A long-term study of approximately 1,000 New Zealanders from birth to the age of 38 has found that people who have smoked marijuana for up to 20 years have more gum disease but otherwise do not show worse physical health than nonsmokers.
The researchers assessed a dozen measures of physical health, including lung function, systemic inflammation, and several indicators of metabolic syndrome, including waist circumference, HDL cholesterol, triglycerides, blood pressure, glucose control, and body mass index.
Tobacco users were found to have gum disease as well as reduced lung function, systemic inflammation, and indicators of poorer metabolic health.
“We can see the physical health effects of tobacco smoking in this study, but we don’t see similar effects for cannabis smoking,” said Madeline Meier, an assistant professor of psychology at Arizona State University and one of the authors of the study.
While study participants who had used marijuana to some degree during the past 20 years showed an increase in periodontal disease from the ages of 26 to 38 years, they did not differ from nonusers on any of the other physical health measures.
Statistical analysis also revealed that the decline in periodontal health among pot smokers was not explained by tobacco smoking, alcohol abuse, or poor brushing and flossing habits. Their lack of physical health problems also wasn’t attributable to having better health to begin with or living healthier lifestyles.
“We don’t want people to think, ‘Hey, marijuana can’t hurt me,’ because other studies on this same sample of New Zealanders have shown that marijuana use is associated with increased risk of psychotic illness, IQ decline, and downward socioeconomic mobility,” Meier said.
“We need to recognize that heavy recreational cannabis use does have some adverse consequences, but overall damage to physical health is not apparent in this study,” said study coauthor Avshalom Caspi, the Edward M. Arnett professor of psychology and neuroscience at Duke University.
“Physicians should certainly explain to their patients that long-term marijuana use can put them at risk for losing some teeth,” said Terrie Moffitt, the Nannerl O. Keohane University professor of psychology and neuroscience at Duke and co-director of the Dunedin Multidisciplinary Health and Development Study, which collected the data.
The study, “Associations Between Cannabis Use and Physical Health Problems in Early Midlife: A Longitudinal Comparison of Persistent Cannabis Vs. Tobacco Uses,” was published by JAMA Psychiatry.
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