The first study to suggest that a key cannabis ("marijuana") plant compound, cannabidiol (CBD), can mitigate the interference of Δ9-THC ("THC") with memory formation was lead by Dr. Valerie Curran, PhD, a psychopharmacologist from University College London also studying the effects of cannabis use on creativity at the Beckley Foundation, Oxford, UK.
To test this hypothesis, Curran and her colleagues traveled to the homes of 134 volunteers, where the subjects got high on their own supply before completing a battery of psychological tests designed to measure anxiety, memory recall and other factors such as verbal fluency when both sober and stoned. The researchers then took a portion of the stash back to their laboratory to test how much THC and cannabidiol it contained.
The subjects were divided into groups of high (samples containing more than 0.75% cannabidiol) and low (less than 0.14%) cannabidiol exposure, and the data were filtered so that their THC levels were constant. Analysis showed that participants who had smoked cannabis low in cannabidiol were significantly worse at recalling text than they were when not intoxicated. Those who smoked cannabis high in cannabidiol showed no such impairment.
Ilan attributes the positive finding of Curran and her team to their more powerful methodology in analysing subjects’ own smoking preferences. In the United States, government policy dictates that only marijuana provided by the National Institute on Drug Abuse can be used for research — and it "is notorious for being low in THC and of poor quality", says Ilan.
Lester Grinspoon, professor emeritus of psychiatry at Harvard Medical School in Boston, Massachussetts, who has studied the effects of marijuana on patients since 1967, says that Curran’s study is important."Cannabis with high cannabidiol levels will make a more appealing option for anti-pain, anti-anxiety and anti-spasm treatments, because they can be delivered without causing disconcerting euphoria," he says.
- from "Key ingredient staves off marijuana memory loss," published online, Oct. 1, 2010, Nature. doi:10.1038/news.2010.508
Dr. Curran argues that cannabidiol studies could provide insight into the mechanics of memory formation and reveal therapeutic benefits for disorders involving memory impairments. The research was published October 1, 2010 in the British Journal of Psychiatry ("Impact of cannabidiol on the acute memory and psychotomimetic effects of smoked cannabis: naturalistic study," The British Journal of Psychiatry (2010) 197: 285-290. doi: 10.1192/bjp.bp.110.077503).