Effects of different methods of cannabis use on cognition and blood THC: A systematic review

Novel methods of cannabis use are becoming popular, but the differential impact of these new methods on cognition have not been widely studied. Further, the impact of cannabis on cognition is mediated by delta-9-tetrahydrocannabinol (THC), but few studies have directly compared the pharmacokinetics of different methods. This systematic review (PROSPERO, CRD42023442731) was conducted to determine whether the different forms of cannabis and routes of administration have differential acute effects on cognition or blood THC. In total, six studies were found that directly compared the effects of at least two different methods of cannabis administration on cognition and eight studies compared the impact of different methods on blood THC. In general, few differences between methods were found on cognitive performance but two studies found some evidence for worse performance on attention tasks after vaping cannabis versus edibles or smoked cannabis. One study found worse performance on a memory task in participants who smoked high potency flower with cannabidiol compared to a group of concentrates users. Despite this, the clear consensus is that inhaled routes of administration result in higher peak levels of THC, while edible cannabis has a longer duration of action. Additionally, one study found an inverse correlation between blood THC and cognition. Given that THC levels are used to detect impairment, this suggests that the ability to detect impairment may vary by method, with edibles presenting more of a challenge. More studies are needed to understand the effects of these newer methods of cannabis administration on performance and blood THC.