Supplement: CBD (Cannabidiol)

What It Is

CBD, or cannabidiol, is one of the two main compounds in the cannabis plant. Unlike THC, the other one, it does not make you high. It is sold in two very different forms that often get discussed as if they were the same product:

• Prescription cannabidiol (Epidiolex) is a purified pharmaceutical liquid approved for specific rare epilepsies, made to a known strength and tested in randomized trials.
• Over-the-counter hemp CBD is the oils, gummies, capsules, and creams sold as supplements. It is held to no such manufacturing standard, and it carries almost none of the trial evidence people assume it does.

Almost all of the seizure trials, the anxiety experiments, and the liver-enzyme findings used the purified form at a controlled dose, often far higher than a supplement delivers. A strong result for Epidiolex does not transfer to a retail gummy of uncertain content.

What It Does

At the strong end are three rare epilepsies, where a purified prescription form reduced seizures in randomized trials. In Dravet syndrome, a severe childhood epilepsy, a trial of 120 children cut monthly convulsive seizures by about 39%, against about 13% on placebo. In Lennox-Gastaut syndrome, two trials reduced drop seizures by roughly 42 to 44%, against 17 to 22%. In tuberous sclerosis complex, a trial of 224 patients cut seizures by about 48%, against about 27%. These results made cannabidiol a medicine. They are narrow by design, these specific syndromes, at a controlled dose. They do not show a general sedative or brain-calming effect.

Below that is acute, situational anxiety, on thinner evidence. In small experiments, people took a single dose before a simulated public-speaking test. A 300 mg dose lowered the anxiety spike, while 150 mg and 600 mg did not, an inverted-U where more is not better. This says nothing yet about a daily gummy for an anxiety disorder over months, which has barely been tested. Still, the single-dose signal is an early but real result, worth watching as the research matures.

At the weak end are chronic pain and sleep, the two most-marketed uses. The best systematic review of cannabis-based products rated any pain benefit small, and the CBD-alone data thinner still. For sleep, most of what exists is uncontrolled case reports, and Western trials have not shown a reliable effect.

The Research & Studies

Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.

Seizure Control

Purified CBD cut monthly convulsive seizures about 39% in Dravet syndrome, versus 13% on placeboStrong

In plain terms

In a rigorous trial of children with a severe form of epilepsy, a purified prescription form of CBD cut convulsive seizures by roughly 39%, while placebo cut them by about 13%. This is the strongest and best-established use of cannabidiol.

In detail

This double-blind placebo-controlled randomized trial added cannabidiol oral solution (20 mg/kg/day) or placebo to standard antiepileptic treatment. Beyond seizure counts, more participants on cannabidiol were rated improved on a global impression scale. Adverse effects were more common on cannabidiol and included somnolence, diarrhea and raised liver aminotransferases, the last more frequent in those also taking valproate. The result was replicated and underpins the drug's regulatory approval for Dravet syndrome.

Who this may not transfer to:Dravet syndrome affects both sexes and the trial enrolled both; the anticonvulsant effect is not sex-specific.

How to use it

This is a prescription medicine used under a neurologist for a specific rare epilepsy, with liver monitoring and attention to drug interactions, not a reason to expect a retail CBD product to control seizures. The dose is high and the population narrow.

The study · 1

Devinsky et al., Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome · N Engl J Med 2017;376(21):2011-2020

Prescription CBD cut drop seizures 42 to 44% in Lennox-Gastaut syndrome, versus 17 to 22% on placeboStrong

In plain terms

In two solid trials of another rare childhood epilepsy, prescription CBD roughly halved the drop-type seizures for many patients, clearly more than placebo. This is the second well-established seizure use.

In detail

Both trials added cannabidiol oral solution to existing antiepileptic drugs in patients with Lennox-Gastaut syndrome. The 10 mg/kg dose in the Devinsky trial worked nearly as well as 20 mg/kg with fewer side effects, suggesting a lower dose can suffice. As in Dravet syndrome, somnolence, decreased appetite, diarrhea and raised liver enzymes were the notable adverse effects, and liver-enzyme elevations were more common with concomitant valproate.

