactions, we review and discuss herein how CBD affects one of the main epigenetic mechanisms associated with the development of stress-related psychiatric disorders: DNA methylation (DNAm). Evidence from in vivo and in silico studies indicate that CBD can regulate the activity of the enzymes responsible for DNAm, due to directly binding to the enzymes and/or by indirectly regulating their activities as a consequence of neurotransmitter-mediated signaling. The implications of this new potential pharmacological target for CBD are discussed in light of its therapeutic and neurodevelopmental effects.

Targeting the cannabinoid system to counteract the deleterious effects of stress in Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative disorder characterized histologically in postmortem human brains by the presence of dense protein accumulations known as amyloid plaques and tau tangles. Plaques and tangles develop over decades of aberrant protein processing, post-translational modification, and misfolding throughout an individual’s lifetime. We present a foundation of evidence from the literature that suggests chronic stress is associated with increased disease severity in Alzheimer’s patient populations. Taken together with preclinical evidence that chronic stress signaling can precipitate cellular distress, we argue that chronic psychological stress renders select circuits more vulnerable to amyloid- and tau- related abnormalities. We discuss the ongoing investigation of systemic and cellular processes that maintain the integrity of protein homeostasis in health and in degenerative conditions such as Alzheimer’s disease that have revealed multiple potential therapeutic avenues. For example, the endogenous cannabinoid system traverses the central and peripheral neural systems while simultaneously exerting anti-inflammatory influence over the immune response in the brain and throughout the body. Moreover, the cannabinoid system converges on several stress-integrative neuronal circuits and critical regions of the hypothalamic-pituitary-adrenal axis, with the capacity to dampen responses to psychological and cellular stress. Targeting the cannabinoid system by influencing endogenous processes or exogenously stimulating cannabinoid receptors with natural or synthetic cannabis compounds has been identified as a promising route for Alzheimer’s Disease intervention. We build on our foundational framework focusing on the significance of chronic psychological and cellular stress on the development of Alzheimer’s neuropathology by integrating literature on cannabinoid function and dysfunction within Alzheimer’s Disease and conclude with remarks on optimal strategies for treatment potential.

Effect of long-term cannabidiol on learning and anxiety in a female Alzheimer’s disease mouse model

Cannabidiol is a promising potential therapeutic for neurodegenerative diseases, including Alzheimer’s disease (AD). Our laboratory has shown that oral CBD treatment prevents cognitive impairment in a male genetic mouse model of AD, the amyloid precursor protein 1 x presenilin 1 hemizygous (APPxPS1) mouse. However, as sex differences are evident in clinical populations and in AD mouse models, we tested the preventive potential of CBD therapy in female APPxPS1 mice. In this study, 2.5-month-old female wildtype-like (WT) and APPxPS1 mice were fed 20 mg/kg CBD or a vehicle via gel pellets daily for 8 months and tested at 10.5 months in behavioural paradigms relevant to cognition (fear conditioning, FC; cheeseboard, CB; and novel object recognition test, NORT) and anxiety-like behaviours (elevated plus maze, EPM). In the CB, CBD reduced latencies to find a food reward in APPxPS1 mice, compared to vehicle-treated APPxPS1 controls, and this treatment effect was not evident in WT mice. In addition, CBD also increased speed early in the acquisition of the CB task in APPxPS1 mice. In the EPM, CBD increased locomotion in APPxPS1 mice but not in WT mice, with no effects of CBD on anxiety-like behaviour. CBD had limited effects on the expression of fear memory. These results indicate preventive CBD treatment can have a moderate spatial learning-enhancing effect in a female amyloid-β-based AD mouse model. This suggests CBD may have some preventive therapeutic potential in female familial AD patients.

Cannabidiol for the treatment of autism spectrum disorder: hope or hype?

