If you struggle with chronic stress or anxiety, you may be considering using CBD oil or CBD vape pens. There is already good evidence of CBD’s usefulness for treating generalized anxiety disorder, panic disorder, social anxiety disorder, obsessive–compulsive disorder (OCD), post-traumatic stress disorder (PTSD). Cannabidiol as a Potential Treatment for Anxiety Disorders Cannabidiol (CBD), a Cannabis sativa constituent, is a pharmacologically broad-spectrum drug that in recent years has drawn increasing
CBD for Stress & Anxiety
We all know what it feels like to “stress out” before an exam or important event. But sometimes a challenging job, family demands, or just surviving the unexpected events of life can feel like a continual test. If that impending sense of disaster is never-ending it’s a sign of chronic anxiety, and you might need an intervention to reset your baseline stress-response.
Unfortunately, the medical system’s solution to anxiety falls short for many people. If you struggle with chronic stress or anxiety, you may be considering supplementing your treatment with CBD oil, CBD vape pens, or CBD gummies. But what’s the evidence that CBD works?
The growing popularity of CBD products as anti-anxiety supplements is backed with plenty of convincing research, though there’s still a long way to go. Several clinical trials with humans are currently underway, but there is already good evidence of CBD’s usefulness for:
- Generalized anxiety disorder
- Panic disorder
- Social anxiety disorder
- Obsessive–compulsive disorder (OCD)
- Post-traumatic stress disorder (PTSD)
To understand how CBD works, let’s dive into the science of how stress affect your body & brain. (If you’re already up on this topic, feel free to skip ahead to the CBD sections. )
Anxiety: How It Becomes Chronic
One in four Americans will suffer from an anxiety disorder during their lifetime — where feelings of dread, unpreparedness, and imminent danger recur more and more often, leading to racing thoughts and physical reactions. Where do these feelings come from?
A major contributor is our genetics. Small differences in our hormones or neurotransmitters (like serotonin and norepinephrine) can massively impact how we respond to stress. Another piece of the puzzle includes environmental & lifestyle toxins that affect our neurochemistry.
But probably the biggest source of anxiety is stress. Chronic stress trains your brain to feel anxious — it wants you to “remember” so you can anticipate (and hopefully avoid) more stress in the future.
If we were still running free in nature — avoiding bears and quicksand — this stress response would be useful. But we’re required to walk into stressful situations over and over and over again — and each time we have to bring our best selves without “remembering” that we’d be better off running away to a tropical beach.
Chronic Stress & Anxiety Damage Your Body
Small bursts of stress hormones tell your body to prepare for a “fight or flight” situation. Unfortunately, our bodies weren’t designed to handle a perpetual state of panic. Chronically high levels of stress hormones — particularly cortisol — wreak havoc everywhere, with consequences that include:
- Heart disease
- Digestive problems
- Weakened immune system
- Weight gain
- Muscular tension
The good news? If you’re constantly stressed and also suffer from any of these problems, treatment could help your symptoms improve.
Stress Messes with Your Brain Chemistry
In addition to damaging your body, chronic stress also rewires your brain. Stress hormones tell the brain to: “Focus, feel less and get ready.” Unfortunately, when this message is never turned off, your brain will make changes to tune out the message.
Scientists are still discovering the many layers of changes that take place in response to chronic stress — but they include both the brain’s structure and chemistry . Certain regions of the brain become hyperactive, while others atrophy and even shrink, and levels of neurotransmitters (like serotonin, dopamine and endocannabinoids ) and their receptors also change.
Even if you manage to de-stress your life, these changes could persist — along with their negative impacts on the rest of your body. When this happens, you may need support restoring balance to your brain.
Weed’s Secret Anti-Anxiety Ingredient
If you’ve experimented with cannabis products, you’re probably familiar with the spectrum of reactions people can have when they get “high.” In movies where a character smokes weed, one of two scenarios plays out — either they sit back, relax and enjoy themselves. or they turn into a paranoid, twitchy mess.
It turns out that this unpredictability comes mainly from variations in the quantities and ratios of phytocannabinoids and synergistic terpenes. Too much THC can overstimulate the body’s CB1 receptors, while THC’s non-intoxicating sister molecule, cannabidiol (CBD), can directly and indirectly counteract the anxiety people experience from too much THC . Different cannabis strains have different concentrations of these two molecules — which is one reason for vastly different anxiety responses.
Thanks in part to medical marijuana and legalization efforts, humanity is experiencing a renaissance in cannabis research and production techniques — making it much easier to produce whole-plant CBD without any THC, creating products with the healing properties of cannabis without the cultural stigma or unpleasant side-effects traditionally associated with cannabis.
Evidence that CBD Soothes Stress & Anxiety
Beyond the glowing testimonials of individuals who successfully treat their anxiety with CBD oil, there is also a growing body of scientific evidence that CBD works. Most research has been done in rodents. A recent review discusses 32 different rodent studies that tested CBD’s effects on anxiety — and only one didn’t see useful results.
Human experiments are costly and legally complicated — which makes it no surprise that human studies are fewer and less conclusive. But overall, two exciting uses for CBD in anxiety have emerged for both rodents and humans:
- Less anxiety in response to stress. These experiments put test subjects in a stressful situation and measure their anxiety levels:
- Rodent evidence: In one example, mice were placed in a cage with a boa constrictor. Mice given low doses of CBD (equivalent to a 20 mg dosage for a 150-pound person) spent more time scanning their environment and choosing the most strategic location to run instead of panicking.
- Human evidence: Public speaking is the human equivalent of a boa constrictor. CBD improves performance anxiety both for people without anxiety disorders and also for people with social anxiety disorder .
