“Our hypothesis from this early work is that these changes may be an early sign of what later becomes a motivation…”

(by Alex Dobuzinskis, Reuters) – Young, casual marijuana smokers experience potentially harmful changes to their brains, with the drug altering regions of the mind related to motivation and emotion, researchers have found.

The study, which was published Wednesday in the Journal of Neuroscience, differs from many other pot-related research projects that are focused on chronic, heavy users of cannabis. [Other studies have revealed brain changes among heavy marijuana users, but this research is believed to be the first to demonstrate such abnormalities in young, casual smokers.]

The collaborative effort between Northwestern University’s medical school, Massachusetts General Hospital and Harvard Medical School showed a direct correlation between the number of times users smoked and abnormalities in the brain.

“What we’re seeing is changes in people who are 18 to 25 in core brain regions that you never, ever want to fool around with,” said co-senior study author Dr. Hans Beiter, professor of psychiatry and behavioral sciences at Northwestern University. [CORRECTION: Rueters notes the name of researcher is Breiter, not Beiter]

In particular, the study identified changes to the nucleus accumbens and the nucleus amygdala, regions of the brain that are key to regulating emotion and motivation, in marijuana users who smoke between one and seven joints a week.

The researchers found changes to the volume, shape and density of those brain regions. But more studies are needed to determine how those changes may have long-term consequences and whether they can be fixed with abstinence, Breiter said.

“Our hypothesis from this early work is that these changes may be an early sign of what later becomes amotivation*, where people aren’t focused on their goals,” he said. [Amotivation is a state of lacking any motivation to engage in an activity, characterized by a lack of perceived competence and/or a failure to value the activity or its outcomes.]

The study, which was funded in part by the National Institute on Drug Abuse and the White House Office of National Drug Control Policy, comes as access to pot is expanding following 2012 votes in Washington state and Colorado to legalize its recreational use. The drug remains illegal under federal law.

Medical pot is allowed in 20 U.S. states.

Pot legalization advocates make the argument that marijuana is safer than alcohol a central part of their campaigns.

Other research has found drinking alcohol alters the brain, Breiter said. But while researchers do not know exactly how the mental rewiring seen in pot users affects their lives, the study shows it physically changes the brain in ways that differ from drinking, he said.

This latest study fits with other research showing marijuana use has significant effects on young people because their brains are still developing, and Breiter said he has become convinced that marijuana should only be used by people under 30 if they need it to manage pain from a terminal illness.

Reprinted here for educational purposes only. May not be reproduced on other websites without permission from Thomson Reuters. Visit the website at Reuters .com.


1. What did researchers find after conducting a study of casual pot smokers?

2. How did the study published this week differ from previous studies?

3. a) What two regions of the brain changed with just limited marijuana use?
b) What do these two areas control?

4. Why are the negative effects of pot use more concerning today than at any other time?

5. a) Who is Dr. Beiter?
b) What does Dr. Beiter conclude after conducting this study?
c) How seriously should this study be taken by those pushing to legalize marijuana in their states? Explain your answer.

6. State governments make large sums of money by legalizing and then taxing marijuana sales. The drug is still illegal under federal law. States ban the sale of cigarettes to people under 18 (and in some cities under 21) as well as banning the sale of alcohol to those under 21.
What responsibility do you think state leaders have to address the findings of this study as it relates to those under 21? Explain your answer.


From a report on the study:

“Anything that underscores that there may be structural changes in the brain [from marijuana use] is important,” said Dr. Staci Gruber, an associate psychiatry professor at Harvard Medical School and a director of brain imaging at McLean Hospital.

Gruber’s studies of marijuana smokers have focused on those with longer, more chronic use and have found that those who started smoking at earlier ages, while still in their teens, are less able to perform certain reasoning and decision-making tasks, compared with those who started later in life.

Stuart Gitlow, president of the American Society of Addiction Medicine, said the Mass. General study provides much-needed “hard evidence” of brain changes that appear to match the changes in cognitive skills – thinking and reasoning – that other researchers have demonstrated in marijuana studies.

“We’ve known that people who use marijuana when they’re younger tend to have cognitive abnormalities, but this gives us direct evidence,” he said.

“It’s fairly reasonable to draw the conclusion now that marijuana does alter the structure of the brain, as demonstrated in this study,” Gitlow said, “and that structural alteration is responsible, at least to some degree, for the cognitive changes we have seen in other studies.” 



Wikipedia warns: 

A 2013 literature review said that exposure to marijuana had biologically-based physical, mental, behavioral and social health consequences and was “associated with diseases of the liver (particularly with co-existing hepatitis C), lungs, heart, and vasculature.” There are insufficient data to draw strong conclusions about the safety of medical cannabis, although short-term use is associated with minor adverse effects such as dizziness. Although supporters of medical cannabis say that it is safe, further research is required to assess the long-term safety of its use.

WebMd gives the following information:  Pain is the main reason people ask for a prescription… It could be from headaches, a disease like cancer, or a long-term condition, like glaucoma or nerve pain.  Doctors also may prescribe medical marijuana to treat:

  • Muscle spasms caused by multiple sclerosis
  • Nausea from cancer chemotherapy
  • Poor appetite and weight loss caused by chronic illness, such as HIV, or nerve pain
  • Seizure disorders
  • Crohn’s disease

The FDA has also approved THC, a key ingredient in marijuana, to treat nausea and improve appetite. It’s available by prescription. 

Example of states where medical marijuana is legal:   

MAINE residents with at least one of the following debilitating medical conditions may ask their doctor for a recommendation for medical use of cannabis:

  • Cancer
  • Glaucoma
  • Positive status for human immunodeficiency virus (HIV)
  • Hepatitis C
  • ALS (Amyotrophic Lateral Sclerosis)
  • Crohn’s disease
  • Agitation of Alzheimer’s disease
  • Nail-patella syndrome
  • Intractable pain, or a chronic or debilitating disease or medical condition or its treatment that produces cachexia, severe nausea, seizures (such as those characteristic of epilepsy) or severe and persistent muscle spasms (such as those characteristic of multiple sclerosis)
  • Chronic pain that has not responded to traditional treatments for 6 months or more.
  • PTSD (Post-traumatic stress disorder) 

CALIFORNIA – A serious medical condition, as defined by SB 420, is any of the following:

AIDS; anorexia; arthritis; cachexia (wasting syndrome); cancer; chronic pain; glaucoma; migraine; persistent muscle spasms (i.e., spasms associated with multiple sclerosis); seizures (i.e., epileptic seizures); severe nausea; any other chronic or persistent medical symptom that either substantially limits a person’s ability to conduct one or more of major life activities as defined in the Americans with Disabilities Act of 1990, or if not alleviated, may cause serious harm to the person’s safety, physical, or mental health.

NEW JERSEY: A physician must certify that a patient has an approved debilitating medical condition to participate in the Medicinal Marijuana Program. Approved debilitating medical conditions include:

  • Amyotrophic lateral sclerosis
  • Multiple sclerosis
  • Terminal cancer
  • Muscular dystrophy
  • Inflammatory bowel disease, including Crohn’s disease
  • Terminal illness, if the physician has determined a prognosis of less than 12 months of life.

The following conditions apply, if resistant to, or if the patient is intolerant to, conventional therapy:  Seizure disorder, including epilepsy, Intractable skeletal muscular spasticity, Glaucoma

The following conditions apply, if severe or chronic pain, severe nausea or vomiting, cachexia or wasting syndrome results from the condition or treatment thereof:  Positive status for human immunodeficiency virus, Acquired immune deficiency syndrome, Cancer

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