RATIONALE

Autism spectrum disorder (ASD) is defined as a group of neurodevelopmental disorders whose symptoms include impaired communication and social interaction, restricted and repetitive patterns of behavior, and varying levels of intellectual disability. ASD is observed in early childhood and is one of the most severe chronic childhood disorders in prevalence, morbidity, and impact on society. It is usually accompanied by attention deficit hyperactivity disorder, anxiety, depression, sleep disorders, and epilepsy. The treatment of ASD has low efficacy, possibly because it has a heterogeneous nature, and its neurobiological basis is not clearly understood. Drugs such as risperidone and aripiprazole are the only two drugs available that are recognized by the Food and Drug Administration, primarily for treating the behavioral symptoms of this disorder. These drugs have limited efficacy and a high potential for inducing undesirable effects, compromising treatment adherence. Therefore, there is great interest in exploring the endocannabinoid system, which modulates the activity of other neurotransmitters, has actions in social behavior and seems to be altered in patients with ASD. Thus, cannabidiol (CBD) emerges as a possible strategy for treating ASD symptoms since it has relevant pharmacological actions on the endocannabinoid system and shows promising results in studies related to disorders in the central nervous system.

OBJECTIVES

Review the preclinical and clinical data supporting CBD's potential as a treatment for the symptoms and comorbidities associated with ASD, as well as discuss and provide information with the purpose of not trivializing the use of this drug.

Controversial Link between Cannabis and Anticancer Treatments-Where Are We and Where Are We Going? A Systematic Review of the Literature

Simple Summary

In the field of oncology, preclinical research has shown that cannabis and cannabinoids modulate signaling pathways involved in cell proliferation, migration, invasion, angiogenesis, programmed cell death, and metastasis. Based on these findings, as medical cannabis becomes legal in more and more countries, cancer patients and their families are increasingly interested in the potential benefits of herbal medicine as an element of complementary and alternative medicine in their treatment. Although its clinical efficacy has been demonstrated in preclinical studies, clinical trials with cancer patients are lacking. To draw clear conclusions, we await the results of further prospective and randomized studies on this clinically relevant topic.

Abstract

Background and Objectives: Cannabinoids are currently used in cancer patients primarily for their pain-relieving and antiemetic properties. The aim of our review was to synthesize all available data of studies evaluating the therapeutic efficacy of cannabis in combination with oncological treatments in cancer patients and to explore ongoing studies with different goals and medical areas registered in the field of oncology worldwide. Materials and Methods: This study was performed in accordance with the PRISMA guidelines. A search using MEDLINE/PubMed database was performed between 1 January 2006 and 1 March 2022. Search terms included the following: cannabidiol, cannabis, CBD, dronabinol, endocannabinoids, medical marijuana, nabiximols, nabilone, THC, and cancer. All studies that examined the efficacy of cannabis administered during oncological treatments, regardless of cancer localization, subtype, and sample size, were considered eligible. Results: In three studies, cannabis was administered to patients with glioblastoma, and in two other studies, cannabis was used in combination with immunotherapy in various cancer subgroups. The results of the clinical trials in cancer patients are not sufficient to draw conclusions at this time. Interestingly, several other studies addressing the systemic effects of cannabinoids in cancer patients are currently listed in the U.S. National Library of Medicine’s registry on the ClinicalTrials.gov website. However, only one of the registered studies examined the efficacy of cannabinoids as a potential option for systemic cancer treatment. Conclusions: Although cannabis is touted to the public as a cancer cure, clinical trials need to clarify which combinations of chemotherapeutic agents with cannabinoids are useful for cancer patients.

