Cannabidiol
Viewing r1 — May 7, 2026 — CURRENT
Back to HistoryInteractions, related substances, and reports reflect the current entry and are not shown for historical revisions.
CBD (cannabidiol) is a naturally-occurring cannabinoid of the terpenophenolic class. It is the principal non-intoxicating compound in cannabis, distinguished from Δ⁹-THC by its absence of euphoria or cognitive impairment. CBD is a polypharmacological modulator, producing its effects by engaging serotonin receptors, endocannabinoid signaling, and ion channels without directly activating CB1.
Psychedex is in open beta. We are still fine-tuning the generation and review process. Please double-check sources.
First isolated from cannabis in 1940 by Roger Adams, CBD's structure was elucidated by Raphael Mechoulam in 1963 — before THC itself was identified. Dramatic pediatric epilepsy cases drove clinical investment, culminating in a pivotal trial demonstrating 38.9% seizure reduction in Dravet syndrome and FDA approval of Epidiolex in 2018.[1] Active investigation now spans anxiety disorders, schizophrenia, substance use disorders, and autism spectrum disorder.[2]
Subjective effects include anxiety suppression, sedation, muscle relaxation, and pain suppression. The experience is one of symptom attenuation rather than altered consciousness — a quiet reduction of tension and discomfort without euphoria, perceptual change, or cognitive shift. Somnolence, diarrhea, and appetite changes are characteristic unsought effects.
CBD produces no physical dependence, no tolerance, and no withdrawal at any studied dose; liver toxicity is the principal dose-limiting concern, particularly with valproate co-administration.[3] The primary interaction risk stems from inhibition of a liver enzyme (CYP2C19) that metabolizes common medications, elevating their blood levels. Decades of clinical epilepsy data provide a strong safety foundation, though long-term effects in non-epilepsy populations remain incompletely characterized.
History[edit]
Discovery
Roger Adams first isolated cannabidiol from cannabis in 1940; Alexander Todd achieved the isolation independently around the same time.[4][5][6] The compound's full structure remained unresolved for over two decades until Raphael Mechoulam determined its (1R,6R) stereochemistry in 1963 — a year before he identified Δ⁹-THC as the primary intoxicating constituent of cannabis.[4][5] That finding recast CBD as a pharmacologically distinct, non-psychoactive cannabinoid and set the trajectory for all subsequent research.
Clinical breakthrough
CBD attracted limited clinical attention for decades, with small studies in the 1970s and 1980s suggesting anticonvulsant and anxiolytic properties but failing to advance beyond exploratory stages.[5][7] Public interest surged in 2013 when CNN documented a child with Dravet syndrome responding to a high-CBD cannabis extract called "Charlotte's Web," catalyzing pharmaceutical investment from GW Pharmaceuticals. In 2017, Devinsky et al. published the landmark Phase 3 result: a 38.9% median reduction in convulsive seizures versus 13.3% for placebo in Dravet syndrome,[1] followed by a companion trial for Lennox-Gastaut syndrome.[8]
Regulatory milestones
The FDA approved Epidiolex on June 25, 2018 — the first plant-derived cannabinoid prescription medicine in the United States — for Dravet syndrome and Lennox-Gastaut syndrome. The 2018 Farm Bill legalized hemp-derived CBD at the federal level, though the FDA continued to prohibit its use in foods and dietary supplements. Australia's TGA approved Epidyolex in September 2020, the FDA expanded approval to tuberous sclerosis complex in 2021, and by 2026 EFSA had published a provisional safe dose of 0.0275 mg/kg bw/day for food supplement contexts — substantially below clinical dosing ranges.[3]
The name cannabidiol derives from Cannabis (the plant genus) and the chemical suffix -diol, indicating its two hydroxyl groups. In consumer culture, "CBD" has become a near-universal abbreviation, appearing on products from tinctures to pet treats. The compound's non-intoxicating reputation drove an explosion of unregulated consumer products following the 2018 Farm Bill, creating a market where quality varies enormously and therapeutic claims routinely outpace evidence.
