Pot Users' 'Slacker' Reputation Backed By Science

Amanda L. Chan
Updated
young cannabis (Photo: )
young cannabis (Photo: )

By Denise Chow, Staff Writer
Published: 07/02/2013 06:47 AM EDT on LiveScience

The stereotype of pot smokers as lackadaisical loafers is supported by new research: People who smoke marijuana regularly over long periods of time tend to produce less of a chemical in the brain that is linked to motivation, a new study finds.

Researchers in the United Kingdom scanned the brains of 19 regular marijuana users, and 19 nonusers of the same sex and age, using positron emission tomography (PET), which helps measure the distribution of chemicals throughout the brain.

They found that the long-term cannabis users tended to produce less dopamine, a "feel good" chemical in the brain that plays an important role in motivation and reward-driven behavior. [Trippy Tales: The History of 8 Hallucinogens]

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Study participants who smoked marijuana regularly, and those who began using the drug at a younger age, had lower levels of dopamine in a part of the brain called the striatum, which could be why cannabis users appear to lack motivation.

However, "whether such a syndrome exists is controversial," said study lead author Michael Bloomfield, a researcher at the Institute of Clinical Sciences at Imperial College London.

The people in the study used cannabis quite heavily, they all began using the drug between ages 12 and 18, and they all had experienced symptoms of psychosis while under the influence, the researchers said. Some of these symptoms include experiencing strange sensations while on the drug, or having bizarre thoughts, such as thinking they were being threatened by an unknown force.

Because increased dopamine production has been linked with psychosis, the researchers expected to find higher levels of dopamine in the cannabis users, but instead, their findings suggested the opposite.

Previous studies looking at marijuana's effects on the brain have shown that chronic marijuana use may trigger inflammation in the brain, which could affect coordination and learning, and that cannabis users have a higher risk of schizophrenia.

But the new results suggest more research is needed to understand the potential links between chronic marijuana use and mental illnesses.

"It has been assumed that cannabis increases the risk of schizophrenia by inducing the same effects on the dopamine system that we see in schizophrenia, but this hasn't been studied in active cannabis users until now," Bloomfield said in a statement. The results tie in with previous addiction research showing that substance abusers have altered dopamine systems.

The findings could explain behaviors commonly seen in marijuana users, not only those who may suffer psychosis symptoms or dependence, although further study is needed to better understand the link, the researchers said.

They also said the brain changes are likely reversible — previous studies did not find differences in dopamine production between former marijuana users and people who were never regular users of marijuana.

The detailed results of the study were published online June 29 in the journal Biological Psychiatry.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.com.

Jennifer Aniston

The <a href="http://www.huffingtonpost.com/2012/08/12/jennifer-aniston-engaged-justin-theroux_n_1771083.html">recently engaged star</a> is <a href="http://www.elle.com/pop-culture/cover-shoots/women-in-hollywood-2011-605864#slide-1">no stranger to pregnancy rumors</a>. <a href="http://www.gq.com/entertainment/movies-and-tv/201203/jennifer-aniston-paul-rudd-gq-march-2012-cover-story">But she told GQ earlier this year</a> that one persistent baby rumor might have come after she kicked the cigarette habit. "Well, I recently quit smoking, and you do put on some extra pounds," she told the magazine. "It makes a difference, especially if you're not 20."

Barack Obama

The POTUS, who started lighting up as a teenager, had a long battle with nicotine addiction. "I constantly struggle with it," he said in a 2009 news conference, <a href="http://www.huffingtonpost.com/2011/02/08/michelle-obama-president-_n_820340.html">HuffPost previously reported</a>. When he was first deciding to run for president, now first lady Michelle Obama said one of her requirements was that he kick the habit once and for all. And while he tried to quit during his 2008 campaign, it wasn't until 2011 that his wife broke the news that he had been smoke-free for a year, <a href="http://www.huffingtonpost.com/2011/02/08/michelle-obama-president-_n_820340.html">according to the HuffPost report</a>. Later that year, President Obama's doctor also confirmed that he successfully quit smoking, <a href="http://blogs.wsj.com/health/2011/11/01/obamas-doctor-says-hes-fit-for-duty-and-tobacco-free/?mod=WSJBlog&mod=WSJ_health">the Wall Street Journal reported</a>.

