Prohibitionist groups like Smart Approaches to Marijuana make lots of stupid claims about cannabis risk, but just how pernicious is the popular plant? Per an exhaustive study published this month in the Journal of the American Medical Association (JAMA) Psychiatry, long-term cannabis consumption is about as perilous as failing to floss. Sure, that might sound a red alert among overzealous dentists, but it should comfort the dozens of people who still believe cannabis sextuples your risk of becoming a schizo.
The study went something like this. Arizona State University professor Madeline H. Meier, formerly of Duke University (which collected the data), led an international group of researchers in tracking the cannabis habits and outcomes of more than 1,000 New Zealanders from birth to age 38. The participants, all born in Dunedin between 1972 and 1973, were professionally checked at different ages for a wide variety of characteristics, including socioeconomics, childhood health and cigarette smoking. After controlling for factors like tobacco, the researchers found that most cannabis consumers had slightly better physical health, save for their gums.
"Our findings showed that cannabis use over 20 years was unrelated to health problems in early midlife,” the study concluded. “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.... Findings [also] 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).”
Per the study, heavy cannabis users brushed and flossed less frequently, but even when controlling for this factor, the smokers still had higher rates of dental health problems. Still, tobacco users had significantly worse dental health, in addition to other issues.
“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," said the study.
The JAMA-published study benefited from longitudinal data provided by health professionals who checked the participants every few years over the course of decades. By comparison, many studies—particularly those of the prohibitionist ilk—base their findings on less reliable self-assessment surveys and observational data collected at a single point in time. The new study certainly counters many long-time health claims made about the dangers of cannabis, but if smoking does negatively affect dental health, cannabis consumers should prioritize dental health routines in their daily lives.
Interestingly, a Maier-led group published findings in Proceedings of the National Academy of Sciences in 2012 that associated long-term cannabis use with declining IQs. A follow-up study published six months later in the same journal seriously questioned the findings, and additional studies—including a large-scale University College of London study published in 2014—outright refuted them. Critics of the IQ study point to the sample size, 38 people, as contributing to the flawed findings. By comparison, the current study involved data from 1,037 participants. Moreover, many would argue that her previous study suggests Maier is not biased toward cannabis in either direction.
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