Chemistry[edit]
Structural class
Cannabidiol belongs to the terpenophenolic phytocannabinoids — compounds built from a resorcinol ring linked to a monoterpene unit. Unlike Δ⁹-THC, CBD lacks the pyran ring closure that enables direct binding at CB1's main active site. The cyclohexene ring remains open, and this single structural difference accounts for the compound's entirely non-intoxicating character. A pentyl side chain at C-5 of the resorcinol ring is shared with THC and other classical cannabinoids.
Molecular identity
| Molecular formula | C₂₁H₃₀O₂ |
| Molecular weight | 314.5 g/mol |
The molecule consists of a resorcinol ring bearing two hydroxyl groups and a pentyl chain, connected to a cyclohexene ring carrying a methyl group and an isopropenyl substituent. The absence of pyran ring closure — where THC has a fused oxygen bridge — eliminates the molecular geometry required for direct CB1 activation.
Stereochemistry
CBD has two stereocenters on the cyclohexene ring, producing two possible mirror-image forms. The naturally occurring enantiomer is (-)-CBD with (1R,6R) configuration, established by Mechoulam in 1963. The unnatural (+)-CBD shows substantially higher affinity at cannabinoid receptors and a distinct pharmacological profile.[9] All approved pharmaceutical products use (-)-CBD.
Physical properties
CBD is highly fat-soluble (LogP ~6.3) and practically insoluble in water.[10][11] This extreme lipophilicity drives the requirement for oil-based or nanoemulsion formulations and explains the pronounced food effect on absorption. The compound degrades under light, heat, and acidic conditions; pharmaceutical formulations require UV protection and storage below 25°C.
Pharmacology[edit]
Mechanism of action
CBD acts at no fewer than six molecular targets without functioning as a direct cannabinoid receptor agonist — a polypharmacological profile that distinguishes it from nearly all other cannabinoids.[9][12]
At CB1 receptors, CBD does not bind the main active site but modulates it from an allosteric position, subtly reducing the receptor's response to other cannabinoids.[13][14] At serotonin 5-HT₁A receptors, it acts as a partial agonist — engaging the same target as the anxiolytic buspirone — which underlies its anxiety-reducing and anti-nausea effects.[15][12][16]
CBD activates TRPV1 channels with potency comparable to capsaicin, then desensitizes them — a mechanism contributing to pain suppression and anti-inflammatory effects.[9][17] It antagonizes GPR55, reducing neuronal excitability in a pathway relevant to seizure suppression.[18][19]
CBD inhibits adenosine reuptake, raising levels of this naturally inhibitory signaling molecule,[20] and weakly blocks FAAH, the enzyme that breaks down anandamide — the body's own cannabinoid.[9][17] In a clinical schizophrenia trial, CBD treatment elevated blood anandamide levels, and the degree of elevation correlated with symptom improvement.[21] CBD also activates the pregnane X receptor (PXR), inducing CYP3A4 expression — a mechanism relevant to drug-drug interactions.[22]
Pharmacokinetics
Oral bioavailability is low and highly variable (6–20%) due to extensive first-pass liver metabolism.[3] High-fat meals dramatically increase absorption; Epidiolex is dosed with food. Time to peak blood levels ranges from 1.5 to 5 hours depending on formulation and fed or fasted state.
CBD distributes extensively into body tissues, reflecting its high fat solubility. It is heavily protein-bound in blood (greater than 94%) and crosses both the blood-brain barrier and the placenta.[3] A meaningful fraction (11–20%) reaches the bloodstream via lymphatic transport, partially bypassing first-pass metabolism.[23]
The liver metabolizes CBD primarily through CYP2C19 and CYP3A4, producing 7-hydroxy-CBD (a pharmacologically active metabolite) and 7-carboxy-CBD (the major circulating metabolite with less activity). Genetic variation in CYP2C19 creates substantial differences between individuals.[18][24]
Plasma half-life is approximately 9 hours after a single dose and extends to 18–32 hours with repeated use, though subjective effects typically last only 1.5–4 hours.
