Journal of Psychopharmacology
October 5, 2012
Amir Englund, Paul D. Morrison, Judith Nottage et al.
463 citations
Pre-treatment with 600 mg of cannabidiol (CBD) reduced the likelihood of clinically significant psychotic symptoms and paranoia caused by intravenous delta-9-tetrahydrocannabinol (THC, 1.5 mg) in healthy volunteers. Participants who received CBD before THC had lower scores on the State Social Paranoia Scale and smaller declines in episodic memory compared with those who received placebo before THC. The odds of experiencing a clinically significant increase in positive psychotic symptoms were about 78% lower in the CBD group. These results support the view that cannabis products high in THC and low in CBD pose greater mental health risks.
Addiction
February 8, 2023
Will Lawn, Katie Trinci, Claire Mokrysz et al.
36 citations
Adolescent cannabis users are neither more resilient nor more vulnerable than adult cannabis users to the acute psychotomimetic, verbal memory-impairing, or subjective effects of cannabis. In a randomized, double-blind, placebo-controlled crossover experiment with 24 adolescents (16-17 years old) and 24 adults (26-29 years old) who used cannabis 0.5-3 days per week, vaporized THC (8 mg for a 75 kg person) and THC plus CBD (24 mg) both significantly increased subjective drug effect, impaired verbal episodic memory, and increased psychotomimetic effects compared to placebo. There was no evidence that adolescents differed from adults in their responses, and CBD did not modulate the acute effects of THC.
Cannabis and Cannabinoid Research
December 9, 2022
Lucy Chester, Amir Englund, Edward Chesney et al.
20 citations
Inhaling vaporized cannabis containing 10 mg of THC acutely increased blood levels of the endocannabinoid anandamide by 18% and several related noncannabinoid lipids, but adding 10, 20, or 30 mg of CBD did not alter these effects. Over four sessions spaced about two weeks apart, pre-inhalation levels of anandamide and one related compound progressively declined, possibly due to repeated THC exposure or reduced anxiety. The findings suggest that CBD, at the doses tested, does not modulate THC's acute influence on endocannabinoid concentrations, though higher or chronic CBD doses might have an effect.
Neuroscience and Biobehavioral Reviews
September 1, 2026
Isabella Goodwin, Dominic Oliver, Edward Chesney et al.
A meta-analysis of 41 double-blind, placebo-controlled experiments involving 1,020 infrequent cannabis users found that acute THC administration increases feelings of high, anxiety, and tiredness, while decreasing alertness and contentedness, with no effect on calmness. Inhaled THC dose-dependently increased high and contentedness but decreased calmness, with greater consistency in high and contentedness at higher doses. On a 100-point scale, inhaling 5 mg THC increased high by 34.3 points, anxiety by 14.4, tiredness by 26.3, and calmness by 4.5, while decreasing alertness by 40.2 and contentedness by 71.0. Oral THC showed no significant subjective effects, though higher oral doses produced more consistent alertness. These findings can inform public health guidance on expected THC effects.
Frontiers in Psychiatry
January 1, 2024
Xinyi Liang, Maria-Mihaela Avram, Toni Gibbs-Dean et al.
Regular cannabis users show no overall difference from non-users in how they update their beliefs under uncertainty, a cognitive process linked to psychosis. Both groups correctly adjusted their confidence and learning when uncertainty changed. However, among cannabis users, those who used cannabis more frequently performed worse on the task than less frequent users. This pattern resembles the abnormal belief-updating seen in psychosis, suggesting that frequent cannabis use may share a cognitive risk marker with psychosis, even though cannabis use status alone does not impair this process.