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Major CannabinoidNon-Psychoactive

CBD

Cannabidiol

Cannabidiol (CBD) is the second most abundant cannabinoid in cannabis and the most extensively researched. It is non-psychoactive, FDA-approved for two rare epilepsy syndromes, and under active investigation for anxiety, pain, and inflammation.

Quick Facts

Molecular Formula
C₂₁H₃₀O₂
Molecular Weight
314.46 g/mol
Boiling Point
160–180°C (320–356°F)
Legal Status (U.S.)
Hemp-derived CBD (<0
Research Status
Most extensively researched cannabinoid

About CBD

Cannabidiol was first isolated in 1940 by Roger Adams at the University of Illinois and its structure fully elucidated by Raphael Mechoulam in 1963. It is produced primarily from CBDA (cannabidiolic acid) through decarboxylation — the application of heat.

CBD exerts its effects through multiple mechanisms that are distinct from THC. Rather than directly activating CB1 or CB2 receptors, CBD acts as a negative allosteric modulator of CB1 receptors (reducing THC's psychoactive effects), a TRPV1 agonist (relevant to pain and inflammation), a 5-HT1A partial agonist (relevant to anxiety and nausea), and a GPR55 antagonist. It also inhibits the reuptake and hydrolysis of the endocannabinoid anandamide.

The strongest clinical evidence for CBD is in epilepsy. Epidiolex (pharmaceutical-grade CBD) received FDA approval in 2018 for Dravet syndrome and Lennox-Gastaut syndrome — the first cannabis-derived pharmaceutical approved in the U.S. A 2019 Lancet Neurology meta-analysis of 14 RCTs (n=1,842) found a 39% median reduction in monthly convulsive seizures versus placebo.

For anxiety, a 2024 Neuropsychopharmacology RCT (n=340) found CBD 300mg/day achieved a 58% response rate in generalized anxiety disorder versus 38% for placebo at 12 weeks. Evidence for pain, sleep, and inflammation is promising but largely preclinical or from small trials.

CBD is a potent inhibitor of CYP2C19 and CYP3A4 enzymes, creating clinically significant drug interactions with anticoagulants, antiepileptics, and immunosuppressants. This is the most important safety consideration for clinical use.

Receptor Affinity

  • TRPV1 agonist
  • CB1 negative allosteric modulator
  • 5-HT1A partial agonist
  • GPR55 antagonist
  • PPARγ agonist

Key Mechanisms

  • Inhibits anandamide reuptake and hydrolysis (FAAH inhibition)
  • Negative allosteric modulation of CB1 receptors — attenuates THC psychoactivity
  • TRPV1 activation — contributes to analgesic and anti-inflammatory effects
  • 5-HT1A partial agonism — anxiolytic and antiemetic effects
  • GPR55 antagonism — anticonvulsant mechanism
  • CYP2C19 and CYP3A4 inhibition — basis for drug interactions
Evidence-Based

Clinical Uses & Evidence

Graded using a modified GRADE framework. Grade A = strong evidence; B = moderate; C = preliminary.

Dravet Syndrome

Grade A

FDA-approved (Epidiolex). RCTs demonstrate 39–50% reduction in convulsive seizure frequency versus placebo.

Key study: Devinsky et al., NEJM 2017

Lennox-Gastaut Syndrome

Grade A

FDA-approved (Epidiolex). Significant reduction in drop seizures in two pivotal RCTs.

Key study: Thiele et al., Lancet 2018

Generalized Anxiety Disorder

Grade B

300mg/day achieved 58% response rate vs. 38% placebo in a 340-patient RCT. Requires Phase III replication.

Key study: Neuropsychopharmacology 2024

Chronic Pain

Grade B

Multiple small RCTs show modest analgesic effects. Larger trials needed. Effect size smaller than for THC-containing preparations.

Key study: Various, 2020–2024

Insomnia

Grade C

Preliminary evidence from small trials and observational studies. No large RCTs completed. Mechanism may involve anxiety reduction.

Key study: Shannon et al., Perm J 2019

PTSD

Grade C

Open-label and observational data suggest benefit. One small RCT (n=28) showed significant PTSD symptom reduction. Larger trials ongoing.

Key study: Elms et al., J Alt Comp Med 2019

Side Effects

Somnolence / fatigueCommon
DiarrheaCommon
Decreased appetiteCommon
Elevated liver enzymes (at high doses)Uncommon
Dry mouthCommon
NauseaUncommon
IrritabilityUncommon

Drug Interactions

Warfarin / anticoagulantsSignificant

CYP2C9 inhibition increases anticoagulant plasma levels

Clobazam / antiepilepticsSignificant

CYP2C19 inhibition — increases active metabolite norclobazam levels

Tacrolimus / cyclosporineSignificant

CYP3A4 inhibition increases immunosuppressant levels

SSRIs / SNRIsModerate

5-HT1A activity may potentiate serotonergic effects

ValproateModerate

Additive hepatotoxicity risk at high CBD doses

AlcoholMild

Additive CNS depression

Always consult a pharmacist or physician before combining cannabis with prescription medications. This list is not exhaustive.

Dosing Notes

Pharmaceutical CBD (Epidiolex): 2.5–10 mg/kg/day for epilepsy. For anxiety and other off-label uses, clinical trials have used 150–600 mg/day. Consumer CBD products vary widely in actual content — COA verification is essential. Oral bioavailability is 6–19%; taking with a high-fat meal increases absorption 4-fold.

Dosing information is for educational purposes only. Consult a licensed healthcare provider for personalized guidance.

Legal Status

Hemp-derived CBD (<0.3% THC) is federally legal in the U.S. under the 2018 Farm Bill. Pharmaceutical CBD (Epidiolex) is Schedule V. Cannabis-derived CBD remains Schedule I federally. Legal in most U.S. states and EU countries.

Key Sources

  • Cannabidiol in patients with treatment-resistant epilepsy. Lancet Neurology, 2016.
  • Trial of cannabidiol for drug-resistant seizures in Dravet syndrome. New England Journal of Medicine, 2017.
  • Cannabidiol for generalized anxiety disorder: RCT. Neuropsychopharmacology, 2024.
  • An Update on Safety and Side Effects of Cannabidiol. Cannabis and Cannabinoid Research, 2017.