Neuroscience[edit]
Where it acts
CBD modulates brain function through endocannabinoid, serotonergic, and ion-channel pathways — not through direct CB1 activation like THC. By raising anandamide levels through FAAH inhibition, CBD strengthens the brain's own cannabinoid signaling.[9] In the amygdala, this reduces fear-conditioned responses; in the hippocampus, it modulates memory encoding and extinction learning.
The clinical finding that CBD-induced anandamide elevation correlates with antipsychotic improvement in schizophrenia[21] confirms endocannabinoid augmentation as a proximate mechanism for at least some of CBD's neuropsychiatric effects. CBD's partial activation of 5-HT₁A serotonin receptors in the raphe nuclei engages the same autoreceptor feedback loops targeted by buspirone-class anxiolytics,[12] while its anti-nausea effects also operate through this receptor.[25][26]
Why it matters
CBD's efficacy in treatment-resistant epilepsy — where single-target drugs fail — illustrates the value of its multi-target mechanism.[27] Seizure suppression converges from GPR55 antagonism reducing excitatory transmission,[18] TRPV1 desensitization dampening calcium-driven excitability, and elevated adenosine activating inhibitory receptors.[20] Anti-neuroinflammatory effects — including suppression of microglial activation — may add neuroprotection in epileptic networks.[19]
The endocannabinoid system also buffers stress through the HPA axis. CBD's combined serotonin receptor activation and anandamide augmentation position it as a stress-buffering agent, providing a framework for its broad anxiolytic effects without the sedation or dependence of GABAergic drugs.citation needed
The optimal dose range for non-epilepsy applications remains unestablished, and whether the inverted U-shaped dose-response curve seen in animal anxiety models applies to human psychiatric outcomes is unresolved. Given CBD's low bioavailability and heavy protein binding, whether sufficient free drug reaches brain serotonin receptors at clinical doses has not been directly measured in humans.
Subjective Effects[edit]
CBD's experiential character is defined by absence: no euphoria, no perceptual distortion, no cognitive impairment. The subjective experience is one of symptom attenuation — reduced anxiety, decreased muscle tension, mild sedation — rather than an altered state of consciousness. Across the dose range, effects shift in intensity but not in kind: higher doses produce more pronounced sedation and relaxation without introducing qualitatively new experiential territory. Individual responses vary substantially due to the compound's low and variable oral bioavailability, and co-administration with food meaningfully increases the effect.
Compared to Δ⁹-THC, CBD occupies an entirely separate experiential category — closer in character to buspirone or a mild adaptogen than to a traditional cannabinoid. Where THC produces dose-dependent euphoria, time alteration, and appetite stimulation, CBD produces anxiolysis and physical calming without hedonic or perceptual alteration.
Effect Grid
Moderate anxiety suppression and mild sedation characterize the common dose range. Muscle relaxation becomes clearly noticeable. This is the range most commonly used in wellness and supplement contexts for general anxiolysis and stress reduction. CBD remains non-intoxicating — no euphoria, no altered perception, no cognitive impairment.
Mild drowsiness may emerge, particularly when taken with food (which increases bioavailability) or in the evening. Faint pain suppression may be perceptible in individuals with mild chronic pain. No significant gastrointestinal effects at this range for most users.
Subjective effects last approximately 1.5–4 hours. The anxiolytic dose-response may follow an inverted U-curve — higher doses are not necessarily more effective for anxiety reduction.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Constipation · Dizziness · Physical fatigue · Appetite suppression · Dry mouth · Headache · Nausea · Wakefulness · Vomiting
Dry mouth · Headache · Nausea · Wakefulness · Vomiting
Timeline
Initial subtle anxiolysis begins — a faint softening of baseline tension that may be difficult to distinguish from placebo at lower doses. No perceptual or cognitive changes.
Anxiety reduction deepens and mild relaxation emerges. Muscle tension begins to ease. Effects remain subtle and non-intoxicating.
Maximum anxiolysis and sedation. Muscle relaxation is most pronounced. Mild drowsiness may be present at common doses and above.