Who this may not transfer to:Both trials enrolled both sexes and the anticonvulsant effect is not sex-specific.

How to use it

Like the Dravet result, this is a prescription use under specialist care with monitoring, and the lower 10 mg/kg dose is often preferred. It is not evidence for retail CBD in ordinary seizure disorders.

The studies · 2

Devinsky et al., Effect of Cannabidiol on Drop Seizures in the Lennox-Gastaut Syndrome · N Engl J Med 2018;378(20):1888-1897

Thiele et al., Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4) · Lancet 2018;391(10125):1085-1096

Prescription CBD cut TSC-associated seizures about 48%, versus 27% on placeboStrong

In plain terms

In a third rare epilepsy, tuberous sclerosis complex, prescription CBD cut seizures by about 48% against about 27% on placebo in a solid trial. It is the third well-established seizure use, alongside Dravet and Lennox-Gastaut syndromes.

In detail

The GWPCARE6 trial added cannabidiol oral solution at 25 or 50 mg/kg/day or placebo to existing antiepileptic drugs in patients aged 1 to 65 with TSC. Both cannabidiol doses reduced seizures significantly more than placebo, with the lower 25 mg/kg/day dose preferred for its better tolerability. The most common adverse effects were diarrhoea and somnolence, more frequent at the higher dose, and elevated liver transaminases occurred in about one in five on cannabidiol and none on placebo. The result supported approval of cannabidiol for TSC-associated seizures.

Who this may not transfer to:The trial enrolled both sexes (about 42% female) and the anticonvulsant effect is not sex-specific.

How to use it

As with the Dravet and Lennox-Gastaut results, this is a prescription use under specialist care with liver monitoring, and the lower 25 mg/kg/day dose is generally preferred. It is not evidence for retail CBD in ordinary seizure disorders.

The study · 1

Thiele et al., Add-on Cannabidiol Treatment for Drug-Resistant Seizures in Tuberous Sclerosis Complex: A Placebo-Controlled Randomized Clinical Trial (GWPCARE6) · JAMA Neurol 2021;78(3):285-292

Anxiety And Stress

A single 300 mg dose of CBD lowered anxiety before a public-speaking test, while 150 and 600 mg did notEmerging

In plain terms

Taking a single moderate dose of CBD before a stressful public-speaking task lowered anxiety in small trials, with around 300 mg working better than higher or lower doses. It is an early, short-term finding about situational anxiety.

In detail

Bergamaschi 2011 gave 24 treatment-naive social anxiety patients 600 mg of cannabidiol or placebo before a simulated public-speaking test and found reduced anxiety, cognitive impairment and discomfort on the active drug. Linares 2019 tested 150, 300 and 600 mg against placebo in 57 healthy men and found only 300 mg significantly reduced anxiety, describing an inverted-U dose-response. These are single-dose, short-term experiments in specific settings, not trials of daily use for an anxiety disorder.

Who this may not transfer to:The primary social-anxiety trial enrolled both sexes; the confirmatory dose-response study was in men only, so the exact optimal dose in women is less certain.

How to use it

The evidence supports a single moderate dose before a specific stressor, not a large daily dose, since more did not help. It should sit alongside established treatment for an anxiety disorder, not replace it, and drug interactions should be checked first.

The studies · 2

Bergamaschi et al., Cannabidiol reduces the anxiety induced by simulated public speaking in treatment-naive social phobia patients · Neuropsychopharmacology 2011;36(6):1219-1226

Linares et al., Cannabidiol presents an inverted U-shaped dose-response curve in a simulated public speaking test · Braz J Psychiatry 2019;41(1):9-14

Pain

CBD on its own did not clearly relieve chronic pain beyond placeboPreliminary · mixed

In plain terms

Despite heavy marketing of CBD for pain, the best current review finds the evidence weak, with any benefit small, and the data on CBD by itself too thin to conclude it reliably relieves chronic pain.

