Highly variable; in epilepsy, high doses are used by prescription. Quality and labeling are very uneven on the market.
Older clinical trials: CBD doses (up to 600 mg) showed no toxicity or psychotropic effects, but several volunteers reported drowsiness, and hypnotic (sleep) and antiepileptic effects were observed. Small, old studies; consistent with current uses of CBD.
View the study (study) →⏱ 4 min read
Cannabidiol, or CBD, is one of more than 100 cannabinoids identified in the Cannabis sativa plant, along with tetrahydrocannabinol (THC), which is the main one responsible for the psychoactive effects of recreational cannabis; unlike THC, CBD does not produce intoxication and is not psychoactive in the recreational sense, and it has a distinct pharmacological profile that combines effects on the endogenous endocannabinoid system, on serotonin receptors, on TRPV1 channels, and on multiple other molecular targets with clinical relevance in anxiety, chronic pain, sleep, inflammation, and, especially, in some refractory epileptic conditions where pharmaceutical CBD is already a first-line treatment.
The regulatory status of CBD is complex and varies internationally: in some countries it is fully legal as a supplement or functional food, in others it is restricted to medical use with a specific prescription, and in others it remains prohibited or in legal gray areas; in Spain, CBD can be marketed as a cosmetic (not for consumption) and as a specific authorized medicine (Epidyolex for some forms of refractory epilepsy); products sold as "CBD oils for oral use" are in an ambiguous regulatory zone that is worth understanding before use.
The indication with the most robust clinical support, sufficient for authorization as a medicine, is the treatment of specific refractory epilepsies in childhood: Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex; several placebo-controlled randomized trials have shown 30–50 percent reductions in seizure frequency in patients with epilepsies previously refractory to multiple antiepileptic drugs, a clinically notable efficacy that led to the regulatory approval of Epidyolex (purified pharmaceutical cannabidiol) by the FDA and the EMA.
In anxiety, several small trials and a growing body of evidence have documented significant improvements in social anxiety, post-traumatic stress disorder, generalized anxiety, and anticipatory anxiety with doses of 25–600 mg/day over weeks to months; the effects are usually faster than with SSRIs and with a different tolerability profile, positioning CBD as an emerging option in anxiolysis, although the methodological quality of the studies is heterogeneous and the evidence continues to grow.
In chronic pain (especially neuropathic and musculoskeletal), several trials have documented modest improvements on pain scales with doses of 100–600 mg/day; the effects are quantitatively smaller than those of opioids or other specific pharmacological interventions but may be clinically useful as an adjunct, with a favorable tolerability profile and no risk of dependence.
In insomnia, especially when associated with anxiety or chronic pain, CBD at moderate doses (25–160 mg) taken in the late afternoon or evening may improve sleep onset and quality in small studies; the effects are heterogeneous depending on the underlying condition and the doses used, with magnitudes that are generally modest but clinically useful for some patients.
The market for unregulated CBD products is a real clinical problem: several independent studies have documented that a significant proportion of commercial CBD products (especially oils and edibles) have an actual CBD content significantly different from the one stated on the label (sometimes much lower, sometimes much higher, occasionally zero); in addition, a non-negligible proportion contain undeclared residual THC in amounts sufficient to produce psychoactive effects or problems in anti-doping tests; it is advisable to choose products with independent certification of content and third-party purity verification (a Certificate of Analysis, or accessible COA).
The doses studied vary enormously depending on the indication: for pharmaceutical refractory epilepsy, 5–20 mg/kg/day divided; for anxiety and pain, 25–600 mg/day with gradual escalation; for sleep, 25–160 mg in a single evening dose; CBD has modest oral bioavailability (10–20 percent), better with a fatty meal; sublingual oils have higher bioavailability through mucosal absorption; pharmaceutical products have regulated purity and dosing, while commercial ones can be very heterogeneous.
Generally well tolerated at the doses studied; the most frequent adverse effects are drowsiness, fatigue, diarrhea, appetite changes, and weight changes; CBD is a potent inhibitor of several hepatic cytochrome P450 enzymes (especially CYP3A4 and CYP2C19), with clinically relevant drug interactions that include warfarin, clobazam, valproate (where it increases the risk of hepatotoxicity), tacrolimus, sirolimus, some antidepressants, and many other drugs metabolized through these pathways; people with substantial polypharmacy should consult their doctor beforehand; CBD can transiently raise liver transaminases, especially in combination with other hepatotoxic drugs; in pregnancy and breastfeeding it is not recommended because of limited data; products with undeclared residual THC can produce positive anti-doping test results and legal problems in jurisdictions with restrictive regulation; professionals with specific responsibilities (professional driving, safety-sensitive jobs) should consider the legal and professional implications before starting; high doses or prolonged use should be under medical supervision, especially if there is polypharmacy or liver disease.
Information, not medical advice. Scientific evidence reflects the quality of the studies.