- Extinction learning: One way we get over anxiety is through “extinction learning,” or learning to let go of triggers when there’s nothing left to fear. These experiments often train test subjects to associate something harmless with something painful, and then measure how long it takes to stop fearing the harmless trigger after they stop delivering pain. This is particularly relevant for people suffering from PTSD:
- Rodent evidence: Rodents freeze in fear when they are conditioned to expect an electric shock. However, if scientists give them CBD during the extinction learning process , they are less likely to freeze up in expectation — even after the CBD has worn off .
- Human evidence: People have also been conditioned to expect an electric shock when they see a visual cue. Those who inhaled a 32 mg dosage of CBD during extinction training (without shocks) were less expectant of receiving a shock when tested two days later — long after the CBD had worn off.
How CBD Combats Anxiety
Cannabidiol has more than 65 targets throughout the body , which makes it difficult to pinpoint the sources of its many different therapeutic properties. Studies currently suggest that CBD counters anxiety by stimulating neurotransmitter systems and neural regeneration. Here’s the evidence:
- Serotonin: Most people associate serotonin with happiness. H owever, the role of this neurotransmitter is very complex, and its effects depend on where it is and what it binds to. (Contrary to popular belief, more serotonin is not necessarily better — dysfunction can stem from low or high levels of serotonin, as well as from malfunctions with their receptors.) Serotonin has at least 14 different receptors, but CBD specifically binds to 5-HT 1A which is thought to have the strongest role in anxiety disorders . The anti-anxiety drug buspirone also binds to this particular receptor, which explains the anti-anxiety effects of CBD on rats exposed to stressful situations.
- Endocannabinoids : Your body naturally produces cannabinoids, which are used throughout your body and brain in the endocannabinoid system . This system can become dysregulated under chronic stress . However, CBD could help restore balance to the endocannabinoid system by preventing overstimulation of your CB1 receptors and by boosting your body’s production of endocannabinoids. Rodent experiments show that CBD relieves OCD and other anxious behaviours by acting on the endocannabinoid system, which is involved in processing and forgetting our fears — vital for extinction learning.
- Neural regeneration: Although chronic stress can damage neurons and even shrink brains , certain areas of the brain are still capable of regeneration. Throughout our lives we continue to form new neurons, make new connections, and grow our brains — and CBD apparently boosts this process. This means that CBD could help to counterbalance the brain damage caused by chronic stress. Numerous studies have proved that CBD encourages neural regeneration , particularly in the hippocampus. In fact, its ability to reduce anxiety in chronically-stressed mice comes from CBD’s power to stimulate the growth of new neurons . ( For more on CBD’s role in neuroplasticity and neural regeneration, see our upcoming article on depression .)
Integrative Treatments for Stress & Anxiety
With so many constant sources of stress, people often need a more holistic approach to heal from anxiety. Even medical doctors have begun suggesting that people combine traditional psychotherapy & pharmaceutical treatments with relaxation techniques like yoga & meditation.
If chronic stress and anxiety have rewired your brain, it will take work & time to undo the damage. Eventually, you can change your habitual mind patterns, but you might get there even faster if you actively help your brain neurons grow and rebuild. (For more on this topic, see our upcoming article on natural ways to increase neural regeneration .)
If you choose to supplement with CBD, it will work best as part of a comprehensive anxiety treatment plan. We encourage you to speak first with a trusted medical professional about your plans, especially if you currently take prescription medications . Similar to grapefruits, CBD could interfere with your body’s ability to metabolize drugs . A doctor or integrative practitioner can also help you rule out any contributing deficiencies and other worrisome health issues.
We wish you success on your journey and deep healing for your brain and your body.
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Cannabidiol as a Potential Treatment for Anxiety Disorders
Cannabidiol (CBD), a Cannabis sativa constituent, is a pharmacologically broad-spectrum drug that in recent years has drawn increasing interest as a treatment for a range of neuropsychiatric disorders. The purpose of the current review is to determine CBD’s potential as a treatment for anxiety-related disorders, by assessing evidence from preclinical, human experimental, clinical, and epidemiological studies. We found that existing preclinical evidence strongly supports CBD as a treatment for generalized anxiety disorder, panic disorder, social anxiety disorder, obsessive–compulsive disorder, and post-traumatic stress disorder when administered acutely; however, few studies have investigated chronic CBD dosing. Likewise, evidence from human studies supports an anxiolytic role of CBD, but is currently limited to acute dosing, also with few studies in clinical populations. Overall, current evidence indicates CBD has considerable potential as a treatment for multiple anxiety disorders, with need for further study of chronic and therapeutic effects in relevant clinical populations.
Electronic supplementary material
The online version of this article (doi:10.1007/s13311-015-0387-1) contains supplementary material, which is available to authorized users.
Keywords: Cannabidiol, Endocannabinoids, Anxiety, Generalized anxiety disorder, Post-traumatic stress disorder
Fear and anxiety are adaptive responses essential to coping with threats to survival. Yet excessive or persistent fear may be maladaptive, leading to disability. Symptoms arising from excessive fear and anxiety occur in a number of neuropsychiatric disorders, including generalized anxiety disorder (GAD), panic disorder (PD), post-traumatic stress disorder (PTSD), social anxiety disorder (SAD), and obsessive–compulsive disorder (OCD). Notably, PTSD and OCD are no longer classified as anxiety disorders in the recent revision of the Diagnostic and Statistical Manual of Mental Disorders-5; however, excessive anxiety is central to the symptomatology of both disorders. These anxiety-related disorders are associated with a diminished sense of well-being, elevated rates of unemployment and relationship breakdown, and elevated suicide risk [1–3]. Together, they have a lifetime prevalence in the USA of 29 % , the highest of any mental disorder, and constitute an immense social and economic burden [5, 6].