Gisele Bundchen

The model -- <a href="http://videos.huffingtonpost.com/entertainment/gisele-bundchen-confirms-pregnancy-517452968">who is pregnant with her second child</a> with husband and football star Tom Brady -- broke the habit in 2003. "When I quit smoking I gained 15 pounds," <a href="http://www.people.com/people/archive/article/0,,20059627,00.html">she told People magazine in 2006</a>. "So? I prefer myself this way. Nothing is worth your health."

Ben Affleck

For the actor, playing a chain smoker in Smokin' Aces was actually the impetus to give up the habit in real life. "The whole week that I shot, I smoked, like, five packs a day," <a href="http://www.people.com/people/article/0,,20010769,00.html">he told People magazine in 2007</a>. "By the time the movie was over, I was so sick of smoking, I just didn't want to do it anymore, and I quit. I have this celluloid record of the last time I smoked."

Kelly Ripa

The Co-Host of Live! With Michael and Kelly told Shape magazine that she used to be a "closet smoker," Everyday Health reports. And while she quit after having children, she picked the habit back up again. What helped her finally quit for good? Exercise, <a href="http://www.everydayhealth.com/stop-smoking-pictures/9-celebrities-that-successfully-quit-smoking.aspx#/slide-8">she said in the interview</a>.

Kristen Stewart

In May 2012, the Twilight actress <a href="http://www.mtv.com/news/articles/1686170/kristen-stewart-quits-smoking-learns-french.jhtml">revealed in an MTV interview</a> that she was learning French -- and that she had quit smoking! "You can't acknowledge it or else suddenly ... you can't think about it," she said shyly. And she's not the only Twilight starlet who's stubbed out her cigarettes -- co-stars Ashley Greene and Nikki Reed also reportedly stopped smoking, <a href="http://www.eonline.com/news/127306/which-new-moon-castmembers-are-trying-to-be-better-role-models">according to EOnline.com</a>.

Charlize Theron

"I was highly addicted," <a href="http://www.vogue.com/magazine/article/charlize-theron-breaking-away/#1">the actress told Vogue in 2011</a>. "I thought, I don’t smoke like normal people. I smoke to die." While Theron didn't tell Vogue exactly how she quit to avoid "jinxing" it, she reportedly tried both <a href="http://www.allaboutyou.com/health/health-advice/celebrity-ex-smokers-how-they-kicked-the-habit-46298?page=7">yoga</a> and <a href="http://www.huffingtonpost.com/2012/02/11/hypnosis-quit-smoking_n_1248444.html">hypnosis</a>.

Jon Hamm

The Mad Man star is no stranger to smoking on screen -- but he quit smoking behind the scenes at the age of 24, <a href="http://www.people.com/people/jon_hamm/0,,,00.html">according to People.com.</a> "It's glamorous on film, but it's not glamorous waking up and smelling like an ashtray," he told the publication. So how does he handle playing his chain-smoking character, Don Draper? Herbal cigarettes. "They taste like a mixture between pot and soap," <a href="http://www.vulture.com/2008/09/jon_hamm_on.html">he once complained to New York magazine's Vulture.com</a>. "But we’re being realistic -- people did smoke back then. My father smoked everywhere, even in the car, in the summertime, with the windows up -- it was part of life," <a href="http://blog.chron.com/celebritybuzz/2012/03/jon-hamm-smoking-onscreen-is-debilitating/">he told the Houston Chronicle earlier this year</a>.

Katherine Heigl

The actress <a href="http://www.parade.com/celebrity/celebrity-parade/2010/1004-katherine-heigl-life-as-we-know-it.html">told Parade in 2010</a> that she was quitting with the help of electronic cigarettes, a <a href="http://abcnews.go.com/Technology/safe-cigarettes/story?id=12789204#.UH6c_xYiFsc">controversial smoking cessation tool</a>. "I've been doing it for six months. Smoking sucks! The one thing I would say to my kid is, 'It's not just that it's bad for you,'" <a href="http://www.parade.com/celebrity/celebrity-parade/2010/1004-katherine-heigl-life-as-we-know-it.html">she told Parade</a>. "'Do you want to spend the rest of your life fighting a stupid addiction to a stupid thing that doesn't even really give you a good buzz?'" Heigl told David Letterman that she had previously unsuccessfully tried the gum, the patch and the prescription drug Chantix to quit, <a href="http://www.huffingtonpost.com/2010/10/04/katherine-heigl-the-crazy_n_749616.html">HuffPost reported at the time</a>.

This article originally appeared on HuffPost.