For as long as I can remember (see what I did there?), people in my life would say, ‘stay away from marijuana’. Often, the charges against cannabis would be tied in with other ideas such as laziness, poor work ethic, and reduced memory function. As research dollars continue to flow into cannabis, we are finding that several of the key ‘scare’ tactics used were based on outlier evidence and are not totally factual.

In this article, we will discuss some emerging research on how marijuana affects memory. Specifically, we will review how memory is affected by cannabis and hopefully learn once and for all if we may clear the haze from anti-weed tactics and lighten the mood around its use. 

Confronting Old Ideas on Cannabis and Memory

Cannabis use dates back thousands of years, yet its use, cultivation, and sale have been partly-legal for less than half a century. 

Untold thousands have been arrested and several billions of dollars have been collected due to laws around marijuana.

We punish people for using it, for growing it, for having it in their possession, or for selling it. It doesn’t matter the relative devastation caused by cannabis when compared to drugs such as cocaine or an opiate, because drugs are drugs. 

The resulting psychosocial process makes it easier for some individuals with hardline abstinence ideas to be seen as the ‘model’ - the person who stays in favor of the law, of family, and of society. This can magnify small issues to an enormous scale. 

Such is the concept of ‘Reefer Madness’; a rare piece of goofy, anti-drug propaganda, speaking to people as though any use or experimentation with marijuana will leave life unfulfilling and lonely. 

The Problem?

When an experience is awful or conflated, it tends to have an outsized effect on how we recall the experience and our willingness to do it again. As human beings, we all are able to coordinate with others, experience empathy, feel joy and sorrow, and make choices based on information available to us.

As marijuana became more popular in the years leading to the Marihuana Tax Act of 1937, so too did public misunderstandings of the plant. Ideas of madness and paranoia began to percolate around the subject of marijuana, and it was tacked on that significant impairment of memory was from cannabis. 

Back then, the media didn’t move as fast as it does now9 and it was scientifically valid to blame mothers for schizophrenia. Times have changed.

With more and more states legalizing cannabis after 80 years of prohibition, it is time to employ some of the advances in technological and scientific understanding to gain perspective. 

True: memory and reaction time are statistically correlated to cannabis use.

False: memory retrieval gets worse with cannabis use.

What is Working Memory?

Working memory is a lot like the RAM memory of a computer. It does not mean the information has been hard-coded into our memory. Instead, working memory implies a near-term function, where maybe only seconds to days have passed. 

On the topic of working memory and cannabis use, one recent study sticks out in particular. The study observed 75 participants, 60 of which have used cannabis while 15 had not. The objective was to determine whether the age of onset - that is, when in an individual’s life they first used cannabis - is related to working memory reaction time in the near-term.

Working memory reaction time was measured using a system of cues and responses which imitated the typical functioning of memory in our environment. With regard to memory and cannabis use, the series of cues made by researchers additionally evaluated the following:

• Memory Encoding: This was evaluated by showing one or three stimuli to be recollected.

• Memory Maintenance: Using advanced imaging technology (fMRI), memory maintenance was evaluated by showing where the information was held and maintained in the brain. 

• Memory retrieval: This was measured by showing four stimuli and evaluated by matching cues to the previous stimuli.

As the main focus of the study was to determine if the reaction time of an individual’s working memory relates to cannabis use IF exposed during adolescence, the true results of the study provide evidence that cannabis and memory have a highly variable, if not totally illogical, relationship. 

So How Does Marijuana Affect Memory?

By using an fMRI scanner, researchers were able to show the parts of the brain which are most active when supplied with the encoding, maintenance, and retrieval stimuli. 

As was consistent with previous research, the areas of the brain researchers focused on include the posterior parietal cortex (PPC) and dorsolateral prefrontal cortex (DLPFC), which help regulate executive function and control in the near-term. 

The results found three relationships regarding working memory and cannabis use worth noting. 

First and most, unfortunately, the research reinforced the idea that individuals who began using cannabis earlier in life had longer reaction times than both cannabis users who began using after adolescence and non-users. This suggests broadly that cannabis use may impact the development of encoding information if used early in life. 

(Note: this does not mean cannabis use is a predictive factor for memory issues, rather working memory and cannabis use may have a relationship.)

Second, the age an individual first uses cannabis and whether they have used cannabis once or repeatedly had no relationship to the behavior of the brain. 

According to researchers, this may suggest the age a person initially uses cannabis may reflect substance use risk characteristics rather than a cannabis-exposure effect (such as impaired memory) on brain development. 

And last but not least, among the group of 75 participants, the researchers were able to show repeated cannabis use AND greater levels of overall cannabis use were associated with increases of performance in the activation (i.e. - working of) of the dorsolateral prefrontal cortex (DLPFC) during the maintenance period.

Additionally, across all 75 participants, users of cannabis generally performed better than non-users, which includes a faster reaction time and higher memory retrieval accuracy.

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