Effects gradually diminish. Residual calm and muscle relaxation persist. Sedation tapers but drowsiness may linger, particularly at higher doses.
Mild residual relaxation and improved sleep quality in evening doses. Active metabolite 7-OH-CBD contributes to extended pharmacological activity beyond the subjective window.
⚠ Avoid driving or operating machinery if sedation persists, particularly at doses above 30 mg.
Safety[edit]
- Acute toxicity
- Negligible
- Chronic toxicity
- Moderate
- Withdrawal
- None
- Tolerance buildup
- none
- Tolerance reset
- —
- Physical
- None
- Psychological
- None
- Compulsive redosing
- Negligible
- Dose escalation
- Negligible
- Cross-tol.
- —
Toxicity
CBD has a wide safety margin at clinical doses. No human lethal dose has been established, and doses up to 1,500 mg/day have been administered in studies without acute toxicity. At 300 mg/day for 14 days, adverse effects were mild with no significant difference from placebo.[28]
Liver toxicity
Liver toxicity is the principal dose-limiting risk for CBD. Liver function monitoring is required during treatment with pharmaceutical CBD (Epidiolex), particularly when co-administered with valproate.
EFSA identified liver toxicity as a consistent finding in animal studies and set a provisional safe dose of 0.0275 mg/kg bw/day (approximately 2 mg/day) for food supplement contexts.[3] This figure reflects the conservative margin applied to food safety assessments, not a clinical dosing limit.
In healthy athletes, 60 mg/day for seven days produced no liver effects and inhibited exercise-induced liver enzyme elevation.[29] The lowest dose at which liver effects have been observed in humans is approximately 300 mg/day.[29] In epilepsy trials, elevated liver enzymes were observed, confounded by but not fully explained by valproate co-administration.[30]
Liver function tests should be obtained at baseline and at 1, 3, and 6 months during treatment.[31][32]
Gastrointestinal effects
Diarrhea (11.9% incidence in expanded access programs), nausea, and appetite changes are common at clinical doses.[31][28]
Reproductive and developmental toxicity
EFSA concluded that CBD safety cannot be established for pregnant or lactating women, individuals under 25 (except for approved medical indications), or those on concurrent medications.[3] CBD crosses the placenta, and animal studies demonstrate reproductive toxicity and neurodevelopmental effects. No controlled human reproductive data exist.
Endocrine and cardiovascular effects
Animal studies show altered thyroid hormone levels and adrenal changes.[3] Human endocrine effects at clinical doses have not been systematically studied.
CBD does not produce the rapid heart rate characteristic of THC, and no significant cardiovascular adverse effects are documented at therapeutic doses.[33] CBD is not a respiratory depressant.
Psychological risks
CBD does not produce psychological distress, psychotic symptoms, or cognitive impairment at any studied dose. It has demonstrated antipsychotic properties, significantly improving positive psychotic symptoms in a clinical schizophrenia trial.[34]
Somnolence is the most common neuropsychiatric adverse effect, occurring in 22.6% of epilepsy patients with dose-dependent severity.[31] This warrants caution regarding driving and operating machinery. No cases of persistent perceptual changes or psychiatric destabilization have been attributed to CBD.
Tolerance and dependence
No tolerance develops to CBD's anticonvulsant effects. Long-term extension trials demonstrate sustained seizure reduction without dose escalation over years of continuous treatment.[27][35][36] This distinguishes CBD from THC, which produces tolerance through CB1 downregulation.
No physical or psychological dependence has been documented at any dose.[37] No withdrawal has been described after discontinuation; in combination products containing both CBD and THC, any dependence signals are attributed to the THC component.[38] The DEA's Schedule V placement of Epidiolex reflects regulatory consensus that CBD has essentially no abuse potential.
Drug interactions
CBD's most important drug interactions stem from its inhibition of CYP2C19, a liver enzyme that metabolizes many common medications.
The most clinically significant interaction is with clobazam. CBD elevates levels of clobazam's active metabolite, often requiring clobazam dose reduction.[39][40] CBD similarly increases citalopram exposure,[41] with implications for anyone taking SSRIs. Other affected medications include proton pump inhibitors and diazepam.
