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Frequent Marijuana Use in Teens and Young Adults Can Affect the Brain: Researchers

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Using marijuana at least once a week can lead to cognitive decline, poor attention and memory and decreased IQ in teens and young adults, according to researchers at the American Psychological Association annual meeting.

Krista Lisdahl, Director of the Brain Imaging and Neuropsychology Lab at the University of Wisconsin-Milwaukee, noted that 6.5 percent of high school seniors reported smoking marijuana daily, up from 2.4 percent in 1993. Among young adults ages 18 to 25, almost one-third said they had used marijuana in the last month, Lisdahl noted in a news release. She said a 2012 study found people who have become addicted to marijuana can lose an average of six IQ points by adulthood.

“It needs to be emphasized that regular cannabis use, defined here as once a week, is not safe and may result in addiction and neurocognitive damage, especially in youth,” Lisdahl wrote in a study she so-authored in the journal Current Addiction Reports.

Lisdahl noted that brain imaging studies of regular marijuana users have shown significant changes in their brain structure, especially among teenagers. USA Today reports Lisdahl said abnormalities in the brain’s gray matter, which is associated with intelligence, have been found in 16- to 19-year-olds who increased their marijuana use in the past year.

A study of more than 17,000 teenagers in Montana, co-authored by Bettina Friese of the Pacific Institute for Research and Evaluation in California, found people’s acceptance of legalized medical marijuana use appears to have an effect on teens’ perception of the drug’s risks. The study found marijuana smoking was more common in counties where larger numbers of people had voted to legalize medical marijuana in 2004. “People don’t perceive it as a very harmful substance, and these community norms translate to teens,” Friese said. “From the teen study, they do reference legalization: ‘If it was that bad a drug, they wouldn’t be trying to legalize it.’ “

3 Responses to this article

  1. Chuck / August 19, 2014 at 1:28 pm

    This has been presented before, at least just a few years back, I saw such information reported in News Week, it has about four reference, but I never looked them up. I should have. I think the pieces of information were from SAMHSA.

    Ken Wolski, the voice of rational and clear thinking, he said a few things I had not considered. That yes NIDA, CSAT and SAMHSA have a tendency to fund some studies and avoid others. Specially in Neuroscience there has been too many research funding a Brain Disease idea
    With all the respect that I have for Nora Volkow, I mean she had said some stuff that is really straight like when clinicians do not understand conditions well, there is a tendency of blaming the patient for the outcome.

    I have not smoked marijuana since around 198late, but if this study was true I should have been scoring genius and belong to MENSA would have completed two PhD.s I know am only one person and am a poor example.

    I like to see what kind of research design did they use, how can they speculate about someones future intelligence? I know Neuropsychology can make inferences if they had (not always available) WAIS score before a brain injury. But how do they do what might have been?

    Something similar happened when the Drug Free Workplace was funded. Do you remember all of the statistics about employee’s work day lost, height in health insurance cost and premium?, and a number of other similar statistics to tell employer that we needed to test all their employee (except congress of course) for drug use. Turned out those horrible statistics that Drug Free Workplace were pushing and publishing were no studies at all. They were pure guessing, not even estimates., which has a little foundation on science. The just outright made those numbers up. They figure if does where bad, the statistics have to be bad too (let’s talk about “correlation illusion”). Talk about bamboozling employers and the tax paying public. When the studies were done, seems like non, I mean NON of their guesses where correct. I let you do the homework and find out.

    One thing I kept looking for and perhaps I missed after two reading is the amount of subjects in the study?

    I happen to trust science when studies are done honestly and integrity, I trust that they data is correct, and I also trust the public to make the right decision. Unfortunately there is too much number playing and claiming that something is scientific when it is not. Specially amongst clinicians. If the data is correct I don’t care if it proves how bad marijuana is. But please give me the truth. I think that is one of the reasons I choose to live in a “democracy” that we will loose fast. If politicians both from the right and left of the spectrum continue to manipulate data in bad faith.

    Am so sorry that the public and clinicians are science illiterate,not many people can have clear thinking.

    Neither Obama or any other president can make wise decisions and statement without good data. No amount of wishful thinking will change facts. And I don’t think people understand how dangerous this conditions can be. We can loose our freedoms real quick (in fact we have lose some already)if we are not provided with clear data.

  2. Ken Wolski / August 15, 2014 at 11:39 pm

    Excuse me if I’m less than impressed with new “Scare Studies” about marijuana. The only studies the government funds are studies designed to find harms associated with marijuana, not studies that explore possible benefits of marijuana. I’ve seen so many of these studies over the preceding decades that warned of dire consequences of marijuana use that proved to be false or misleading or quite the opposite upon further study. Take for example the government warning that marijuana dampened the immune system and thus people with a compromised immune system should not use marijuana. This despite the fact that AIDS victims who were using marijuana at the time were living longer than AIDS victims who were not using marijuana. It turned out that marijuana did, in fact, dampen the immune system response, but only when the immune system was attacking its host in autoimmune diseases like AIDS. The new Scare Studies will prove just as bogus as the old Scare Studies did, because nothing changes the fact that thousands of years of marijuana use have not resulted in dysfunctional or harmful brain changes.

  3. jeff kushner / August 13, 2014 at 9:24 pm

    I wonder what President Obama has to say about this. I guess alcohol is no different than marijuana???

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