Does Cannabis Impair Cognitive Functioning? What The Research ACTUALLY Says…

Lieze Boshoff | LBC3 Marketing
4 min readFeb 20, 2018


Every so often the cannabis-makes-you-stupid type headline (like this one in the Daily Mail) pops up in the main stream media, citing the latest “definitive” study showing that cannabis impairs memory and cognitive function… Others, like this Times article cites a different source which conclusively shows “no”, cannabis is quite safe to use and does NOT impair cognitive functioning after all.

So, which is it then? Why all the confusion? Does cannabis really impair memory and cognitive functioning?

Let’s look at what the research really says…


Because cannabis is still largely illegal, studying it and getting the results published can get quite sticky. The field of cannabis research is fraught with issues, ranging from the lack of a standard set of research methodologies, to recruitment protocols resulting in non-representative samples (they mostly draw from a pool of drug treatment centres or doctors’ referrals — read more about the nitty gritty of cannabis research in the behavioural sciences here).

These issues are in and of themselves problematic because conclusions are drawn based on:

  • post-hoc analyses where contributing factors are not controlled or accounted for…
  • on data from non-representative patient populations…
  • that are being treated for psychological and/or other substance abuse/addiction issues.

And it is longitudinal studies especially that employ these types of methodologies… The study cited in the Daily Mail article above is a prime example — especially note the subtle inclusion of alcohol, murkying the results of that particular study.

Another issue is that the funding bodies and institutes behind these types of studies are not always entirely objective. Often times there is an “agenda” behind the study — either wanting to support/reject political and health policies, or either support/refute certain hypotheses and findings — that can lead to researcher bias.

In a similar vein, in some cases results that contradict the latest en vogue hypotheses are sometimes minimised, other times ignored, and often times left unreported and unpublished (academic publications are all about “statistically significant results” and “hypothesis confirmations”).

But, the most important issue is this…

The standard method for cannabis research in quantitative brain and behavioural studies is to group all types of cannabis into one big sample and collectively study the effects of cannabis on users (National Academies of Sciences, 2017).

Essentially, cannabis researchers are drawing conclusion about cannabis, its effects, side-effects and associated dangers without studying the individual cannabis compounds and their individual effects…

Think of it as being akin to researchers doing a study on the effect of painkillers, chucking paracetamol, ibuprofen and opioids into one big heap, giving it to users, study the effects, and coming to the conclusion that all painkillers have the same effects, side-effects and dangers.

Which bring us to the second issue…


We know that the THC affects the brain, cognition and behaviour differently than CBDs do. So too do things like potency, the concentrations of active ingredients and delivery method. Super important but rarely controlled for.

Different strains have different active ingredients each with differing ratios and at different concentrations. The constituents of hash are different to those found in unprocessed flower buds or cannabis resin. Whether cannabis is smoked, ingested orally, or applied topically also has a huge impact on the associated effects of its use.

Even more importantly, we know that THC and CBDs display opposing neural, cognitive, and behavioural effects. For instance, this 2017 study shows that THC has a detrimental impact on memory and emotional processing while CBD might actually improve memory and cognition.

Further evidence from other clinical studies also indicate that THC impairs learning and working memory 1, 2, 3 while CBD not only enhances learning and memory it actually counteracts the negative effects induced by THC 1, 2, 3.

At a minimum, these findings highlight an urgent need isolate and investigate each cannabis compound on an individual basis, especially when it comes to THC versus CBD.

And without doing this, along with actually measuring and standardising potency and the concentrations of active ingredients of cannabis samples used in studies, and accounting for delivery methods, it is very difficult to draw clear, objective and robust conclusions about the impact of cannabis on cognitive function and other health related issues.


When reading these “The terrible truth about cannabis” type headlines, it is easy to have a knee-jerk reaction. For some it is easy to reject the information as fear mongering and anti-cannabis propaganda. For others it is more comfortable to view them as confirmation that cannabis is indeed a dangerous, highly addictive drug that makes people stupid.

The truth however is that cannabis contains more than 80 different cannabinoid compounds which includes a myriad of CBDs, terpenes and THCs — each affecting brain functioning and behaviours in a different way.

So, does cannabis make you stupid? It would seem that a lot more objective research needs to be done, that isolates compounds, use robust research protocols on representative population samples, before any results can be considered as being “definitive”.


Lieze, is the founder of LBC3 Marketing, a leading content marketing and copywriting consultancy, working exclusively in the cannabis industry.

Using everything she’s learned over the years, she use a unique blend of psychological profiling techniques, tried-and-true content marketing and copywriting strategies, as well as Medical Cannabis and CBD industry experience, to help her clients get strategic about their Content Marketing and Copywriting.

If you’re ready to see the impact a strategic Content Marketing plan and well-crafted Copywriting can do for you and your cannabis business, take that first step, contact her here for a free consultation.



Lieze Boshoff | LBC3 Marketing

Lieze Boshoff (B.Psych, M.SC (HCN)) is the founder of LBC3 Marketing, a content marketing agency with 5+ years of exclusive Cannabis | CBD industry experience