A new study has said that some particular forms of cannabis may contain an ingredient that helps to diminish the drug's negative effects on memory.
The new study has revealed that the strain of cannabis makes all the difference, reports Nature.
In a test of short-term memory skills, only users of 'skunk'-type strains exhibited impaired recall when intoxicated, whereas people who smoked hashish or herbal cannabis blends performed equally well whether they were stoned or sober.
The findings suggest that an ingredient more plentiful in some types of marijuana than in others may help to reduce the memory loss that some users suffer.
The key difference between the types of cannabis is the ratio of two chemicals found in all strains. Tetrahydrocannabinol (THC) is the primary active ingredient and the second chemical, cannabidiol.
Valerie Curran of the University College London who led the latest study, said that if habitual users must partake they should be encouraged to use strains with higher levels of cannabidiol, rather than using skunk.
Researchers had been suspecting that any effects of the drug on mental health could be a result of an increased ratio of THC to cannabidiol in cannabis, because levels of cannabidiol have not kept pace with rising THC concentrations.
To test this hypothesis, Curran and her colleagues travelled 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 percent cannabidiol) and low (less than 0.14 percent) 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.
The results suggested that cannabidiol could mitigate THC's interference with memory formation.
The findings are published in the British Journal of Psychiatry today.