Chronic CBD use can convert a person's CYP2C19 metabolizer status from normal to functionally poor, affecting the processing of other drugs beyond those taken alongside CBD.[24]
CBD activates human PXR, which can theoretically induce CYP3A4 and reduce levels of medications metabolized by that enzyme.[22] However, clinical trials found this did not significantly affect CYP3A4 activity in practice, while CYP3A4 inducers (rifampicin, phenytoin) reduced CBD levels.[39]
Co-administration with valproate produces elevated liver enzymes through an incompletely understood mechanism.[39] Additive sedation occurs with benzodiazepines, opioids, and other central nervous system depressants.
No cases of serotonin syndrome from CBD alone or with SSRIs have been reported. The primary SSRI interaction is pharmacokinetic — elevated SSRI levels via CYP2C19 inhibition — which could indirectly increase serotonergic tone.
Contraindications
Absolute contraindications:
- Pregnancy and lactation. CBD crosses the placenta; animal studies demonstrate developmental toxicity. EFSA concludes safety cannot be established.[3]
- Severe liver disease. Pre-existing liver impairment increases the risk of CBD-induced liver toxicity given the compound's hepatic metabolism.
Relative contraindications:
- Concurrent valproate therapy without liver function monitoring.[32]
- Concurrent CYP2C19 substrate medications without dose adjustment, including clobazam, citalopram, and diazepam.[39][41]
- Age under 25 for non-medical use. EFSA concludes safety has not been established for this population outside approved indications.[3]
- Concurrent strong CYP3A4 inducers. Rifampicin, phenytoin, and carbamazepine reduce CBD blood levels, potentially rendering it ineffective.[39]
Harm Reduction[edit]
Forms & Identification
CBD products span a vast quality spectrum, from pharmaceutical-grade Epidiolex (standardized at 100 mg/mL oral solution) to unregulated tinctures, capsules, edibles, topicals, and vape liquids. Products sold outside the pharmaceutical supply chain vary widely in actual CBD content — independent testing has repeatedly found products containing substantially less CBD than labeled, as well as unlabeled THC and other contaminants. A third-party certificate of analysis from an accredited laboratory is essential for any consumer-grade product.
Isolate, broad-spectrum, and full-spectrum formulations differ in their content of other cannabinoids. Full-spectrum products contain trace THC (up to 0.3%) which may be sufficient to trigger a positive drug test.
Guidelines
- Start with a low dose (5–10 mg) and increase gradually over days, not hours
- Take oral CBD with food — a meal containing fat substantially increases absorption
- Use products with a current third-party certificate of analysis from an accredited laboratory
- If taking prescription medications, consult a pharmacist or physician about potential interactions before starting CBD — particularly if taking clobazam, valproate, SSRIs, or benzodiazepines
- Monitor for excessive drowsiness, especially when combined with other sedating substances
- If using CBD at clinical doses (above 100 mg/day), request baseline liver function tests and periodic monitoring
Set & Setting
CBD does not alter consciousness, so set and setting considerations are minimal compared to psychoactive substances. The primary practical consideration is timing: CBD's sedative effects at higher doses can impair alertness, making evening dosing preferable for those sensitive to drowsiness. Because bioavailability varies substantially between individuals and formulations, responses to the same labeled dose can differ — start with the lowest available dose and assess effects before increasing.
Aftercare & integration. CBD does not produce altered states requiring formal integration. Post-use considerations are practical: if sedation was pronounced, allow adequate sleep recovery before driving or operating machinery. Those using CBD for anxiety or sleep should track their response over at least a week before adjusting doses, as effects may shift with accumulation given the compound's long half-life (18–32 hours with repeated dosing).
If discontinuing after sustained use at high doses, tapering is not pharmacologically necessary — no withdrawal has been documented — but gradual reduction may help distinguish returning symptoms from discontinuation effects.
