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How Does Cannabis Affect Your Memory?

June 14, 2016

Dude, where’s my car? Cheech & Chong. Jeff Spicoli. Harold & Kumar. Popular culture is littered with references to lovable—yet, usually forgetful—“stoners.” Cannabis and poor memory seem to go hand in hand, right? But, what does the science really say about cannabis and its effect on the ability to remember?

To better understand how cannabis affects memory, it’s important to first recognize that memory is not a construct that can be easily measured. Why? There are many different types of memory, each of which we test in different ways. Secondly, there are acute, or short-term, effects on memory (e.g., while under the influence), and possible long-term effects. And, finally, dosing, frequency, and strains play a big role in how cannabis affects memory.

What Are the Short-Term Effects of Cannabis on Memory?

Reminder string tied around a finger

THC, the primary constituent in cannabis that gives users a euphoric effect, appears to impair memory in two significant ways:

  1. Difficulty encoding memories: While cannabis users don’t experience “blackouts” like drinkers do after a big binge, it’s more difficult to form new memories while under the influence.
  2. Short-term recall difficulties: Recalling events while high, and often for a period after the high wears off, can be a challenge.

Interestingly, studies show that frequent cannabis users may develop a tolerance to these effects. In other words, they become less sensitive to these effects and have less difficulty encoding memories or recalling events after use.

The good news is that in most consumers, memory impairments appear to be temporary. One study found that THC significantly impaired recall two hours after consumption, but no residual effects persisted after 24 to 48 hours. Also, cannabis doesn’t appear to affect one’s ability to recall existing memories. For example, even if you’re really stoned, you’re unlikely to forget your birth date, where you live, or what school you graduated from.

What Are the Long-Term Effects of Cannabis on Memory?

Holding up a blank photograph

Higher doses of cannabis taken frequently can have an adverse effect on long-term memory. In one study published by JAMA Internal Medicine, researchers concluded that people who consume a lot of cannabis over a long period of time (five or more years) developed poorer verbal memory recall than people who consumed less or not at all.

But how much was their memory impacted?

Reto Auer, a professor at the University of Lausanne in Switzerland and the study’s main author, said they looked at nearly 3,400 Americans over a 25-year period. Testing verbal recall, they found that users who smoked every day could, on average, recall 8.5 out of every 15 words. In contrast, those who smoked much less or didn’t consume at all could recall 9 out of every 15 words.


The Medical Minute: Paranoia, Memory, and the Gateway Drug Theory

While the difference of half a word doesn’t seem like much, Auer suggested that the longer one consumed chronically, the worse their memory might get. But, of those who participated in the study, only 8 percent considered themselves frequent users.

Notably, they didn’t find that heavy users had other adversely impacted cognitive abilities, such as focus and processing speed.

Can Cannabis Protect Memory?

Locked wooden doors

Some studies suggest that higher levels of CBD – a non-intoxicating cannabis constituent – may offset THC’s memory impairment. Better yet, CBD may have therapeutic potential to reverse or prevent certain cognitive impairments.

Early research shows that CBD could protect against brain damage caused by binge drinking or alcohol abuse. The National Institute of Mental Health (NIMH) reported that CBD reduced alcohol-induced cell death in the brain by up to 60 percent.

Other studies have shown that CBD could act as a neuroprotectant and help prevent the onset of diseases like Parkinson’s, dementia, or Alzheimer’s.


5 Ways Cannabis Could Be Helping Alzheimer’s Patients

Cannabis May Help Fight Bad Memories

Depressed, upset woman

Generally, we don’t think of memory impairment as a good thing. However, when it comes to individuals with PTSD, it’s a different story. One of PTSD’s defining symptoms is the inability of sufferers to extinguish memories from the traumatic event (or events) that caused the PTSD such as abuse, sexual assault, or combat.

Veterans regularly complain that pharmaceutical treatments prescribed to them by doctors – such as the highly addictive anti-anxiety medications Xanax and Valium – don’t work well and sometimes worsen symptoms.

Many veterans turn to cannabis claiming it’s the only thing that works; preclinical research shows that THC and CBD can “disrupt the reconsolidation of negative memories.” Translation: as Dr. Mike Hart from Marijuana for Trauma explains, “Cannabis helps people forget painful and intrusive memories.”


Cannabis and Post-Traumatic Stress Disorder (PTSD)

Further Research Is Needed

Scientific research

We’re just beginning to understand how cannabis use affects the brain and memory, but encouragingly, it seems the adverse effects are exaggerated. Yes, cannabis can make you forgetful while using (or shortly thereafter). And, yes, it can have a modest impact on verbal recall in chronic, long-term users. But, in most people, after a short period of abstinence, memory function returns to normal.

Moreover, we are discovering potential therapeutic benefits. Of course, the old cop-out rings true: further research is needed, especially when it comes to studying cannabis to treat disorders like PTSD, or to prevent conditions such as Alzheimer’s, Parkinson’s, and dementia that affect millions of people. However, we can hope that as public opinion shifts, the federal government will follow suit and ease restrictions that enable scientists to take research out of the lab and conduct more clinical studies on human subjects.

