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Is Cannabis Really That Bad?

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Sabrina Richards reports in The Scientist:

Marijuana is a tricky drug, alternately demonized as a gateway drug and lionized for its medical promise. And while the juries remain out on both sides of the coin, one thing is clear: its use is on the rise. According to the US Department of Human Health and Services, the number of people in the United States who admit to smoking pot in the last month climbed from 14.4 million in 2007 to over 18 million in 2011.

This increase may in part be due to the lack of strong evidence supporting the suspected risks of cannabis use. Indeed, though marijuana smoke carries carcinogens and tar just as tobacco smoke does, definitive data linking marijuana to lung damage is lacking. And a recent long-term study that seemed to conclusively link chronic marijuana initiated in adolescence to a lowered IQ in New Zealanders was quickly challenged by a counter-analysis that pointed to socioeconomic status as a confounding factor. According to survey data from the Centers for Disease Control and Prevention, cannabis use increases in teenagers as marijuana’s perceived risks decline, and researchers—and undoubtedly some parents—are anxious to get to the bottom of the matter.

Take a deep breath

In 2012, a study at the University of California, San Francisco (UCSF) calculated that even smoking a single joint every day for 20 years might be benign, though most participants only smoked two or three joints each month. “I was surprised we didn’t see effects [of marijuana use],” said UCSF epidemiologistMark Pletcher, who led the study.

One assessment of various epidemiological studies points to small sample size and poor study design as reasons for scientists’ inability to nail down a link between cannabis and cancer risk. But some suspect that such a link doesn’t exist, and that marijuana may even have cancer-preventive effects. A 2008 study, for example, suggested that smoking marijuana may reduce the risk of tobacco-associated lung cancer, calculating that people who smoke both marijuana and tobacco have a lower risk of cancer than those who smoke only tobacco (though still a higher risk than non-smokers).

But even Pletcher isn’t sanguine about marijuana’s effects on the lungs, and suspects that there may still be long-term lung damage that can be hard to detect. “We really can’t reassure ourselves about heavy use,” he explained.

Your brain on drugs

There is some evidence to suggest that stoned subjects exhibit increased risk-taking and impaired decision-making, and score worse on memory tasks—and residual impairments have been detected days or even weeks after use. Some studies also link years of regular marijuana use to deficits in memory, learning, and concentration. A recent and widely discussed report on the IQs of New Zealanders followed since birth found that cannabis users who’d started their habit in adolescence had lower IQs than non-users.

In this study, led by researchers at Duke University, “you could clearly see as a consequence of cannabis use, IQ goes down,” said Derik Hermann, a clinical neuroscientist at the Central Institute of Mental Health in Germany who was not involved in the research.

But not 4 months later, a re-analysis and computer simulation at the Ragnar Frisch Center for Economic Research in Oslo countered the Duke findings. Ole Rogeberg contended that socioeconomic factors, not marijuana use, contributed to the lower IQs seen in cannabis users.

Rogeberg’s conclusion counters a sizeable literature, however, which supports a link between pot use and neurophysiological decline. Studies in both humans and animals suggest that people who acquiring a marijuana habit in adolescence face long-term negative impacts on brain function, with some users finding it difficult to concentrate and learn new tasks.

Notably, most studies on the subject suggest that while there may be negative consequences of smoking as a teen, users who begin in adulthood are generally unaffected. This may be due to endocannabinoid-directed reorganization of the brain during puberty, Hermann explained. The intake of cannabinoids that comes with pot use may cause irreversible “misleading of the neural growth,” he said. . .

Continue reading.

Written by LeisureGuy

24 January 2013 at 3:54 pm

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