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Guide to Marijuana & Memory Effects (Loss & More)

For decades, small studies here and there have demonstrated the negative impact that marijuana use has on some people.

With increased access to legal marijuana, it has become easier for scientists to research the effects of the drug at different doses, among varying populations, and in combination with other substances. To formally document the how and why of marijuana addiction development, federal agencies have also been investigating the drug, and the research is mounting.

Not only is marijuana much more addictive than formerly thought, but it can also significantly harm cognitive function, including causing memory impairment.


The short answer is yes. In a study of almost 4,000 young adults tracked over 25 years until mid-adulthood, lower scores on verbal memory testing were associated with cumulative lifetime exposure to marijuana. This impact was sizeable and remained a statistically significant problem even when the study adjusted for other factors, such as co-occurring disorders, addiction, and demographics.

Another study showed that nonverbal memory testing ability fell among participants due to marijuana use.

Yet another large study in New Zealand found that frequent marijuana use that started during adolescence was correlated with an average loss of between 6 and 8 IQ points by mid-adulthood. The ability to access and utilize memory is one of the factors tested by the IQ test.

Factors that contribute to the development of memory loss include:

  • Early marijuana use
  • Longer length of time using marijuana
  • Higher dose use, especially when combined with frequent and long-term use
  • Underlying mental health disorders, such as depression or anxiety
  • Co-occurring use of other mind-altering substances, such as alcohol or prescription pills


Delta-9-tetrahydrocannabinol, or THC, is the active ingredient in marijuana, and the chemical structure of THC is very similar to the structure of anandamide, a chemical in the brain.

Anandamide is an endogenous cannabinoid, a neurotransmitter that triggers the release of neurons that help the brain communicate with the body. When THC is processed in its place, there is a significant impact on the user’s experience of pain and pleasure as well as their ability to think, concentrate, and remember.

When THC attaches to the cannabinoid receptors, it interferes with the function of the hippocampus and orbitofrontal cortex, the parts of the brain that impact the ability to shift attention, focus, and remember.

“The hippocampus, specifically, processes information and creates memories, so when the use of marijuana interrupts its ability to function normally, both short-term and long-term memory are impaired.”

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Memory loss related to marijuana use indicates a problem with marijuana. Any use of any substance that decreases the ability of the person to function properly requires immediate attention, especially when it negatively impacts relationships, finances, and the ability to take care of oneself proactively.

When a person realizes they are experiencing negative side effects of marijuana use, such as memory loss, and still can’t control their use of the drug — either limiting use or stopping all use of the substance — then it is an indication of a marijuana use disorder and the need for treatment.

It is also true, however, that memory loss may not necessarily be caused by marijuana use if there are other underlying or co-occurring disorders at play. For example, living with depression, certain behavioral disorders, and/or trauma may contribute or cause memory loss, which is worsened by marijuana use.

Very often, marijuana is used as a coping mechanism to manage other disorders. Rather than easing the problem, the side effects of use only exacerbate symptoms or cause new problems of their own.


For those who are living with a marijuana addiction, the risk of memory damage grows the longer addiction continues, and the higher tolerance grows.

According to a study published in the Journal of the American Medical Association (JAMA) Psychiatry, about three of every 10 users of marijuana develop a marijuana use disorder with regular use of the drug.

The rate of developing marijuana addiction increases with earlier age of first use and with more frequent use of the drug.

For many, memory damage is one of the many side effects they will have to combat during active use and well into recovery. It’s no small problem.

Marijuana paraphernalia and products on a black wooden table

According to the World Health Organization, marijuana is the No. 1 drug of abuse around the globe.

The potency of marijuana sold on the street and in dispensaries is increasing every year, making it much more difficult to use the drug recreationally without developing an addiction.


Regular use of marijuana has been associated with adverse side effects. Some are listed below:


Cessation of marijuana use can help many people to begin the process of reversing memory loss. For some users, especially those who used the drug in low doses or for a short period, the reversal process may be easier, quicker, and more complete. That is, they may be able to completely reverse the impact on their memory.

Those who used marijuana for a long time and/or in high doses may have a more difficult time regaining what they lost in terms of memory function and accessibility. They may never completely regain the abilities they had before starting marijuana use.


(Dec 2015) Prevalence of Marijuana Use Disorders in the United States Between 2001-2002 and 2012-2013. JAMA Psychiatry. Retrieved from

(2016) The health and social effects of nonmedical Cannabis use. World Health Organization, Geneva. Retrieved from

(Feb 2016) Association between lifetime marijuana use and cognitive function in middle age: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. JAMA Internal Medicine. Retrieved from

(Jul 2018) Relationship between fMRI response during a nonverbal memory task and marijuana use in college students. Drug and Alcohol Dependence. Retrieved from

(Jan 2012) Adolescent exposure to cannabis as a risk factor for psychiatric disorders. Journal of Psychopharmacology of Oxford England. Retrieved from

(June 2018) How does marijuana produce its effects? National Institute on Drug Abuse (NIDA). Retrieved from

(June 2018) Marijuana, Memory, and the Hippocampus. National Institute on Drug Abuse (NIDA). Retrieved from

(Sep 2015) Recovery from cannabis use disorders: Abstinence versus moderation and treatment-assisted recovery versus natural recovery. Psychology of Addictive Behaviors. Retrieved from

(2014) Is Marijuana an Effective Coping Strategy for Depression or Anxiety? Wentworth Institute of Technology. Retrieved from

(Nov 2011) Intrauterine cannabis exposure leads to more aggressive behavior and attention problems in 18-month-old girls. Drug & Alcohol Dependence. Retrieved from

(Nov 2015). Cannabis exposure and risk of testicular cancer: a systematic review and meta-analysis. BMC Cancer. Retrieved from

(Jul 2016) Marijuana Use and Cardiovascular Disease. Cardiology in Review. Retrieved from[Title+Abbreviation

(Nov 2015). Characteristics and Prognosis of Ischemic Stroke in Young Cannabis Users Compared With Non-Cannabis Users. Journal of American College of Cardiology. Retrieved from

(Jun 2013) Effects of marijuana smoking on the lung. Annals of the American Thoracic Society. Retrieved from

(Feb 2016). Effects of cannabis use on human behavior, including cognition, motivation, and psychosis: a review. JAMA Psychiatry. Retrieved from

(Feb 2013). Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings. PloS One. Retrieved from

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