Benefits
Calm under acute stress
In small double-blind studies, a single 600 mg dose lowered anxiety during a public speaking test in 24 people with social anxiety, and 300 mg (but not 150 or 600 mg) did so in healthy men. A 4-week study of 300 mg a day in 37 teenagers with social anxiety reported lower anxiety scores. Adding 300 mg to exposure therapy did not improve outcomes.
Sleep quality
In a 2-week randomized trial of 150 mg nightly in 30 adults with insomnia, insomnia severity, time to fall asleep and time awake at night did not differ from placebo, though well-being and one objective sleep efficiency measure were better. A clinic case series without a control group reported sleep scores that improved early but fluctuated over time.
Mood and emotional well-being
A large review of cannabinoids for mental health found scarce evidence that they improve depression or anxiety disorders, with few trials of CBD alone. In women with advanced breast cancer, a single 400 mg dose missed its main anxiety endpoint, though anxiety was lower 2 to 4 hours after the dose.
Mechanism of action
Endocannabinoid system
CBD is described as inhibiting the breakdown of anandamide, one of the body's own cannabinoids, which may raise endocannabinoid signaling. In an exposure therapy trial built on this idea, CBD did not improve outcomes.
Bell-shaped dose response
In a public speaking study, 300 mg of CBD reduced anxiety while 150 mg and 600 mg did not, matching the bell-shaped dose curves reported in animal studies. A higher dose is not necessarily more calming.
Liver metabolism and drug interactions
CBD is broken down by liver cytochrome P450 enzymes and can raise blood levels of other drugs handled by the same enzymes, such as clobazam. At higher doses it can raise liver enzymes.
Clinical trials
Double-blind randomized study of a single 600 mg oral dose of CBD or placebo 90 minutes before a simulated public speaking test (Bergamaschi et al. 2011, Neuropsychopharmacology)
24 treatment-naive people with generalized social anxiety disorder, plus 12 healthy controls without treatment
CBD significantly reduced anxiety, cognitive impairment and discomfort during the speech compared with placebo, bringing responses close to the healthy controls. One dose, small sample.
Double-blind study of single oral doses of CBD 150 mg, 300 mg or 600 mg versus placebo before a simulated public speaking test (Linares et al. 2019, Braz J Psychiatry)
57 healthy men
Only 300 mg reduced anxiety during the speech compared with placebo; 150 mg and 600 mg did not differ from placebo, an inverted U-shaped dose response.
Double-blind study of cannabis oil containing 300 mg CBD or placebo daily for 4 weeks (Masataka 2019, Front Psychol)
37 Japanese 18 to 19 year olds with social anxiety disorder and avoidant personality disorder
CBD significantly lowered scores on the Fear of Negative Evaluation Questionnaire and the Liebowitz Social Anxiety Scale. Small, single-author study.
Double-blind randomized controlled trial of 300 mg oral CBD or placebo given with each of eight weekly exposure therapy sessions (Kwee et al. 2022, Eur Neuropsychopharmacol)
80 treatment-refractory patients with social anxiety disorder or panic disorder with agoraphobia
No difference between CBD and placebo in fear questionnaire scores over time, through 6 months of follow-up. CBD did not speed early response or improve fear extinction. Adverse effects were similar.
Phase II double-masked, placebo-controlled randomized trial of a single 400 mg oral dose of CBD within 48 hours before a cancer scan (Nayak et al. 2024, JAMA Netw Open)
50 women with advanced breast cancer and clinical anxiety
The primary endpoint, change in the afraid subscale before versus after the dose, did not differ between groups (P = .37). A secondary comparison found lower afraid scores 2 to 4 hours after CBD than placebo (P = .02). No grade 3 or 4 toxic effects.
Randomized, placebo-controlled pilot trial: placebo run-in week, then 2 weeks of 150 mg CBD or placebo taken under the tongue 60 minutes before bed (Narayan et al. 2024, J Clin Sleep Med)
30 adults with moderate to severe primary insomnia
Insomnia severity, self-reported sleep onset latency, sleep efficiency and wake after sleep onset did not differ from placebo. The CBD group had higher well-being scores and better objective sleep efficiency at week 2.
Randomized, double-blind, placebo-controlled trial of oral CBD 600 mg/day or placebo for 8 weeks added to paracetamol 3 g/day (Pramhas et al. 2023, Lancet Reg Health Eur)
86 adults with painful knee osteoarthritis
Pain fell by 2.5 points with CBD and 2.4 with placebo, with no significant difference (p = 0.80). Adverse events and rises in liver enzymes were more common with CBD.
Randomized, double-blind, placebo-controlled trial of CBD 5 mg/kg/day (2.5 mg/kg twice daily) or placebo for 28 days (Florian et al. 2025, JAMA Intern Med)
201 healthy adults
8 people taking CBD (5.6%) and none on placebo had liver enzyme rises above 3 times the upper limit of normal; 7 met withdrawal criteria for possible drug-induced liver injury. Testosterone, inhibin B and thyroid hormones did not change versus placebo.