The Clinton Herald, Clinton, Iowa

Food & Health

May 1, 2014

How bad is marijuana for your health?

NEW YORK — The Journal of Neuroscience recently published a study linking recreational marijuana use to subtle changes in brain structure. The researchers, led by Jodi Gilman of Massachusetts General Hospital, identified increased gray matter density in the left nucleus accumbens and some bordering areas. The study was fine, but the media coverage was abysmal. Reporters overstated the findings, mischaracterized the study, and failed to mention previous research done on pot smoking and health.

Goldfish may not have a three-second memory, but some journalists seem to. When a new paper comes out, it's often treated as the first ever and final word on the topic. There is a significant body of literature on the neurological and wider health effects of marijuana, and to ignore it when covering new studies seems to me a form of journalistic malpractice.

A press release from the Society for Neuroscience trumpeted the Gilman study's importance because it looked at casual users rather than regular pot smokers, who form the basis of most marijuana studies. That claim is dubious in the extreme. The subjects averaged 3.83 days of smoking and 11.2 total joints per week. Characterizing these people as casual pot smokers was a great media hook, but it defied common sense. Occasional users wondered if they'd done permanent damage, and parents were concerned that their teen-agers might face profound neurological changes from experimenting with pot. Any reporter who read the study, however, should have known not to take that bait.

Even by the standards of past medical studies, it's a stretch to call these subjects casual pot smokers. Just two years ago, for example, Janna Cousijn and colleagues published a study on a group that she called "heavy" marijuana users. In the average week, they smoked 3 grams of cannabis - approximately 2 grams less than Gilman's casual smokers. (A joint has about 0.5 grams of cannabis.) The justification for calling Gilman's subjects casual smokers is that they didn't meet the criteria for dependence, but when you count up the joints, the study doesn't look so revolutionary.

Many stories also claimed that the Gilman study showed direct causation between pot smoking and brain abnormalities. That's wrong. The study looked at differences between pot smokers and abstainers at a single moment. Only a longitudinal study, examining brain changes over time, could have suggested causation. As a letter writer to the Journal of Neuroscience noted, it's possible that pre-existing brain differences cause some people to seek out marijuana. Gilman's pot smokers also drank more and smoked more cigarettes than the control group, which supports this interpretation and also raises the possibility that other factors led to brain structure differences.

The biggest problem with the coverage of the marijuana study was that it failed to put the new research into context. Valentina Lorenzetti of the University of Melbourne recently published a widely cited review paper synthesizing dozens of studies on marijuana and the brain. Taking the literature as a whole, there is evidence suggesting that marijuana use causes structural changes in three parts of the brain: the frontal lobes, temporal lobes and the cerebellum. The data also reinforces the idea that long-term, heavy smokers experience greater changes than casual users. The studies, however, have serious flaws. They are typically small and have been unable to show that the structural changes cause cognitive impairment. Gilman's study of 20 smokers is a good contribution to the literature, but it doesn't resolve those problems.

If you are considering smoking pot - or quitting - here is what you need to know. Smoking marijuana once is very unlikely to harm you. It takes at least 15 grams of cannabis to kill a person, and probably much more than that. A healthy person would have to smoke dozens of joints in a single session to risk death from overdose. People who do die from the acute effects of marijuana die in accidents: A recent study suggested that more than 10 percent of drivers killed in car accidents test positive for cannabis.

The more likely risk from trying marijuana is dependence. There is a debate over whether marijuana is addictive, but you needn't bother with it - it's mainly about semantics. The fact is, approximately 9 percent of people who start smoking pot become dependent by ordinary medical standards. That's low compared with dependence rates for other drugs: More than 15 percent of people who drink become alcoholics, and 32 percent of people who try cigarettes get hooked. Still, you should think seriously about a 1-in-11 chance of addiction, especially if you have a personal or family history of substance abuse.

Studies consistently show that frequent marijuana smoking is associated with some forms of respiratory dysfunction. Smokers report problems with coughing, wheezing and phlegm. Lung cancer is a murkier issue. Cannabis smoke contains higher concentrations of some carcinogens than cigarette smoke does. Some large studies show increased prevalence of respiratory tract cancers in cannabis users, while others find no correlation.

The cognitive effects of chronic marijuana use are uncertain. If you're an adult who smokes occasionally, there appears to be little or no reason to believe your mental performance will suffer. Several studies also show that those who experience impairments may recover if they stop smoking. Heavy, long-term smokers may experience memory and attention loss.

As with alcohol and tobacco, it's fairly clear that minors should not use marijuana. Many studies show that kids who smoke pot do poorly in school, and some studies suggest that they commit suicide at higher rates. Although the causal relationship isn't clear, the risks are too great.

 

1
Text Only
Food & Health
  • Sunburn isn't the only sign of summer that can leave you itchy and blistered

    You've got a rash. You quickly rule out the usual suspects: You haven't been gardening or hiking or even picnicking, so it's probably not a plant irritant such as poison ivy or wild parsnip; likewise, it's probably not chiggers or ticks carrying Lyme disease; and you haven't been swimming in a pond, which can harbor the parasite that causes swimmer's itch.

    July 31, 2014

  • Fist bump photo Study: Fist bumps less germy than handshakes

    When it comes to preventing the spread of germs, maybe the president is on to something with his fondness for fist bumps.

    July 30, 2014 1 Photo

  • Watermelon Think beyond the slice with refreshing watermelon

    Watermelon is one of those foods you really don’t need to overthink.
    Slice it. Eat it. Spit out the occasional seed. Done.

    July 27, 2014 1 Photo

  • Health insurers owe Iowans nearly $1.8M in refunds

    The federal government says insurers owe Iowans nearly $1.8 million in refunds because of a provision in the Affordable Care Act.

    July 24, 2014

  • Agents get subsidized 'Obamacare' using fake IDs WASHINGTON (AP) — Undercover investigators using fake identities were able to secure taxpayer-subsidized health insurance under President Barack Obama’s health care law, congressional investigators said Wednesday.The weak link seemed to be call cente

    July 24, 2014

  • Almost half of America's obese youth don't know they're obese

    The good news is that after decades of furious growth, obesity rates finally seem to be leveling off in the U.S.. The bad news is that America's youth still appear to be dangerously unaware of the problem.

    July 23, 2014

  • Illinois patients to docs: 'What about marijuana?'

    Illinois doctors, nursing homes, hospitals and hospice organizations are ramping up for their role as gatekeepers in the state's new medical marijuana program.

    July 23, 2014

  • Amanda Stecker Herbs make a better way to flavor meals Summer is a season full of fresh herbs. This is the best time of year to take advantage of the fresh herbs in the grocery store. Herbs add a boost of flavor without added sodium and are rich in antioxidants. Herbs are easy to incorporate into everyda

    July 23, 2014 1 Photo

  • Genome Genetic mapping triggers new hope on schizophrenia WASHINGTON, D.C. — Scientists have linked more than 100 spots in our DNA to the risk of developing schizophrenia, casting light on the mystery of what makes the disease tick.Such work could eventually point to new treatments, although they are many y

    July 23, 2014 1 Photo

  • An oncologist uses scorpion venom to locate cancer cells

    Olson, a pediatric oncologist and research scientist in Seattle, has developed a compound he calls Tumor Paint. When injected into a cancer patient, it seems to light up all the malignant cells so surgeons can easily locate and excise them.

    July 22, 2014

Parade
Magazine

Click HERE to read all your Parade favorites including Hollywood Wire, Celebrity interviews and photo galleries, Food recipes and cooking tips, Games and lots more.