Currently available pharmacological treatments include serotonin reuptake inhibitors, serotonin–norepinephrine reuptake inhibitors, benzodiazepines, monoamine oxidase inhibitors, tricyclic antidepressant drugs, and partial 5-hydroxytryptamine (5-HT)1A receptor agonists. Anticonvulsants and atypical antipsychotics are also used to treat PTSD. These medications are associated with limited response rates and residual symptoms, particularly in PTSD, and adverse effects may also limit tolerability and adherence [7–10]. The substantial burden of anxiety-related disorders and the limitations of current treatments place a high priority on developing novel pharmaceutical treatments.
Cannabidiol (CBD) is a phytocannabinoid constituent of Cannabis sativa that lacks the psychoactive effects of ∆ 9- tetrahydrocannabinol (THC). CBD has broad therapeutic properties across a range of neuropsychiatric disorders, stemming from diverse central nervous system actions [11, 12]. In recent years, CBD has attracted increasing interest as a potential anxiolytic treatment [13–15]. The purpose of this review is to assess evidence from current preclinical, clinical, and epidemiological studies pertaining to the potential risks and benefits of CBD as a treatment for anxiety disorders.
A search of MEDLINE (PubMed), PsycINFO, Web of Science Scopus, and the Cochrane Library databases was conducted for English-language papers published up to 1 January 2015, using the search terms “cannabidiol” and “anxiety” or “fear” or “stress” or “anxiety disorder” or “generalized anxiety disorder” or “social anxiety disorder” or “social phobia” or “post-traumatic stress disorder” or “panic disorder” or “obsessive compulsive disorder”. In total, 49 primary preclinical, clinical, or epidemiological studies were included. Neuroimaging studies that documented results from anxiety-related tasks, or resting neural activity, were included. Epidemiological or clinical studies that assessed CBD’s effects on anxiety symptoms, or the potential protective effects of CBD on anxiety symptoms induced by cannabis use (where the CBD content of cannabis is inferred via a higher CBD:THC ratio), were included.
CBD Pharmacology Relevant to Anxiety
General Pharmacology and Therapeutic Profile
Cannabis sativa, a species of the Cannabis genus of flowering plants, is one of the most frequently used illicit recreational substances in Western culture. The 2 major phyto- cannabinoid constituents with central nervous system activity are THC, responsible for the euphoric and mind-altering effects, and CBD, which lacks these psychoactive effects. Preclinical and clinical studies show CBD possesses a wide range of therapeutic properties, including antipsychotic, analgesic, neuroprotective, anticonvulsant, antiemetic, antioxidant, anti-inflammatory, antiarthritic, and antineoplastic properties (see [11, 12, 16–19] for reviews). A review of potential side effects in humans found that CBD was well tolerated across a wide dose range, up to 1500 mg/day (orally), with no reported psychomotor slowing, negative mood effects, or vital sign abnormalities noted .
CBD has a broad pharmacological profile, including interactions with several receptors known to regulate fear and anxiety-related behaviors, specifically the cannabinoid type 1 receptor (CB1R), the serotonin 5-HT1A receptor, and the transient receptor potential (TRP) vanilloid type 1 (TRPV1) receptor [11, 12, 19, 21]. In addition, CBD may also regulate, directly or indirectly, the peroxisome proliferator-activated receptor-γ, the orphan G-protein-coupled receptor 55, the equilibrative nucleoside transporter, the adenosine transporter, additional TRP channels, and glycine receptors [11, 12, 19, 21]. In the current review of primary studies, the following receptor-specific actions were found to have been investigated as potential mediators of CBD’s anxiolytic action: CB1R, TRPV1 receptors, and 5-HT1A receptors. Pharmacology relevant to these actions is detailed below.
The Endocannabinoid System
Following cloning of the endogenous receptor for THC, namely the CB1R, endogenous CB1R ligands, or “endocannabinoids” (eCBs) were discovered, namely anandamide (AEA) and 2-arachidonoylglycerol (reviewed in ). The CB1R is an inhibitory Gi/o protein-coupled receptor that is mainly localized to nerve terminals, and is expressed on both γ-aminobutryic acid-ergic and glutamatergic neurons. eCBs are fatty acid derivatives that are synthesized on demand in response to neuronal depolarization and Ca 2+ influx, via cleavage of membrane phospholipids. The primary mechanism by which eCBs regulate synaptic function is retrograde signaling, wherein eCBs produced by depolarization of the postsynaptic neuron activate presynaptic CB1Rs, leading to inhibition of neurotransmitter release . The “eCB system” includes AEA and 2-arachidonoylglycerol; their respective degradative enzymes fatty acid amide hydroxylase (FAAH) and monoacylglycerol lipase; the CB1R and related CB2 receptor (the latter expressed mainly in the periphery); as well as several other receptors activated by eCBs, including the TRPV1 receptor, peroxisome proliferator-activated receptor-γ, and G protein-coupled 55 receptor, which functionally interact with CB1R signaling (reviewed in [21, 24]). Interactions with the TRPV1 receptor, in particular, appear to be critical in regulating the extent to which eCB release leads to inhibition or facilitation of presynaptic neurotransmitter release . The TRPV1 receptor is a postsynaptic cation channel that underlies sensation of noxious heat in the periphery, with capsacin (hot chili) as an exogenous ligand. TRPV1 receptors are also expressed in the brain, including the amygdala, periaqueductal grey, hippocampus, and other areas [26, 27].
The eCB system regulates diverse physiological functions, including caloric energy balance and immune function . The eCB system is also integral to regulation of emotional behavior, being essential to forms of synaptic plasticity that determine learning and response to emotionally salient, particularly highly aversive events [29, 30]. Activation of CB1Rs produces anxiolytic effects in various models of unconditioned fear, relevant to multiple anxiety disorder symptom domains (reviewed in [30–33]). Regarding conditioned fear, the effect of CB1R activation is complex: CB1R activation may enhance or reduce fear expression, depending on brain locus and the eCB ligand ; however, CB1R activation potently enhances fear extinction , and can prevent fear reconsolidation. Genetic manipulations that impede CB1R activation are anxiogenic , and individuals with eCB system gene polymorphisms that reduce eCB tone—for example, FAAH gene polymorphisms—exhibit physiological, psychological, and neuroimaging features consistent with impaired fear regulation . Reduction of AEA–CB1R signaling in the amygdala mediates the anxiogenic effects of corticotropin-releasing hormone , and CB1R activation is essential to negative feedback of the neuroendocrine stress response, and protects against the adverse effects of chronic stress [38, 39]. Finally, chronic stress impairs eCB signaling in the hippocampus and amygdala, leading to anxiety [40, 41], and people with PTSD show elevated CB1R availability and reduced peripheral AEA, suggestive of reduced eCB tone .