Tetrahydrocannabinol and cannabidiol medicines for chronic pain and mental health conditions

Combination tetrahydrocannabinol (THC)/cannabidiol (CBD) medicines or CBD-only medicines are prospective treatments for chronic pain, stress, anxiety, depression, and insomnia. THC and CBD increase signaling from cannabinoid receptors, which reduces synaptic transmission in parts of the central and peripheral nervous systems and reduces the secretion of inflammatory factors from immune and glial cells. The overall effect of adding CBD to THC medicines is to enhance the analgesic effect but counteract some of the adverse effects. There is substantial evidence for the effectiveness of THC/CBD combination medicines for chronic pain, especially neuropathic and nociplastic pain or pain with an inflammatory component. For CBD-only medication, there is substantial evidence for stress, moderate evidence for anxiety and insomnia, and minimal evidence for depression and pain. THC/CBD combination medicines have a good tolerability and safety profile relative to opioid analgesics and have negligible dependence and abuse potential; however, should be avoided in patients predisposed to depression, psychosis and suicide as these conditions appear to be exacerbated. Non-serious adverse events are usually dose-proportional, subject to tachyphylaxis and are rarely dose limiting when patients are commenced on a low dose with gradual up-titration. THC and CBD inhibit several Phase I and II metabolism enzymes, which increases the exposure to a wide range of drugs and appropriate care needs to be taken. Low-dose CBD that appears effective for chronic pain and mental health has good tolerability and safety, with few adverse effects and is appropriate as an initial treatment.

Dose-Dependent Antidepressant-Like Effects of Cannabidiol in Aged Rats

Aging predisposes to late-life depression and since antidepressants are known to change their efficacy with age, novel treatment options are needed for our increased aged population. In this context, the goal of the present study was to evaluate the potential antidepressant-like effect of cannabidiol in aged rats. For this purpose, 19–21-month-old Sprague–Dawley rats were treated for 7 days with cannabidiol (dose range: 3–30 mg/kg) and scored under the stress of the forced-swim test. Hippocampal cannabinoid receptors and cell proliferation were evaluated as potential molecular markers underlying cannabidiol’s actions. The main results of the present study demonstrated that cannabidiol exerted a dose-dependent antidepressant-like effect in aged rats (U-shaped, effective at the intermediate dose of 10 mg/kg as compared to the other doses tested), without affecting body weight. None of the molecular markers analyzed in the hippocampus were altered by cannabidiol’s treatment. Overall, this study demonstrated a dose-dependent antidepressant-like response for cannabidiol at this age-window (aged rats up to 21 months old) and in line with other studies suggesting a beneficial role for this drug in age-related behavioral deficits.

The antidepressant and anxiolytic effects of cannabinoids in chronic unpredictable stress: a preclinical systematic review and meta-analysis

Neuroscience research presents contradictory evidence in support of both the protective and destructive effects of cannabinoids in depression. Therefore, this systematic review and meta-analysis summarizes the existing preclinical literature on the effects of cannabinoid administration in the chronic unpredictable stress model of depression in order to evaluate the effects of cannabinoids and identify gaps in the literature. After protocol registration (PROSPERO #CRD42020219986), we systematically searched Scopus, Embase, Psychology & Behavioral Sciences Collection, APA PsychINFO, PubMed, CINAHL Complete, and ProQuest Dissertations & Theses Global from the earliest record of the databases, February 1964, to November 2020 for articles that met inclusion criteria (e.g., rodent subjects and administration of a cannabinoid. A total of 26 articles were included representing a sample size estimate of 1132 rodents with the majority of articles administering daily intraperitoneal injections during chronic unpredictable stress. These articles were evaluated using a modified SYRCLE's risk-of-bias tool. For each continuous behavioral measure, the standardized mean difference was calculated between cannabinoid and vehicle groups in rodents subjected to chronic unpredictable stress. The effects of cannabinoids on depressive-like behavior was evaluated using a multilevel mixed-effects model with effect size weights nested within control groups. Cannabinoid administration moderately improved the pooled negative effects of chronic unpredictable stress on anhedonia, learned helplessness, novelty suppressed feeding, time in the anxiogenic context, and entries into the anxiogenic context. Although the interpretations are limited, these findings suggest that with further investigation, cannabinoids may be a viable long-term treatment for stress-related psychopathologies such as depression.

