Marijuana opponents just suffered a major blow in an announcement of study results showing that smoking the evil weed does not harm lungs after all.¹ Au contraire! The study actually found that pot smokers performed slightly better on lung function tests compared to nonsmokers. Lung-function tests measure how much air a person can force out in a second after taking a deep breath. The researchers postulate that marijuana smoking teaches users to inhale deeply and hold their breath, which likely explains their superior performance. Note: I’m not advocating either for or against the legalization of marijuana — just informing you of the facts to help you make your own decision.

The study involved more than 5000 young individuals, aged 18 to 30, who smoked about one joint a day for seven years as well as participants who smoked a joint a week over a 20-year period. UCLA pulmonologist Dr. Daniel Tashkin says, “I think that the bottom line is that there does not appear to be any negative impact on lung function from marijuana smoking and that therefore marijuana is not a risk factor for the development of COPD (Chronic Obstructive Pulmonary Disease). Tobacco smoking is the most important risk factor for COPD.”

In fact, the study also included cigarette smokers, and in contrast to the pot-smoking participants, the tobacco smokers showed a steady decline in lung function over the course of the study. That’s an interesting finding given that marijuana typically contains some of the same toxic ingredients found in tobacco. Also, it is important to note that not all pot-smokers in the study emerged free from lung impairment. Those who smoked more than one daily joint did indeed show a decline in pulmonary function, as did those who had more than 10 years of daily “joint exposure.” As Jon Barron always points out, nature hates excess. It also should be mentioned that in all cases, smoking marijuana did irritate the airways and caused coughing.

Why did cigarettes cause damage, but not the moderate smoking of joints? Some scientists postulate that it’s because THC, the active ingredient in marijuana, has anti-inflammatory properties that counteracts any toxic effects. Incidentally, that’s one of the primary reasons marijuana is useful for medical pain relief. Also, as study researcher Stefan Kertesz says, “A marijuana smoker might have a few joints a month, or a small number of joints or pipe bowls a day. That’s never going to be quite as much smoke as a tobacco smoker with a half-a-pack, pack-a-day, or two packs-a-day habit.”²

For pot smokers, this good news gets added to the arsenal of other study results showing “health” benefits from getting high on marijuana. For instance, a 2007 study found that injecting THC into mice cut lung tumor growth in half and significantly curtailed the growth of new tumors.³ Plus, the mice got a nice high, banging into their cages and each other, but that was the extent of the damage. Sure beats chemotherapy. And speaking of chemotherapy, the protective effects of marijuana are well known for those undergoing chemotherapy treatment. Meanwhile, a 2009 study found that THC kills brain-cancer cells while leaving normal cells intact, and other research has found that THC also fights aggressive breast cancer.  Even more, there’s another substance in marijuana called CBD (cannabidiol) that also appears to arrest tumor growth. CBD apparently works by blocking a gene that causes metastasis.⁴

But before you fly to the nearest street corner to score some of the illegal substance, you might want to pay attention to the other side of the argument. Not all the marijuana news is positive. Jon Barron reported on a study a few years ago that found a link between smoking marijuana and contracting testicular cancer. In fact, that link was significant, showing a 70 percent increased likelihood of contracting an aggressive form of the disease if you smoke marijuana. That same article refered to a host of other studies finding negative respiratory effects from smoking, quite in contrast to the study just released. There’s evidence that marijuana impacts male reproductive function in general and can lower sperm count and quality. And, marijuana affects the cardiovascular system in ways that can pose a threat especially to those with pre-existing heart disease, as it increases blood volume and can cause hypotension, putting more strain on the heart.⁵ A Harvard study found that within an hour of smoking pot, the risk of heart attack goes up five times for the average middle-age person.⁶

Most of all, though, marijuana has psychoactive effects that don’t work for everyone. For those teetering on the edge of psychosis, marijuana smoking can be disastrous, triggering full-blown episodes and worsening symptoms of schizophrenia. Long-term pot smokers have higher rates of depression, anxiety, and other psychiatric disorders than non-smokers.⁷ And Bill Maher aside, they earn less and have lower levels of achievement than nonsmokers. They also tend to have impaired memory, and there’s some evidence that they suffer from cognitive impairment in learning and attention. On the other hand, at least some studies show that the negative cognitive effects wear off within a month of quitting.

The bottom line is that marijuana is still illegal, and so even if it does offer some positive effects, you have to break the law to reap the benefits, unless you have a prescription for medical marijuana, which in some states is remarkably easy to get. In any event, the teen set seems to have decided in favor of the weed. According to a study just released by the National Institute on Drug Abuse, kids are smoking far fewer cigarettes and drinking far less alcohol than in years past, but smoking more pot.⁸

Now, for a bit of anti-marijuna nostalgia, check out some scenes from the classic, “Refer Madness.”

¹ O’Connor, Anahad. “Marijuana Smoking Does Not Harm Lungs, Study Finds.” 11 January 2012. New York Times. 12 January 2012. <http://well.blogs.nytimes.com/2012/01/11/marijuana-smoking-does-not-harm-lungs-study-finds/?ref=health>

² Christopher Wanjek and Stephanie Pappas. “Casual Marijuana Smoking Not Harmful to Lungs.” 10 January 2012. Live Science. 12 January 2012. <http://www.livescience.com/17837-marijuana-lung-health.html>

³ Laino, Charlene. “Marijuana May Fight Lung Tumors.” 17 April 2007. CBS News. 12 January 2012. <http://www.cbsnews.com/stories/2007/04/17/health/webmd/main2696726.shtml>

⁴ “Cannabis compound ‘halts cancer.'” 19 November 2007. BBC. 12 January 2012. <http://news.bbc.co.uk/2/hi/7098340.stm>

⁵ Jones, RT. “Cardiovascular system effects of marijuana.” The Journal of Clinical Pharmacology.” 12 January 2012. <http://jcp.sagepub.com/content/42/11_suppl/58S.short>

⁶ Cromie, William. “Study: Intelligence, cognition unaffected by heavy marijuana use.”

⁷ “Effects of Heavy Marijuana Use on Learning and Social Behavior.” Narcanon. 12 January 2012. < http://www.theroadout.org/drug_information/marijuana/effects_of_heavy_marijuana_use_on_learning_and_social_behavior.html>

⁸ Conley, Mikaela. “Teen Smoking, Drinking Down, Marijuana Use Up.” 14 December 2011. CBS News. < http://abcnews.go.com/Health/teen-smoking-drinking-historical-lows/story?id=15148934#.Tw-hiIG8Gso>