Accordingly, CB1R activation has been suggested as a target for anxiolytic drug development [15, 43, 44]. Proposed agents for enhancing CB1R activation include THC, which is a potent and direct agonist; synthetic CB1R agonists; FAAH inhibitors and other agents that increase eCB availability, as well as nonpsychoactive cannabis phytocannabinoids, including CBD. While CBD has low affinity for the CB1R, it functions as an indirect agonist, potentially via augmentation of CB1R constitutional activity, or via increasing AEA through FAAH inhibition (reviewed in ).
Several complexities of the eCB system may impact upon the potential of CBD and other CB1R-activating agents to serve as anxiolytic drugs. First, CB1R agonists, including THC and AEA, have a biphasic effect: low doses are anxiolytic, but higher doses are ineffective or anxiogenic, in both preclinical models in and humans (reviewed in [33, 45]). This biphasic profile may stem from the capacity of CB1R agonists to also activate TRPV1 receptors when administered at a high, but not low dose, as demonstrated for AEA . Activation of TRPV1 receptors is predominantly anxiogenic, and thus a critical balance of eCB levels, determining CB1 versus TRPV1 activation, is proposed to govern emotional behavior [27, 47]. CBD acts as a TRPV1 agonist at high concentrations, potentially by interfering with AEA inactivation . In addition to dose-dependent activation of TRPV1 channels, the anxiogenic versus anxiolytic balance of CB1R agonists also depends on dynamic factors, including environmental stressors [33, 49].
The 5-HT1A receptor (5-HT1AR) is an established anxiolytic target. Buspirone and other 5-HT1AR agonists are approved for the treatment of GAD, with fair response rates . In preclinical studies, 5-HT1AR agonists are anxiolytic in animal models of general anxiety , prevent the adverse effects of stress , and enhance fear extinction . Both pre- and postsynaptic 5-HT1ARs are coupled to various members of the Gi/o protein family. They are expressed on serotonergic neurons in the raphe, where they exert autoinhibitory function, and various other brain areas involved in fear and anxiety [54, 55]. Mechanisms underlying the anxiolytic effects of 5-HT1AR activation are complex, varying between both brain region, and pre- versus postsynaptic locus, and are not fully established . While in vitro studies suggest CBD acts as a direct 5-HT1AR agonist , in vivo studies are more consistent with CBD acting as an allosteric modulator, or facilitator of 5-HT1A signaling .
Generalized Anxiety Models
Relevant studies in animal models are summarized in chronological order in Table Table1. 1 . CBD has been studied in a wide range of animal models of general anxiety, including the elevated plus maze (EPM), the Vogel-conflict test (VCT), and the elevated T maze (ETM). See Table Table1 1 for the anxiolytic effect specific to each paradigm. Initial studies of CBD in these models showed conflicting results: high (100 mg/kg) doses were ineffective, while low (10 mg/kg) doses were anxiolytic [59, 60]. When tested over a wide range of doses in further studies, the anxiolytic effects of CBD presented a bell-shaped dose–response curve, with anxiolytic effects observed at moderate but not higher doses [61, 90]. All further studies of acute systemic CBD without prior stress showed anxiolytic effects or no effect [62, 65], the latter study involving intracerebroventricular rather than the intraperitoneal route. No anxiogenic effects of acute systemic CBD dosing in models of general anxiety have yet been reported. As yet, few studies have examined chronic dosing effects of CBD in models of generalized anxiety. Campos et al.  showed that in rat, CBD treatment for 21 days attenuated inhibitory avoidance acquisition . Long et al.  showed that, in mouse, CBD produced moderate anxiolytic effects in some paradigms, with no effects in others.
Study Animal Route Dose Model Effect Receptor Involvement Silveira Filho et al.  WR i.p. 100 mg/kg,
GSCT No effect NA Zuardi et al.  WR i.p. 10 mg/kg,
CER Anxiolytic NA Onaivi et al.  ICR mice i.p. 0.01, 0.10, 0.50, 1.00, 2.50, 5.00, 10.00, 50.00, 100.00 mg/kg, acute EPM Anxiolytic Effects ↓ by IP flumazenil, unchanged by naloxone Guimaraes et al.  WR i.p. 2.5, 5.0, 10.0 and 20.0 mg/kg, acute EPM Anxiolytic NA Moreira et al.  WR i.p. 2.5, 5.0 and 10.0 mg/kg, acute VCT Anxiolytic Effect unchanged by IP flumazenil Resstel et al.  WR i.p. 10 mg/kg, acute CFC Anxiolytic NA Campos et al.  WR dlPAG 15.0, 30.0, 60.0 nmol/0.2 μl, acute EPM Anxiolytic Both effects ↓ by intra-dlPAG WAY100635 but not intra-dlPAG AM251 VCT Anxiolytic Bitencourt et al.  WR i.c.v. 2.0 μg/μl
5 min before extinction, acute
Anxiolytic Extinction effect ↓ by SR141716A but not capsazepine EPM before and 24 h after CFC No effect before CFC
Anxiolytic following CFC
Campos et al.  WR dlPAG 30, 60 mg/kg, acute EPM Anxiolytic Intra-dlPAG capsazepine renders 60 mg/kg anxiolytic Resstel et al.  WR i.p. 1, 10 or 20 mg/kg, acute RS Anxiolytic,
All effects ↓ by systemic WAY100635 EPM 24 h
Anxiolytic Soares et al.  WR dlPAG 15, 30 or 60 nmol, acute ETM Anxiolytic
All effects ↓ by intra-dlPAG WAY100635 but not AM251 PAG E-stim Panicolytic Long et al.  C57BL/6 J mice i.p. 1, 5, 10, 50 mg/kg, chronic, daily/21 d EPM No effect NA L-DT 1 mg/kg
SI No effect OF 50 mg/kg anxiolytic Lemos et al.  WR i.p.