Modulation of Endocannabinoid System Components in Depression: Pre-Clinical and Clinical Evidence

Depression is characterized by continuous low mood and loss of interest or pleasure in enjoyable activities. First-line medications for mood disorders mostly target the monoaminergic system; however, many patients do not find relief with these medications, and those who do suffer from negative side effects and a discouragingly low rate of remission. Studies suggest that the endocannabinoid system (ECS) may be involved in the etiology of depression and that targeting the ECS has the potential to alleviate depression. ECS components (such as receptors, endocannabinoid ligands, and degrading enzymes) are key neuromodulators in motivation and cognition as well as in the regulation of stress and emotions. Studies in depressed patients and in animal models for depression have reported deficits in ECS components, which is motivating researchers to identify potential diagnostic and therapeutic biomarkers within the ECS. By understanding the effects of cannabinoids on ECS components in depression, we enhance our understanding of which brain targets they hit, what biological processes they alter, and eventually how to use this information to design better therapeutic options. In this article, we discuss the literature on the effects of cannabinoids on ECS components of specific depression-like behaviors and phenotypes in rodents and then describe the findings in depressed patients. A better understanding of the effects of cannabinoids on ECS components in depression may direct future research efforts to enhance diagnosis and treatment.

Early-life stress induces emotional and molecular alterations in female mice that are partially reversed by cannabidiol

Gender is considered as a pivotal determinant of mental health. Indeed, several psychiatric disorders such as anxiety and depression are more common and persistent in women than in men. In the past two decades, impaired brain energy metabolism has been highlighted as a risk factor for the development of these psychiatric disorders. However, comprehensive behavioural and neurobiological studies in brain regions relevant to anxiety and depression symptomatology are scarce. In the present study, we summarize findings describing cannabidiol effects on anxiety and depression in maternally separated female mice as a well-established rodent model of early-life stress associated with many mental disorders. Our results indicate that cannabidiol could prevent anxiolytic- and depressive-related behaviour in early-life stressed female mice. Additionally, maternal separation with early weaning (MSEW) caused long-term changes in brain oxidative metabolism in both nucleus accumbens and amygdalar complex measured by cytochrome c oxidase quantitative histochemistry. However, cannabidiol treatment could not revert brain oxidative metabolism impairment. Moreover, we identified hyperphosphorylation of mTOR and ERK 1/2 proteins in the amygdala but not in the striatum, that could also reflect altered brain intracellular signalling related with to bioenergetic impairment. Altogether, our study supports the hypothesis that MSEW induces profound long-lasting molecular changes in mTOR signalling and brain energy metabolism related to depressive-like and anxiety-like behaviours in female mice, which were partially ameliorated by CBD administration.

Cannabinoid CB1 Receptor Involvement in the Actions of CBD on Anxiety and Coping Behaviors in Mice

The anxiolytic and antidepressant properties of cannabidiol (CBD) have been evaluated in several studies. However, the molecular mechanisms involved in these actions remain unclear. A total of 130 male mice were used. CBD’s ability to modulate emotional disturbances (anxiety and depressive-like behaviors) was evaluated at different doses in wild-type (CD1; 10, 20 and 30 mg/kg; i.p.) and knockout (CB1KO, CB2KO; GPR55KO; 20 mg/kg) mice. Moreover, CBD effects (20 mg/kg; i.p.) were evaluated in mice previously treated with the CB1r-antagonist SR141716A (2mg/kg; i.p.). Relative gene expression analyses of Cnr1 and Cnr2, Gpr55 and GABA(A)α2 and γ2 receptor subunits were performed in the amygdala (AMY) and hippocampus (HIPP) of CD1 mice. CBD (10 and 20 mg/kg) showed anxiolytic and antidepressant actions in CD1 mice, being more effective at 20 mg/kg. Its administration did not induce anxiolytic actions in CB1KO mice, contrary to CB2KO and GPR55KO. In all of them, the lack of cannabinoid receptors did not modify the antidepressant activity of CBD. Interestingly, the administration of the CB1r antagonist SR141716A blocked the anxiolytic-like activity of CBD. Real-time PCR studies revealed a significant reduction in Cnr1 and GABA(A)α2 and γ2 gene expression in the HIPP and AMY of CD1 mice treated with CBD. Opposite changes were observed in the Cnr2. Indeed, Gpr55 was increased in the AMY and reduced in the HIPP. CB1r appears to play a relevant role in modulating the anxiolytic actions of CBD. Moreover, this study revealed that CBD also modified the gene expression of GABA(A) subunits α2 and γ2 and CB1r, CB2r and GPR55, in a dose- and brain-region-dependent manner, supporting a multimodal mechanism of action for CBD.