  • Franklin

    How can we believe any of this research when it is brought to us by the same people who propagate reefer madness for a living? When a human is highly focused, or in a deep state of medication, memory recall about other subject will be clearly impaired. Any claim that was made about marijuana even 40 years ago, was negative, and was the figment of an imagination. There were no studies.

    So we have to question anything that is now backed up by a study of data from another research project. It is possible to skew data in any direction you want. We see new studies released by a SAM affiliate every month, and if you look last year, they were the same topics. Then we can see that the DEA didn’t approve any new studies on the subject.

    This story came out of the UK Daily Mail which is like the National Inquirer. Elvis is usually spotted somewhere with Big Foot. One of the studies they reported last year from a “doctor” on psychosis was the thesis of a Polish medical student. SAM published it through the Medscape group of websites. MedExpress. Science Daily, etc. It gets mistaken for real news. Every pillow and flashlight on TV is cliinically proven, laboratory tested and doctor approved. It means nothing anymore. There are only a few hundred thousand doctors affiliated with Harvard for example. SAM pays for a report on old data each for each month.

    Right now they are recycling the lazy old Chong myth, Next month is will be psychosis or association with violence, Not one of these claimes is new. The last new prohibition shenanigan was, the one telling people that they had really crappy ditch weed at Woodstock. Aside from that this is just a repeat of everything that was attached the prohibition of intoxicating beverages. The blanket claims covered everything that they wanted to ban. They have dropped the claim of rickets and the uncontrollable desire to sleep with Jazz musicians. They have made PC changes in language but nothing else.

    We can have a discussion about the potential harm of the plant if any, after the guns are put away. It’s easy to forget out here that back on the East Coast the drug war is still fully funded. They still kicking in doors every night with their black masks on terrorizing families. You cannot have a reasonable discussion with the propaganda arm of that same band of monsters. They are doing all of this for profit and power and no other reason. As far as I’m concerned there is no proven harm or even impairment from the cannabis plant.

    • Charis Isis Kroeker

      Thank you! Completely and 100% agree with you about this and I am such there are hundreds of millions of people who feel the same way, thank you for speaking for all of us!

    • gamergirl86

      Thank you for your comment! When reading the article myself, it did occur to me that some of these “research studies” held various claims that otherwise proved inconclusive. For example, when the article stated: ” those who participated in the study,

      “only 8 percent considered themselves frequent users.”

      Considered? What were the ages of these participants? How is “frequent” defined in each category? How long did this “Research” go on for and what was the size of the sample?

      This is what I am longing to read about in a medical journal article and I cannot find anything. As far as I’m concerned, I agree that there is no impairment from marijuana.

      • Franklin

        Self reporting questionnaires are usually taken with a grain of salt in the science community. There might still be interesting data there but any result, positive or negative is predetermined. If we are only looking for a negative, then the report will be negative.

        There is only one gold standard study in the United States and that data is the basis for all genuine research. Dr. Donald Tashkin still leads the only genuine study on smoked marijuana approved by the NIH, DEA, and FDA. Commissioned by the NIH to fist compare the effects of smoking tobacco and smoking marijuana.

        To their surprised Dr. Tashkin discovered that marijuana smoke doesn’t affect the lungs at all like tobacco. Final conclusion is that marijuana smoking does has “zero” connection to cancer of the lung, neck, or throat. The study is ongoing with reporting questionaries, but it is the same test group of people still being followed who participated in the first actual study. None of the test subjects who smoke marijuana had developed lung cancers, although some who were tobacco smokers did and some non smoker of anything developed lung cancer. That suggests a protective effect.

        Nearly all genuine studies use data from the Taskin studies at UCLA because it is the only solid data available. They simply change the positive outcomes to negative and vice versa. We will know for certain if any harm is ever proven for the marijuana plant. The CDC will call a press conference because so many American consume marijuana. About 40 million admit to trying it and that can’t include any military or DOD contractors because it’s against contract. It won’t appear in the UK Daily Mail or Science Daily website sponsored by beet juice.

  • lovingc


    • joeythepug

      Can’t argue when you’re wright! And Sir YOUR 100%WRIGHT!

  • Mary Lucas

    One of the biggest myths about cannabis is that it’s bad for the brain. Agreeing to this is just perpetuating the stupid stoner stereotype. If we want to push for legalization, we must crush this myth! Everything here is true!

  • disqus_etaC7NTHiO

    I agree with this almost completely my husband’s memory is so bad and it’s so frustrating because you can’t be open with him and tell him how you feel.

  • Guillermo Alvarado

    There are no long term effects on memory from cannabis use. I have been a “stoner” since high school and am now 35. I can clearly remember everything since, read at a 1,000 words a minute with a 90% percent recall. In other words I can read most of these comments in less then a minute and then repeat them to you almost word for word. My favorite thing to do when I’m high is to curl up with a good sci-fi or fantasy novel. If I’m high enough I stop seeing words and instead a sort of super detailed movie plays in my head. Maybe it’s just me, but I feel that there are no real adverse effects to memory.

  • viper643

    Forgot what the question was.

  • Randall Burns

    I would like to see the effect of cannabis differentiated from the effects of smoking. Those that use a high quality vaporizer are not ingesting CO, which has all kinds of potentially negative effects.