10 mg/kg IP, 30 nmol intra-PL and intra-IL, acute CFC IP and PL anxiolytic IL anxiogenic NA Casarotto et al.  C57BL/6 J mice i.p. 15, 30, and 60 mg/kg, acute, or subchronic, daily/7 d MBT Anticompulsive Effect ↓ by IP AM251 but not WAY100635 Gomes et al.  WR BNST 15, 30, and 60 nmol, acute EPM Anxiolytic Both effects ↓ by intra BNST WAY100635 VCT Anxiolytic Granjeiro et a l.  WR Intracisternal 15, 30, and 60 nmol, acute RS Anxiolytic, ↓Pressor ↓Tachycardia NA EPM 24 h after RS Anxiolytic Deiana et al.  SM i.p.
120 mg/kg, acute MBT Anticompulsive NA Uribe-Marino et al.  SM i.p. 0.3, 3.0, 30.0 mg/kg, acute PS Panicolytic NA Stern et al.  WR i.p. 3, 10, 30 mg/kg
immediately after retrieval, acute
Reconsolidation blockade Anxiolytic
1 and 7 d old fear memories disrupted
Effect ↓ by AM251 but not WAY100635 Campos et al.  WR i.p. 5 mg/kg, subchronic, daily/7 d EPM following PS Anxiolytic Effects ↓ by IP WAY100635 Hsiao et al.  WR CeA 1 μg/μl REM sleep time ↓ REM sleep suppression NA EPM Anxiolytic OF Anxiolytic Gomes et al.  WR BNST 15, 30, 60 nmol, acute CFC Anxiolytic Both effects ↓ by intra-BNST WAY100635 El Batsh et al.  LE-H R i.p. 10 mg/kg, chronic,
CFC Anxiogenic NA Campos et al.  C57BL/6 mice i.p. 30 mg/kg 2 h after CUS,
chronic daily/14 d
EPM Anxiolytic Both effects ↓ by AM251 NSF Anxiolytic Do Monte et al.  L-E HR IL 1 μg or 0.4 μg/0.2 μl 5 min before extinction daily/4 d Extinction of CFC Anxiolytic Effect ↓ by IP rimonabant Campos et al.  Rat i.p. 5 mg/kg, chronic, daily/21 d ETM Anxiolytic
Panicolytic effect ↓ by intra-dlPAG WAY100635 Almeida et al.  Rat i.p. 1, 5, 15 mg/kg, acute SI Anxiolytic NA Gomes et al.  WR BNST 30 and 60 nmol, acute RS Anxiogenic
Effect ↓ by WAY100635 Twardowschy et al.  SM i.p. 3 mg/kg, acute PS Panicolytic Effects ↓ by IP WAY100635 Focaga et al.  WR PL 15, 30, 60 nmol, acute EPM Anxiogenic All effects ↓ by intra PL WAY100635
Anxiolytic EPM effect post-RS ↓ by IP metyrapone
EPM after RS Anxiolytic CFC Anxiolytic Nardo et al.  SM i.p. 30 mg/kg, acute MBT Anticompulsive NA da Silva et al.  WR SNpr 5 μg/0.2 μl GABAA blockade in dlSC Panicolytic Both effects ↓ by AM251
Effective doses are in bold
Receptor specific agents: AM251 = cannabinoid receptor type 1 (CB1R) inverse agonist; WAY100635 = 5-hydroxytryptamine 1A antagonist; SR141716A = CB1R antagonist; rimonabant = CB1R antagonist; capsazepine = transient receptor potential vanilloid type 1 antagonist; naloxone = opioid antagonist; flumazenil = GABAA receptor antagonist
Anxiolytic effects in models used: CER = reduced fear response; CFC = reduced conditioned freezing; CFC extinction = reduced freezing following extinction training; EPM = reduced % time in open arm; ETM = decreased inhibitory avoidance; L-DT = increased % time in light; VCT = increased licks indicating reduced conflict; NSF = reduced latency to feed; OF = increased % time in center; SI = increased social interaction
Anticomplusive effects: MBT = reduced burying
Panicolytic effects: ETM = decreased escape; GABAA blockade in dlSC = defensive immobility, and explosive escape; PAG-E-Stim = increased threshold for escape; PS = reduced explosive escape
WR = Wistar rats; SM = Swiss mice; L-E HR = Long–Evans hooded rats; i.p. = intraperitoneal; dlPAG = dorsolateral periaqueductal gray; i.c.v. = intracerebroventricular; PL = prelimbic; IL = infralimbic; BNST = bed nucleus of the stria terminalis; CeA = amygdala central nucleus; SNpr = substantia nigra pars reticularis; CUS = chronic unpredictable stress; GSCT = Geller–Seifter conflict test; CER = conditioned emotional response; EPM = elevated plus maze; VCT = Vogel conflict test; CFC = contextual fear conditioning; RS = restraint stress; ETM = elevated T maze; PAG E-stim = electrical stimulation of the dlPAG; L-DT = light–dark test; SI = social interaction; OF = open field; MBT = marble-burying test; PS = predator stress; NSF = novelty suppressed feeding test; GABAA = γ-aminobutyric acid receptor A; dlSC = deep layers superior colliculus; REM = rapid eye movement; NA = not applicable
Anxiolytic effects of CBD in models of generalized anxiety have been linked to specific receptor mechanisms and brain regions. The midbrain dorsal periaqueductal gray (DPAG) is integral to anxiety, orchestrating autonomic and behavioral responses to threat , and DPAG stimulation in humans produces feelings of intense distress and dread . Microinjection of CBD into the DPAG produced anxiolytic effects in the EPM, VGC, and ETM that were partially mediated by activation of 5-HT1ARs but not by CB1Rs [65, 68]. The bed nucleus of the stria terminalis (BNST) serves as a principal output structure of the amygdaloid complex to coordinate sustained fear responses, relevant to anxiety . Anxiolytic effects of CBD in the EPM and VCT occurred upon microinjection into the BNST, where they depended on 5-HT1AR activation , and also upon microinjection into the central nucleus of the amygdala . In the prelimbic cortex, which drives expression of fear responses via connections with the amygdala , CBD had more complex effects: in unstressed rats, CBD was anxiogenic in the EPM, partially via 5-HT1AR receptor activation; however, following acute restraint stress, CBD was anxiolytic . Finally, the anxiolytic effects of systemic CBD partially depended on GABAA receptor activation in the EPM model but not in the VCT model [61, 62].