Geotemporospatial and causal inferential epidemiological overview and survey of USA cannabis, cannabidiol and cannabinoid genotoxicity expressed in cancer incidence 2003-2017: part 1 - continuous bivariate analysis

BACKGROUND

The genotoxic and cancerogenic impacts of population-wide cannabinoid exposure remains an open but highly salient question. The present report examines these issues from a continuous bivariate perspective with subsequent reports continuing categorical and detailed analyses.

METHODS

Age-standardized state census incidence of 28 cancer types (including "All (non-skin) Cancer") was sourced using SEER*Stat software from Centres for Disease Control and National Cancer Institute across US states 2001-2017. It was joined with drug exposure data from the nationally representative National Survey of Drug Use and Health conducted annually by the Substance Abuse and Mental Health Services Administration 2003-2017, response rate 74.1%. Cannabinoid data was from Federal seizure data. Income and ethnicity data sourced from the US Census Bureau. Data was processed in R.

RESULTS

Nineteen thousand eight hundred seventy-seven age-standardized cancer rates were returned. Based on these rates and state populations this equated to 51,623,922 cancer cases over an aggregated population 2003-2017 of 124,896,418,350. Regression lines were charted for cancer-substance exposures for cigarettes, alcohol use disorder (AUD), cannabis, THC, cannabidiol, cannabichromene, cannabinol and cannabigerol. In this substance series positive trends were found for 14, 9, 6, 9, 12, 6, 9 and 7 cancers; with largest minimum E-Values (mEV) of 1.76 × 109, 4.67 × 108, 2.74 × 104, 4.72, 2.34 × 1018, 2.74 × 1017, 1.90 × 107, 5.05 × 109; and total sum of exponents of mEV of 34, 32, 13, 0, 103, 58, 25, 31 indicating that cannabidiol followed by cannabichromene are the most strongly implicated in environmental carcinogenesis. Breast cancer was associated with tobacco and all cannabinoids (from mEV = 3.53 × 109); "All Cancer" (non-skin) linked with cannabidiol (mEV = 1.43 × 1011); pediatric AML linked with cannabis (mEV = 19.61); testicular cancer linked with THC (mEV = 1.33). Cancers demonstrating elevated mEV in association with THC were: thyroid, liver, pancreas, AML, breast, oropharynx, CML, testis and kidney. Cancers demonstrating elevated mEV in relation to cannabidiol: prostate, bladder, ovary, all cancers, colorectum, Hodgkins, brain, Non-Hodgkins lymphoma, esophagus, breast and stomach.

CONCLUSION

Data suggest that cannabinoids including THC and cannabidiol are important community carcinogens exceeding the effects of tobacco or alcohol. Testicular, (prostatic) and ovarian tumours indicate mutagenic corruption of the germline in both sexes; pediatric tumourigenesis confirms transgenerational oncogenesis; quantitative criteria implying causality are fulfilled.