In detail

The review synthesized randomized trials and observational studies of cannabis-based products for chronic pain. Products high in THC showed at most small short-term benefits with meaningful side effects, and the subset of evidence on cannabidiol-only products was sparse, of low certainty, and did not establish a clear analgesic effect. Much of the popular case for CBD in pain rests on preclinical work and testimonials, not controlled human outcomes.

Who this may not transfer to:Pooled across mixed-sex chronic-pain populations; CBD-specific subgroups were too small to assess sex differences.

How to use it

A reader should treat CBD-for-pain claims with caution: the shelf implies reliable relief that the controlled evidence does not support. This is a place where the popular version runs well ahead of the research.

The study · 1

Chou et al., Cannabis-Based Products for Chronic Pain: An Updated Systematic Review · Ann Intern Med 2026;179(2):230-241

Sleep

Sleep scores improved for about two-thirds of adults on CBD in an uncontrolled clinic seriesPreliminary

In plain terms

The main clinical report on CBD and sleep saw sleep scores improve for about two-thirds of people at first, but with no comparison group and gains that came and went. It is too thin to call CBD an established sleep aid.

In detail

Shannon 2019 reviewed charts from a psychiatric clinic where 72 adults received CBD (about 25 to 175 mg/day) alongside usual care, mostly for anxiety or poor sleep. Anxiety scores fell and stayed lower in most patients; sleep scores improved initially in about two-thirds but were more variable month to month. As an open, uncontrolled case series it cannot separate a true CBD effect from placebo, regression to the mean, or the knock-on effect of lower anxiety.

Who this may not transfer to:Both sexes were included in this uncontrolled clinic series; no sex-specific analysis was possible.

How to use it

The durable, free groundwork for sleep does more for most people than a supplement, and CBD-for-sleep should be seen as unconfirmed. If tried, it belongs after the basics and after checking drug interactions.

The study · 1

Shannon et al., Cannabidiol in Anxiety and Sleep: A Large Case Series · Perm J 2019;23:18-041

How It Works

Cannabidiol acts in the brain and in the liver. How far each action carries into an effect you would notice is what separates the strong uses from the marketed ones.

Anatomy of the Practice

1In the brain, in epilepsy

Cannabidiol changes how certain neurons fire, partly through targets other than the usual cannabis receptor, and in these three epilepsies this translates into measurably fewer seizures in controlled trials. This is the only use where the mechanism produces a measured clinical benefit.

2In the stress and fear circuits

At a single dose, cannabidiol dampens activity in brain regions tied to the acute anxiety response. That fits the finding that it blunts the spike of anxiety before a stressful event. The response peaks at a moderate dose and falls off at higher ones.

3In the liver

Cannabidiol is broken down by, and also inhibits, several liver enzymes in the CYP450 family. Those enzymes clear many other drugs, so the same activity can strain the liver and shift the blood levels of medicines taken alongside it.

Using CBD Well

Three things govern whether retail CBD does anything for you: the goal, your medicines, and the product's quality.

If you take an anticoagulant, an anti-seizure drug, or any medicine with a narrow safe range, do not start cannabidiol without checking the interaction with a pharmacist or clinician.

Ways to Do It

Match the goal to the evidence first, sort out your medications, then treat product quality as the main filter. In an unregulated market the label may not match the bottle.

1

Match the goal to the evidence before you buyFreeEasy

The strong evidence is for three rare epilepsies, a medical route. There is early evidence for acute, situational anxiety. For chronic pain and sleep the evidence is weak, so the free basics in the anxiety and insomnia guides are a solid first step.

2

Check your medications firstFreeEasy

Cannabidiol acts on the CYP450 liver enzymes that also clear many common drugs, so before starting anything, list what you take and check it with a pharmacist or clinician. This is free, takes one conversation, and prevents most dangerous interactions.

3

Demand a Certificate of Analysis$ to $$Easy

Labels often miss the real content. Buy only products that publish a recent third-party lab test, a Certificate of Analysis. It should show the actual CBD amount and confirm THC is within legal limits, and it is the one document that verifies what is in the bottle.