As noted, CBD has been found to have a bell-shaped response curve, with higher doses being ineffective. This may reflect activation of TRPV1 receptors at higher dose, as blockade of TRPV1 receptors in the DPAG rendered a previously ineffective high dose of CBD as anxiolytic in the EPM . Given TRPV1 receptors have anxiogenic effects, this may indicate that at higher doses, CBD’s interaction with TRPV1 receptors to some extent impedes anxiolytic actions, although was notably not sufficient to produce anxiogenic effects.
Stress-induced Anxiety Models
Stress is an important contributor to anxiety disorders, and traumatic stress exposure is essential to the development of PTSD. Systemically administered CBD reduced acute increases in heart rate and blood pressure induced by restraint stress, as well as the delayed (24 h) anxiogenic effects of stress in the EPM, partially by 5-HT1AR activation [67, 73]. However intra-BNST microinjection of CBD augmented stress-induced heart rate increase, also partially via 5-HT1AR activation . In a subchronic study, CBD administered daily 1 h after predator stress (a proposed model of PTSD) reduced the long-lasting anxiogenic effects of chronic predator stress, partially via 5-HT1AR activation . In a chronic study, systemic CBD prevented increased anxiety produced by chronic unpredictable stress, in addition to increasing hippocampal AEA; these anxiolytic effects depended upon CB1R activation and hippocampal neurogenesis, as demonstrated by genetic ablation techniques . Prior stress also appears to modulate CBD’s anxiogenic effects: microinjection of CBD into the prelimbic cortex of unstressed animals was anxiogenic in the EPM but following restraint stress was found to be anxiolytic . Likewise, systemic CBD was anxiolytic in the EPM following but not prior to stress .
PD and Compulsive Behavior Models
CBD inhibited escape responses in the ETM and increased DPAG escape electrical threshold , both proposed models of panic attacks . These effects partially depended on 5-HT1AR activation but were not affected by CB1R blockade. CBD was also panicolytic in the predator–prey model, which assesses explosive escape and defensive immobility in response to a boa constrictor snake, also partially via 5-HT1AR activation; however, more consistent with an anxiogenic effect, CBD was also noted to decrease time spent outside the burrow and increase defensive attention (not shown in Table Table1) 1 ) [75, 86] . Finally, CBD, partially via CB1Rs, decreased defensive immobility and explosive escape caused by bicuculline-induced neuronal activation in the superior colliculus . Anticompulsive effects of CBD were investigated in marble-burying behavior, conceptualized to model OCD . Acute systemic CBD reduced marble-burying behavior for up to 7 days, with no attenuation in effect up to high (120 mg/kg) doses, and effect shown to depend on CB1Rs but not 5-HT1ARs [71, 74, 88].
Contextual Fear Conditioning, Fear Extinction, and Reconsolidation Blockade
Several studies assessed CBD using contextual fear conditioning. Briefly, this paradigm involves pairing a neutral context, the conditioned stimulus (CS), with an aversive unconditioned stimulus (US), a mild foot shock. After repeated pairings, the subject learns that the CS predicts the US, and subsequent CS presentation elicits freezing and other physiological responses. Systemic administration of CBD prior to CS re-exposure reduced conditioned cardiovascular responses , an effect reproduced by microinjection of CBD into the BNST, and partially mediated by 5-HT1AR activation . Similarly, CBD in the prelimbic cortex reduced conditioned freezing , an effect prevented by 5-HT1AR blockade . By contrast, CBD microinjection in the infralimbic cortex enhanced conditioned freezing . Finally, El Batsh et al.  reported that repeated CBD doses over 21 days, that is chronic as opposed to acute treatment, facilitated conditioned freezing. In this study, CBD was administered prior to conditioning rather than prior to re-exposure as in acute studies, thus further directly comparable studies are required.
CBD has also been shown to enhance extinction of contextually conditioned fear responses. Extinction training involves repeated CS exposure in the absence of the US, leading to the formation of a new memory that inhibits fear responses and a decline in freezing over subsequent training sessions. Systemic CBD administration immediately before training markedly enhanced extinction, and this effect depended on CB1R activation, without involvement of TRPV1 receptors . Further studies showed CB1Rs in the infralimbic cortex may be involved in this effect .
CBD also blocked reconsolidation of aversive memories in rat . Briefly, fear memories, when reactivated by re-exposure (retrieval), enter into a labile state in which the memory trace may either be reconsolidated or extinguished , and this process may be pharmacologically modulated to achieve reconsolidation blockade or extinction. When administered immediately following retrieval, CBD prevented freezing to the conditioned context upon further re-exposure, and no reinstatement or spontaneous recovery was observed over 3 weeks, consistent with reconsolidation blockade rather than extinction . This effect depended on CB1R activation but not 5-HT1AR activation .
