In the next section, we cover the most common memory issues CBD is known to help with, and back it up with scientific research.
So, have we been misinformed all that time?
CBD for Alzheimer’s and Dementia Memory Loss
But, when you have a high-quality product in your hand, looking for advice on the dosage, here’s one simple advice: start low and go slow.
Studies have shown that the body starts to release endocannabinoids (the body’s version of plant-based cannabinoids) to defend the brain and repair it (3). When phytocannabinoids like CBD are administered to the endocannabinoid system, it strengthens the defensive response, therefore strengthening the memory.
Here’s a summary of the current research:
Whilst the studies in the laboratory show some promise, we need to understand the wider effects that these components have before we can know whether they have any effect – positive or negative – on the development of Alzheimer’s in people.
Products containing more than 0.2% THC are not legally available in the UK.
A few small clinical trials have assessed the effects of cannabinoids (including THC and synthetic cannabinoids, such as nabilone) on behavioural symptoms of dementia. However, trials and studies so far have generally been small or low quality making it difficult to come to a conclusion.
Treating and preventing dementia
Alzheimer’s Society has never funded research into cannabis and dementia risk, or into cannabis as a potential treatment for dementia symptoms.
Cannabis is made up for two main components – Tetrahydrocannabinol and Cannabidiol.
Cannabidiol or CBD does not cause any psychoactive or intoxicating effects.
The jury is still out on whether cannabis or its by-products could be used to treat dementia. A lack of strong research studies mean that dubious and anecdotal reports have taken the place of hard evidence.
The ratio of ∆9-tetrahydrocannabinol (THC) to cannabidiol (CBD) varies widely across cannabis strains. CBD has opposite effects to THC on a variety of cognitive functions, including acute THC-induced memory impairments. However, additional data are needed, especially under naturalistic conditions with higher potency forms of cannabis, commonly available in legal markets. The goal of this study was to collect preliminary data on the acute effects of different THC:CBD ratios on memory testing in a brief verbal recognition task under naturalistic conditions, using legal-market Colorado dispensary products. Thirty-two regular cannabis users consumed cannabis of differing THC and CBD levels purchased from a dispensary and were assessed via blood draw and a verbal recognition memory test both before (pretest) and after (posttest) ad libitum home administration in a mobile laboratory. Memory accuracy decreased as post-use THC blood levels increased (n = 29), whereas performance showed no relationship to CBD blood levels. When controlling for post-use THC blood levels as a covariate, participants using primarily THC-based strains showed significantly worse memory accuracy post-use, whereas subjects using strains containing both THC and CBD showed no differences between pre- and post-use memory performance. Using a brief and sensitive verbal recognition task, our study demonstrated that naturalistic, acute THC use impairs memory in a dose dependent manner, whereas the combination of CBD and THC was not associated with impairment.
Because the recognition task was added onto another ongoing protocol, it was always run after the primary outcome measures for the main study which included assessments of other memory tasks, attention, inhibitory control, balance, and subjective drug effects. These tasks are unlikely to interfere with recognition memory results. The only other verbal memory test included was the International Shopping List Task (ISLT), which used different words than the recognition task. Our larger study found that THC administration was negatively associated with ISLT performance, but CBD results await ongoing data collection and analysis (Bidwell et al. 2020).
Participants (32 cannabis users aged between 21 and 66 years) were recruited from the Boulder-Denver Metro area in Colorado using social media postings and mailed flyers. Because the goal was to collect feasibility data using a novel methodology, the recognition memory task reported here was only assessed in 32 subjects. Trained research staff screened eligible participants via telephone. Criteria for inclusion in the study were: 1) Aged between 21 and 70; 2) Used cannabis at least 4 times in the past month; 3) Experience with the highest potency of cannabis that could be assigned in the study (24% THC for flower groups and 90% THC for concentrate groups); 4) No other non-prescription drug use in the past 60 days; with a urine toxicology screen; 5) No daily tobacco use; 6) Reported drinking 2 times or fewer per week, and ≤ 3 drinks per occasion; 7) Not be pregnant, or trying to become pregnant; 8) No self-reported prior or current psychotic or bipolar disorder. Those eligible for the study completed both a baseline appointment and an experimental appointment, described in greater detail below.
First, we ran a regression model (Eq. 1) to examine how cannabinoid levels (THC + metabolites and CBD) were associated with accuracy (d’). The model revealed that the level of THC + metabolites was significantly negatively correlated to accuracy (p < .05, \( <\eta>_p^2 \) = 0.28) (Fig. 2a), but neither the effect of CBD (Fig. 2b) nor the THC × CBD interaction was significant. This result was observed across the two strain groups, and neither THC nor CBD blood levels were significantly correlated with d′ within each strain group.
Our primary measure of recognition memory performance was d’, but Table 3 shows other performance measures for completeness, including the hit and false alarm rates used to calculate d’. Table 3 shows a measure of response bias (c = − 1/2 * [zH − zFA]), where negative values indicate a liberal bias to respond “old” and positive values indicate a conservative bias to respond “new”. Table 3 also shows response time (RT). Each of these performance measures were separately analyzed in a mixed-design analysis of variance (ANOVA) with session (pretest, posttest) as a within-subject factor, strain group (THC and THC + CBD) as a between-subject factor, and THC + metabolite levels as a covariate.