4

Understand isolate, broad-spectrum and full-spectrum$ to $$Easy

Isolate is CBD alone. Broad-spectrum adds other hemp compounds but aims to remove THC. Full-spectrum keeps a trace of THC. That is legal below a set limit, but it can still matter for drug testing and for sensitive users. For anyone who must avoid THC entirely, isolate or a THC-free broad-spectrum with a Certificate of Analysis is the safer pick.

5

Know that retail doses run far below the trials$ to $$Easy

The epilepsy trials used 10 to 20 mg per kilogram of body weight a day, hundreds of milligrams for a child. A typical gummy delivers 10 to 25 mg, so a labeled retail dose is a fraction of what the strong evidence tested.

6

For situational anxiety, one moderate dose taken with care$ to $$Easy

The relevant experiment used a single oral dose around 300 mg, taken before a specific stressor. Treat that as short-term and early, keep it alongside proper care for an anxiety disorder, and re-check interactions first.

7

Prescription cannabidiol for specific epilepsies, with a specialist$$$Moderate

The strong seizure evidence is for a prescription product used under a neurologist, for Dravet syndrome, Lennox-Gastaut syndrome or tuberous sclerosis complex. It comes with liver-enzyme monitoring and dose adjustment of any interacting drugs. This is a medical decision made with a specialist, separate from a retail CBD oil.

Go Deeper

• Anxiety: where the early single-dose CBD evidence fits among approaches with a longer track record, and what to build first for an anxiety disorder.
• Insomnia: the durable, free groundwork for sleep, and the practices the evidence supports first.
• Low back pain: a common reason people reach for CBD, and where the controlled pain evidence actually points.
• Interaction checker: test CBD against the prescriptions you take before you start.

The Chinese Medicine View

Chinese medicine has no concept of CBD, and it would be an invention to claim otherwise. The isolated compound does not map onto the tradition. What the tradition holds is a long, cautious relationship with the cannabis plant itself, dosed to the person and the purpose and used sparingly in its potent parts.

The seed, Huo Ma Ren, or fire hemp seed, is a recognized herb. Classed as sweet and neutral, it moistens the intestines and is used gently for dry constipation in the depleted or the elderly. That is a mild, food-like laxative, a different substance from a concentrated cannabinoid extract, and pointing to it does not lend CBD a tradition it lacks. The flowering and resinous parts of the plant were known too, and classical sources treat them warily, warning that in excess they can disturb the spirit and the mind.

Cautions For This Practice

Extra restraint

Everything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.

CBD raised liver enzymes above five times normal in a third of adults at 1,500 mg a day, more so with valproate

Watkins 2021 gave 16 healthy adults a fixed 1,500 mg a day (about 20 mg/kg) for roughly 3.5 weeks; 44% (7 of 16) had ALT above the upper limit of normal and 31% (5 of 16) exceeded five times normal, meeting international drug-induced liver injury criteria and leading to discontinuation, with enzymes recovering on stopping. Dose-dependence comes from the Dravet and Lennox-Gastaut trials, where transaminase elevations were among the more notable adverse effects and concentrated in patients also taking valproate. The signal was strong enough that liver-function monitoring is part of the approved prescribing.Watkins et al., Cannabidiol and Abnormal Liver Chemistries in Healthy Adults: Results of a Phase I Clinical TrialDevinsky et al., Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome

CBD raised the active clobazam metabolite about 500%, forcing dose cuts in most children

Geffrey 2015 prospectively measured clobazam and N-desmethylclobazam levels in 13 children as cannabidiol was added. Levels of the active metabolite rose by a mean of about 500%, roughly five- to sixfold, via CYP2C19 inhibition, and 10 of 13 children had their clobazam dose lowered to manage sedation and other effects, while seizure control generally improved. This is a small, uncontrolled prospective series but a well-characterized, mechanistically expected interaction.Geffrey et al., Drug-drug interaction between clobazam and cannabidiol in children with refractory epilepsy

