Tobacco, alcohol, and marijuana: One of these things is not like the other

I saw two things last night which I thought were worth noting. The first was a study published in JAMA entitled, Association Between Marijuana Exposure and Pulmonary Function Over 20 Years:

Context Marijuana smoke contains many of the same constituents as tobacco smoke, but whether it has similar adverse effects on pulmonary function is unclear.

Objective To analyze associations between marijuana (both current and lifetime exposure) and pulmonary function.

Design, Setting, and Participants The Coronary Artery Risk Development in Young Adults (CARDIA) study, a longitudinal study collecting repeated measurements of pulmonary function and smoking over 20 years (March 26, 1985-August 19, 2006) in a cohort of 5115 men and women in 4 US cities. Mixed linear modeling was used to account for individual age-based trajectories of pulmonary function and other covariates including tobacco use, which was analyzed in parallel as a positive control. Lifetime exposure to marijuana joints was expressed in joint-years, with 1 joint-year of exposure equivalent to smoking 365 joints or filled pipe bowls.

Main Outcome Measures Forced expiratory volume in the first second of expiration (FEV1) and forced vital capacity (FVC).

Basically, researchers followed more than 5000 men and women over 20 years to see how smoking tobacco and marijuana affected lung health. What did they find? Not surprisingly, tobacco use had significant negative effects on lung function. Marijuana use, though, had none. No lung effects at all. They couldn’t even show that very high use of marijuana was bad for lung function, although the study wasn’t powered for that analysis. Their conclusions:

Marijuana may have beneficial effects on pain control, appetite, mood, and management of other chronic symptoms. Our findings suggest that occasional use of marijuana for these or other purposes may not be associated with adverse consequences on pulmonary function.

Let’s turn to another legal drug – alcohol. Vital Signs: Binge Drinking Prevalence, Frequency, and Intensity Among Adults — United States, 2010:

Methods: CDC analyzed data collected in 2010 on the prevalence of binge drinking (defined as four or more drinks for women and five or more drinks for men on an occasion during the past 30 days) among U.S. adults aged ≥18 years in 48 states and the District of Columbia; and on the frequency (average number of episodes per month) and intensity (average largest number of drinks consumed on occasion) among binge drinkers.

The results are sort of shocking. More than one in six adults in the US is a binge drinker. Those that do binge drink do so on average more than four times a month, and when they do, they have about 8 drinks on average. More than 28% of binge drinkers were young adults (18-24 years), who had more than 9 drinks on average when binging. But elderly binge drinkers (>65 years) drank the most often, about 5.5 times per month. And don’t forget this:

Binge drinking accounts for more than half of the estimated 80,000 average annual deaths and three quarters of $223.5 billion in economic costs resulting from excessive alcohol consumption in the United States.

So let’s review. Tobacco? Adversely impacts lung function, and perfectly legal. Binge drinking of alcohol? Common, dangerous, and costly to society. Also, totally legal. Marijuana? No impact on lung function, and known beneficial effects. Usually illegal.

I’m not advocating for prohibition or for making tobacco illegal. But I would like someone to offer some good evidence as to why one of these things is not like the other.

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