Pubdate: Fri, 03 Jun 2016
Source: Boston Globe (MA)
Copyright: 2016 Globe Newspaper Company
Author: Christopher Ingraham, Washington Post


Long-term marijuana use is not associated with a raft of physical 
health problems, according to a new study, with one surprising 
exception: gum disease.

Researchers led by Madeline Meier of Arizona State University tracked 
the marijuana habits of 1,037 New Zealanders from birth to middle age 
to see what effect those habits have on some common measures of 
physical health, including lung function, systemic inflammation, 
cholesterol levels, blood pressure, body weight, blood sugar, and 
dental health.

What they found was surprising: After controlling for other factors 
known to affect health, especially tobacco use and socioeconomic 
status, marijuana use had no negative effect on any measure of 
health, except for dental health. People who smoked more marijuana 
had a higher incidence of gum disease.

The cause is something of a mystery. Meier and her colleagues did 
find that heavy marijuana users were less likely to brush and floss 
than their not-marijuana-using peers. But even after controlling for 
dental hygiene, the relationship between marijuana use and poor 
dental health persisted.

"In general, our findings showed that cannabis use over 20 years was 
unrelated to health problems in early midlife," the study, published 
in the journal JAMA Psychiatry, found. "Across several domains of 
health (periodontal health, lung function, systemic inflammation, and 
metabolic health), clear evidence of an adverse association with 
cannabis use was apparent for only one domain, namely, periodontal health."

In some domains, marijuana use was associated with better health 
outcomes: "Findings showed that cannabis use was associated with 
slightly better metabolic health (smaller waist circumference, lower 
body mass index, better lipid profiles, and improved glucose 
control)," the study determined. However, these associations were 
fairly small and by no means strong enough to recommend regular 
cannabis use as a weight management strategy.

The findings were more striking when measured against the effects of 
tobacco use over a similar period.

"By comparison, tobacco use was associated with worse periodontal 
health, lung function, systemic inflammation, high-density 
lipoprotein cholesterol levels, triglyceride levels, and glucose 
levels in early midlife, as well as health decline from ages 26 to 38 
years," the study found. Despite some public health concerns about 
legal marijuana being "the next Big Tobacco," marijuana's toll on 
physical health appears to be far smaller.

This, too, is something of a mystery, but it might be at least partly 
a question of volume: A heavy marijuana user might light up several 
joints over the course of a day, but a heavy tobacco user might go 
through several packs of cigarettes in a day. In other words, a heavy 
cigarette smoker is inhaling a lot more smoke than a heavy marijuana 
user. And all that smoke might take a steeper toll on health.

"The general lack of association between persistent cannabis use and 
poor physical health may be surprising," Meier and her colleagues 
write. In part, this is because other studies have shown a link 
between marijuana use and poor health in middle age, especially 
cardiovascular health.

But Meier's research is unique in that it uses longitudinal data, 
tracing the health of the same individuals from birth in the early 
1970s to age 38. Many other studies on the physical health effects of 
marijuana use rely on observations at a single point in time, which 
is useful but less reliable for tracking effects over a lifetime.
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MAP posted-by: Jay Bergstrom