4. Can we make cannabis safer? An experimental study of four CBD: THC rations in healthy volunteers

Pharmacological investigations of CBD and THC have found these two cannabinoids to be vastly different in terms of mechanism of action and some studies have found CBD may offset some of the negative impact of THC. It has been suggested that the addition of CBD to cannabis may reduce the harms of cannabis use and some retailers are marketing CBD-containing cannabis in this way. Here we investigate the different effects of the four CBD:THC ratios most commonly available on legal recreational markets.

Healthy volunteers (N=46) attended 5 study visits, 1 baseline and 4 experimental drug administration visits. On each visits participant were administered 10mg intrapulmonary THC, coadministered with either 0mg, 10mg, 20mg, 30mg CBD (CBD:THC ratios – 0:1, 1:1, 2:1 and 3:1). Standardised assessments were used to study changes to cognitive performance, psychopathology, subjective effects, physiological, as well as pharmacokinetic data.

THC alone reliably produced cognitive impairment, psychotic-like symptoms, and subjective effects compared to baseline. There were no significant differences between THC alone and any of the CBD-ratios on these outcomes. Analysis of subjective effects found a dose-response relationship whereby a higher CBD:THC ratio exacerbated subjective effects. Significant paranoia was only observed for the 1:1 and 2:1 CBD:THC ratios.

The most commonly available CBD:THC ratios on legal recreational markets offer no protection compared to THC alone (when THC dose remains constant) on cognitive, psychopathological or subjective outcomes.