CBD raised one patient's warfarin effect, requiring about a 30% dose reduction

Grayson 2018 reported a 44-year-old man with post-stroke epilepsy (Marfan syndrome, mechanical mitral valve replacement), stable on warfarin, whose INR rose progressively as cannabidiol was titrated up, necessitating serial warfarin dose reductions of about 30% overall to keep the INR in range. Warfarin is metabolized largely by CYP2C9, which cannabidiol inhibits, making the interaction mechanistically expected. As a single case it is low-tier, but it is a documented, plausible, and clinically important warning for a drug where overshoot causes bleeding.Grayson et al., An interaction between warfarin and cannabidiol, a case report

Liver strain, especially with valproate

Cannabidiol can raise liver-enzyme readings, a sign of strain on the liver. This showed up clearly enough in the epilepsy trials that liver monitoring is built into prescription use. In a phase I trial, healthy adults given a fixed 1,500 mg a day saw liver enzymes climb. About a third rose above five times the normal limit, meeting the criteria for drug-induced liver injury. The risk climbs higher again when cannabidiol is taken with valproate, an epilepsy drug. If you use cannabidiol at any meaningful dose, particularly alongside other medicines, liver-function testing is a reasonable precaution to raise with your clinician.

Drug interactions through CYP450

Cannabidiol inhibits several CYP450 liver enzymes that clear many common drugs, so it can push their blood levels up. A prospective study in children showed it raised the active form of clobazam, an anti-seizure drug, about fivefold, so most of the children needed their clobazam dose cut. A documented case showed it raised the effect of warfarin, a blood thinner, enough to need about a 30% dose reduction. That kept the INR, a measure of blood-thinning, in its safe range. If you take an anticoagulant, an anti-seizure drug, or any medicine with a narrow safe range, do not start cannabidiol without checking the interaction with a pharmacist or clinician.

Label accuracy and THC contamination

The over-the-counter market is poorly regulated. When 84 online CBD products were tested, fewer than a third were labeled accurately for CBD content, and THC was detectable in about one in five. That means an uncertain dose, plus the chance of an unwanted psychoactive compound that can show up on a drug test.

Pregnancy, breastfeeding and children

Outside the specific prescription use for rare epilepsies under a specialist, cannabidiol has not been shown safe in pregnancy or breastfeeding, and regulators advise against it in those situations. Keep retail CBD products away from children, both for the unknowns and because of the THC and dosing uncertainty.

Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.

Common Questions

Does CBD actually work, or is it hype?

It depends entirely on the use, and lumping the uses together is what feeds the hype. The seizure evidence is genuine and strong. Acute, situational anxiety has early single-dose support. For pain and sleep, the evidence is thin and far behind the marketing. So CBD is neither a cure-all nor a scam: it is a compound with a few well-backed uses and many unconfirmed ones.

Is store-bought CBD the same as the prescription kind?

No, and not only in quality. Epidiolex is a specific FDA-approved seizure medicine, dispensed by prescription and taken under a specialist. You cannot buy it on a shelf, and no retail gummy or oil is that product, whatever the label claims. The trials that built CBD's reputation used that pharmaceutical, and no supplement can claim them.

Can CBD interfere with my medications?

Yes, and it is the caution to take most seriously. Bring your full medication list to a pharmacist, and run it through the interaction checker before you start. An anticoagulant or an anti-seizure drug is where it matters most.

What dose of CBD helps with anxiety?

The experiments point to roughly 300 mg taken once, ahead of a one-off stressor such as public speaking. There is no established dose for daily use, or for an anxiety disorder over time, an area with almost no controlled data. If you try it, treat it as short-term, keep real treatment in place, and clear interactions with a pharmacist first.

Does CBD help you sleep?

The evidence is weak and uncontrolled. In one clinic series of 72 adults given CBD mostly for anxiety or sleep, sleep scores improved for about two-thirds in the first month. The improvement was inconsistent from month to month, and there was no comparison group. Much of it tracked falling anxiety, so whether CBD did anything for sleep itself is unclear. The steadier route is the free groundwork in the insomnia guide; if you still try CBD, check the drug interactions before you start.