Recovery & Support
CBD does not produce dependence or compulsive use patterns. However, individuals using CBD as a substitute for evidence-based treatments for anxiety, depression, or chronic pain should periodically reassess whether it is providing meaningful benefit. If CBD is being used to manage symptoms of an underlying condition, professional evaluation ensures that effective treatments are not being delayed or replaced. For those using CBD alongside recovery from other substance dependencies, disclosure to treatment providers ensures accurate medication interaction assessment.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
CBD alone has not produced life-threatening toxicity in any documented case. However, contaminated or mislabeled products — or interactions with other substances — can create emergencies.
Recognizing a problem:
- Severe drowsiness or unresponsiveness beyond normal sedation
- Signs of allergic reaction (difficulty breathing, swelling, hives)
- Yellowing of skin or eyes, dark urine, or persistent nausea (signs of liver injury — seek medical attention)
If someone is unresponsive:
- 1. Call emergency services
- 2. Place the person on their side (recovery position)
- 3. Do not induce vomiting
- 4. Stay with the person until help arrives
What to tell the dispatcher: the substance taken (CBD product, with brand if known), the amount, when it was taken, any other substances or medications involved, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during drug-related emergencies.
Legal Status[edit]
CBD occupies a fragmented regulatory landscape where legal status depends on the source plant (hemp versus marijuana), intended use (food supplement, prescription medicine, or consumer product), and jurisdiction. The 2020 European Court of Justice ruling that CBD is not a narcotic under international conventions established an important precedent, but national regulations continue to vary widely. The 2018 US Farm Bill legalized hemp-derived CBD at the federal level, while the FDA simultaneously maintained that CBD cannot be added to foods or marketed as a dietary supplement due to its status as an approved drug ingredient.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States (hemp-derived) | Legal (2018 Farm Bill) | Hemp-derived CBD (from cannabis with less than 0.3% THC) is federally legal. FDA prohibits addition to foods, beverages, or dietary supplements due to CBD's approved drug status[42] |
| United States (Epidiolex) | Schedule V (DEA, 2018); rescheduled to Schedule III (April 2026) | Prescription required; approved for Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex |
| United Kingdom | Legal without prescription | Novel food regulations apply; products exceeding 1 mg THC per package are restricted. Epidiolex available on NHS prescription for severe pediatric epilepsy |
| European Union | Generally permitted; novel food status | ECJ ruled CBD is not a narcotic (2020). Novel food authorization pending for food supplements as of 2026[3] |
| Canada | Regulated under Cannabis Act (2018) | Requires licensed producers. CBD products fall under cannabis regulation; hemp exemptions apply under threshold conditionscitation needed |
| Australia | Schedule 4 (prescription); Schedule 3 (OTC, theoretical) | TGA down-scheduled low-dose CBD to Schedule 3 (OTC) in December 2020 but no OTC products registered as of 2026. Epidyolex TGA-approved September 2020; PBS-listed for Dravet syndrome from May 2021 |
CBD products sold outside the pharmaceutical supply chain vary widely in actual CBD content and may contain unlabeled THC or contaminants. Third-party certificate-of-analysis testing is recommended for consumer-grade products. Pharmaceutical-grade CBD (Epidiolex/Epidyolex) is standardized at 100 mg/mL oral solution.
references
- [1] ^abDevinsky O, Cross JH, Laux L, et al. (2017) Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome — New England Journal of Medicine doi:10.1056/nejmoa1611618
- [2] ^O'Sullivan SE, Jensen SS, Nikolajsen GN, et al. (2023) The therapeutic potential of purified cannabidiol — Journal of Cannabis Research doi:10.1186/s42238-023-00186-9
- [3]
- [4] ^abPertwee RG (2006) Cannabinoid pharmacology: the first 66 years — British Journal of Pharmacology PMID:16402100
- [5] ^abcZuardi AW (2008) Cannabidiol: from an inactive cannabinoid to a drug with wide spectrum of action — Revista Brasileira de Psiquiatria PMID:18833429
- [6] ^Hanus LO, Meyer S, Munoz E, Taglialatela-Scafati O, Appendino G (2016) Phytocannabinoids: a unified critical inventory — Natural Product Reports doi:10.1039/c6np00074f