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Heavy Use of Marijuana May Cause Brain Damage

marijuanaThe heavy, daily use of marijuana for an extended period of time can detrimentally change brain structures and cause memory impairments.[1] In fact, researchers found that teens who were heavy marijuana users—smoking daily for approximately three years—had abnormal changes in their brain structures that were related to working memory.1 They performed poorly on memory tasks, which leads to poor academic performance and everyday functioning.1

The brain abnormalities and memory problems were observed during the individuals’ early 20s, which indicates long-term effects of chronic use.1 The memory-related structures in their brains appeared to shrink and collapse inward, possibly reflecting a decrease in neurons.1 These abnormalities look similar to schizophrenia-related abnormalities.1

Previous studies have evaluated the effects of marijuana on the cortex, and few directly compared chronic marijuana use in healthy individuals and individuals with schizophrenia.1 This is the first study to target key brain regions in the subcortical gray matter of chronic marijuana users with structural MRI and to correlate these abnormalities with an impaired working memory.1 Working memory is needed to remember and process information in the moment and transfer it to long-term memory.1

The younger the individuals were when they began heavy, chronic use, the more abnormal their brain regions were shaped.1 In fact, the regions related to memory may be more susceptible to the effects of the drug if abuse starts at an earlier age.1 With the movement to legalize the drug, more research is needed to understand its detrimental effects on the brain.1 In the United States, marijuana is the most commonly used illicit drug, and young adults have the highest prevalence of use.1 Decriminalization may lead to greater use.1

The participants in the study began heavy, daily marijuana use at ages 16 and 17.1 At the time of the study, they had not smoked marijuana for two years.1 A total of 97 individuals participated, including a matched group of healthy controls with no history of substance use disorder, and a group of schizophrenia subjects with a marijuana use disorder.1 Those who used marijuana did not abuse any other drugs.1

Of the 15 marijuana smokers who had schizophrenia, 90 percent began heavily using the drug before the mental disorder developed.1 This strengthens the research that marijuana may be linked to developing schizophrenia in those who are genetically susceptible.1 Therefore, if someone has a family history of schizophrenia, they are increasing their risk of developing the mental disorder themselves by abusing marijuana.1

While both chronic marijuana users and chronic marijuana users with schizophrenia both had related brain changes, the individuals with schizophrenia had a greater deterioration in the thalamus, the communication hub of the brain that is critical for learning, memory, and communication between brain regions.1

Therefore, heavy marijuana use, especially in those with schizophrenia, increases the person’s risk for poor working memory, which negatively effects everyday functioning.1



[1] Nauert, R. (2013). Heavy Pot Use May Damage Brain. Psych Central. Retrieved on December 19, 2013, from http://psychcentral.com/news/2013/12/17/heavy-pot-use-may-damage-brain/63425.html

One Comment

  • alex

    January 23, 2014, 2:31 pm

    Hi, i have been reading your blog and i will definitely bookmark your site, just wanted to say i liked this article. It was helpful to me.

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