CB1 receptor antagonist AM4113 reverts the effects of cannabidiol on cue and stress-induced reinstatement of cocaine-seeking behaviour in mice

No pharmacological treatments are yet approved for patients with cocaine use disorders. Cannabidiol, a constituent of the C. sativa plant has shown promising results in rodent models of drug addiction. However, the specific effects and mechanisms of action of cannabidiol in rodent operant models of extinction-based abstinence and drug-seeking relapse remain unclear. Cannabidiol (10 and 20 mg/kg, i.p.) was injected during extinction training to male CD-1 mice previously trained to self-administer cocaine (0.75 mg/kg/infusion). Then, we evaluated the reinstatement of cocaine seeking induced by cues and stressful stimuli (footshock). We found that cannabidiol (10 and 20 mg/kg) did not modulate extinction learning. After cannabidiol 20 mg/kg treatment, increased levels of CB1 receptor protein were found in the prelimbic and orbitofrontal regions of the prefrontal cortex, and in the ventral striatum; an effect paralleled by a reduction of striatal ∆FosB accumulation and an increment of GluR2 AMPA receptor subunits. Furthermore, cue-induced reinstatement of cocaine seeking was attenuated by cannabidiol. Unexpectedly, cannabidiol 20 mg/kg facilitated stress-induced restoration of cocaine-seeking behaviour. To ascertain the participation of CB1 receptors in these behavioural changes, we administered the CB1 antagonist AM4113 (5 mg/kg) before each reinstatement session. Both, the attenuation of cue-induced reinstatement and the facilitation of stress-induced reestablishment were abolished by AM4113 in cannabidiol 20 mg/kg-treated mice. Our results reveal a series of complex CB1-related changes induced by cannabidiol with a varying impact on the reinstatement of cocaine-seeking behaviour that could limit its therapeutic applications.

Geospatiotemporal and causal inference study of cannabis and other drugs as risk factors for female breast cancer USA 2003-2017

Breast cancer (BC) is the commonest human cancer and its incidence (BC incidence, BCI) is rising worldwide. Whilst both tobacco and alcohol have been linked to BCI genotoxic cannabinoids have not been investigated. Age-adjusted state-based BCI 2003-2017 was taken from the Surveillance Epidemiology and End Results database of the Centers for Disease Control. Drug use from the National Survey of Drug Use and Health, response rate 74.1%. Median age, median household income and ethnicity were from US census. Inverse probability weighted (ipw) multivariable regression conducted in R. In bivariate analysis BCI was shown to be significantly linked with rising cannabis exposure {β-est. = 3.93 [95% confidence interval 2.99, 4.87], P = 1.10 × 10-15}. At 8 years lag cigarettes:cannabis [β-est. = 2660 (2150.4, 3169.3), P = 4.60 × 10-22] and cannabis:alcoholism [β-est. = 7010 (5461.6, 8558.4), P = 1.80 × 10-17] were significant in ipw-panel regression. Terms including cannabidiol [CBD; β-est. = 16.16 (0.39, 31.93), P = 0.446] and cannabigerol [CBG; β-est. = 6.23 (2.06, 10.39), P = 0.0034] were significant in spatiotemporal models lagged 1:2 years, respectively. Cannabis-liberal paradigms had higher BCI [67.50 ± 0.26 v. 65.19 ± 0.21/100 000 (mean ± SEM), P = 1.87 × 10-11; β-est. = 2.31 (1.65, 2.96), P = 9.09 × 10-12]. 55/58 expected values >1.25 and 13/58 >100. Abortion was independently and causally significant in space-time models. Data show that exposure to cannabis and the cannabinoids Δ9-tetrahydrocannabinol, CBD, CBG and alcoholism fulfil quantitative causal criteria for BCI across space and time. Findings are robust to adjustment for age and several known sociodemographic, socio-economic and hormonal risk factors and establish cannabinoids as an additional risk factor class for breast carcinogenesis. BCI is higher under cannabis-liberal legal paradigms.