Summary and Clinical Relevance
Overall, existing preclinical evidence strongly supports the potential of CBD as a treatment for anxiety disorders. CBD exhibits a broad range of actions, relevant to multiple symptom domains, including anxiolytic, panicolytic, and anticompulsive actions, as well as a decrease in autonomic arousal, a decrease in conditioned fear expression, enhancement of fear extinction, reconsolidation blockade, and prevention of the long-term anxiogenic effects of stress. Activation of 5-HT1ARs appears to mediate anxiolytic and panicolytic effects, in addition to reducing conditioned fear expression, although CB1R activation may play a limited role. By contrast, CB1R activation appears to mediate CBD’s anticompulsive effects, enhancement of fear extinction, reconsolidation blockade, and capacity to prevent the long-term anxiogenic consequences of stress, with involvement of hippocampal neurogenesis.
While CBD predominantly has acute anxiolytic effects, some species discrepancies are apparent. In addition, effects may be contingent on prior stress and vary according to brain region. A notable contrast between CBD and other agents that target the eCB system, including THC, direct CB1R agonists and FAAH inhibitors, is a lack of anxiogenic effects at a higher dose. Further receptor-specific studies may elucidate the receptor specific basis of this distinct dose response profile. Further studies are also required to establish the efficacy of CBD when administered in chronic dosing, as relatively few relevant studies exist, with mixed results, including both anxiolytic and anxiogenic outcomes.
Overall, preclinical evidence supports systemic CBD as an acute treatment of GAD, SAD, PD, OCD, and PTSD, and suggests that CBD has the advantage of not producing anxiogenic effects at higher dose, as distinct from other agents that enhance CB1R activation. In particular, results show potential for the treatment of multiple PTSD symptom domains, including reducing arousal and avoidance, preventing the long-term adverse effects of stress, as well as enhancing the extinction and blocking the reconsolidation of persistent fear memories.
Human Experimental and Clinical Studies
Evidence from Acute Psychological Studies
Relevant studies are summarized in Table Table2. 2 . The anxiolytic effects of CBD in humans were first demonstrated in the context of reversing the anxiogenic effects of THC. CBD reduced THC-induced anxiety when administered simultaneously with this agent, but had no effect on baseline anxiety when administered alone [99, 100]. Further studies using higher doses supported a lack of anxiolytic effects at baseline [101, 107]. By contrast, CBD potently reduces experimentally induced anxiety or fear. CBD reduced anxiety associated with a simulated public speaking test in healthy subjects, and in subjects with SAD, showing a comparable efficacy to ipsapirone (a 5-HT1AR agonist) or diazepam [98, 105]. CBD also reduced the presumed anticipatory anxiety associated with undergoing a single-photon emission computed tomography (SPECT) imaging procedure, in both healthy and SAD subjects [102, 104]. Finally, CBD enhanced extinction of fear memories in healthy volunteers: specifically, inhaled CBD administered prior to or after extinction training in a contextual fear conditioning paradigm led to a trend-level enhancement in the reduction of skin conductance response during reinstatement, and a significant reduction in expectancy (of shock) ratings during reinstatement .
Human psychological studies
Measure Effect Karniol et al.  HV,
Oral, 15, 30, 60 mg, alone or with THC,
acute, at 55, 95, 155, and 185 min
Anxiety and pulse rate after THC and at baseline ↓ THC-induced increases in subjective anxiety and pulse rate
No effect at baseline
Zuardi et al.,  HV,
Oral 1 mg/kg alone or with THC, acute, 80 min STAI score after THC ↓ THC-induced increases in STAI scores Zuardi et al.  HV,
Oral 300 mg,
acute, 80 min
VAMS, STAI and BP following SPST ↓ STAI scores
↓ VAMS scores
Martin-Santos et al.  HV,
Oral 600 mg,
acute, 1, 2, 3 h
Baseline anxiety and pulse rate No effect Crippa et al.  10 HV,
Oral 400 mg,
acute, 60 and 75 min
VAMS before SPECT
↓ VAMS scores Bhattacharyya et al.  15 HV
Oral 600 mg,
acute, 1, 2, 3 h
↓ STAI scores
↓ VAMS scores
Crippa et al.  SAD and HC
Oral 400 mg,
acute, 75 and 140 min
VAMS before SPECT
↓ VAMS scores Bergamaschi et al.  SAD and HC DBP Oral 600 mg, acute, 1, 2, 3 h VAMS, SSPS-N, cognitive impairment, SCR, HR after SPST ↓ VAMS, SSPS-N and cognitive impairment, no effect on SCR or HR Das et al.  HV
Inhaled, 32 mg, acute, immediately following, before, after extinction SCR and shock expectancy following extinction CBD after extinction training produced trend level reduction in SCR and decreased shock expectancy Hindocha et al.  Varying in schizotypy and cannabis use, DBP Inhaled, 16 mg, acute Baseline VAS anxiety No significant effect of CBD
HV = healthy volunteers; DBP = double-blind placebo; SAD = social anxiety disorder; HC = healthy controls; THC = Δ 9-tetrahydrocannabinol; STAI = Spielberger’s state trait anxiety inventory; VAMS = visual analog mood scale; BP = blood pressure; SPST = simulated public speaking test; SCR = skin conductance response; SPECT = single-photon emission computed tomography; SSPS-N = negative self-evaluation subscale; HR = heart rate; VAS = visual analog scale, CBD = cannabidiol
Evidence from Neuroimaging Studies
Relevant studies are summarized in Table Table3. 3 . In a SPECT study of resting cerebral blood flow (rCBF) in normal subjects, CBD reduced rCBF in left medial temporal areas, including the amygdala and hippocampus, as well as the hypothalamus and left posterior cingulate gyrus, but increased rCBF in the left parahippocampal gyrus. These rCBF changes were not correlated with anxiolytic effects . In a SPECT study, by the same authors, in patients with SAD, CBD reduced rCBF in overlapping, but distinct, limbic and paralimbic areas; again, with no correlations to anxiolytic effects .
Study Subjects, design CBD route, dose, timing Measure Effect of CBD Crippa et al.  10 HV,
Oral 400 mg,
acute, 60 and 75 min
SPECT, resting (rCBF) ↓ rCBF in left medial temporal cluster, including amygdala and HPC, also ↓ rCBF in the HYP and posterior cingulate gyrus
↑ rCBF in left PHG
Borgwardt et al.  15 HV,
Oral 600 mg,
acute, 1–2 h
fMRI during oddball and go/no-go task ↓ Activation in left insula, STG and MTG Fusar-Poli et al.  15 HV,
Oral 600 mg,
acute, 1–2 h
fMRI activation during fearful faces task ↓ Activation in left medial temporal region, including amygdala and anterior PHG, and in right ACC and PCC Fusar-Poli et al.  15 HV,
Oral 600 mg,
acute, 1–2 h
fMRI functional connectivity during fearful faces task ↓ Functional connectivity between L) AMY and ACC Crippa et al.  SAD and HC
Oral 400 mg,
acute, 75 and 140 min
SPECT, resting (rCBF) ↓ rCBF in the left PHG, HPC and ITG.
↑ rCBF in the right posterior cingulate gyrus
CBD = cannabidiol; HV = healthy controls; DBP = double-blind placebo; SAD = social anxiety disorder; HC = healthy controls; SPECT = single-photo emission computed tomography; rCBF = regional cerebral blood flow; fMRI = functional magnetic resonance imaging; HPC = hippocampus; HYP = hypothalamus; PHG = parahippocampal gyrus; STG = superior temporal gyrus; MTG = medial temporal gyrus; ACC = anterior cingulate cortex; PCC = posterior cingulate cortex
In a series of placebo-controlled studies involving 15 healthy volunteers, Fusar-Poli et al. investigated the effects of CBD and THC on task-related blood-oxygen-level dependent functional magnetic resonance imaging activation, specifically the go/no-go and fearful faces tasks [109, 110]. The go/no-go task measures response inhibition, and is associated with activation of medial prefrontal, dorsolateral prefrontal, and parietal areas . Response activation is diminished in PTSD and other anxiety disorders, and increased activation predicts response to treatment . CBD produced no changes in predicted areas (relative to placebo) but reduced activation in the left insula, superior temporal gyrus, and transverse temporal gyrus. The fearful faces task activates the amygdala, and other medial temporal areas involved in emotion processing, and heightened amygdala response activation has been reported in anxiety disorders, including GAD and PTSD [113, 114]. CBD attenuated blood-oxygen-level dependent activation in the left amygdala, and the anterior and posterior cingulate cortex in response to intensely fearful faces, and also reduced amplitude in skin conductance fluctuation, which was highly correlated with amygdala activation . Dynamic causal modeling analysis in this data set further showed CBD reduced forward functional connectivity between the amygdala and anterior cingulate cortex .
Evidence from Epidemiological and Chronic Studies
Epidemiological studies of various neuropsychiatric disorders indicate that a higher CBD content in chronically consumed cannabis may protect against adverse effects of THC, including psychotic symptoms, drug cravings, memory loss, and hippocampal gray matter loss [115–118] (reviewed in ). As THC acutely induces anxiety, this pattern may also be evident for chronic anxiety symptoms. Two studies were identified, including an uncontrolled retrospective study in civilian patients with PTSD patients , and a case study in a patient with severe sexual abuse-related PTSD , which showed that chronic cannabis use significantly reduces PTSD symptoms; however, these studies did not include data on the THC:CBD ratio. Thus, overall, no outcome data are currently available regarding the chronic effects of CBD in the treatment of anxiety symptoms, nor do any data exist regarding the potential protective effects of CBD on anxiety potentially induced by chronic THC use.
Summary and Clinical Relevance
Evidence from human studies strongly supports the potential for CBD as a treatment for anxiety disorders: at oral doses ranging from 300 to 600 mg, CBD reduces experimentally induced anxiety in healthy controls, without affecting baseline anxiety levels, and reduces anxiety in patients with SAD. Limited results in healthy subjects also support the efficacy of CBD in acutely enhancing fear extinction, suggesting potential for the treatment of PTSD, or for enhancing cognitive behavioral therapy. Neuroimaging findings provide evidence of neurobiological targets that may underlie CBD’s anxiolytic effects, including reduced amygdala activation and altered medial prefrontal amygdala connectivity, although current findings are limited by small sample sizes, and a lack of independent replication. Further studies are also required to establish whether chronic, in addition to acute CBD dosing is anxiolytic in human. Also, clinical findings are currently limited to SAD, whereas preclinical evidence suggests CBD’s potential to treat multiple symptom domains relevant to GAD, PD, and, particularly, PTSD.
Preclinical evidence conclusively demonstrates CBD’s efficacy in reducing anxiety behaviors relevant to multiple disorders, including PTSD, GAD, PD, OCD, and SAD, with a notable lack of anxiogenic effects. CBD’s anxiolytic actions appear to depend upon CB1Rs and 5-HT1ARs in several brain regions; however, investigation of additional receptor actions may reveal further mechanisms. Human experimental findings support preclinical findings, and also suggest a lack of anxiogenic effects, minimal sedative effects, and an excellent safety profile. Current preclinical and human findings mostly involve acute CBD dosing in healthy subjects, so further studies are required to establish whether chronic dosing of CBD has similar effects in relevant clinical populations. Overall, this review emphasizes the potential value and need for further study of CBD in the treatment of anxiety disorders.