The long-term study of nearly 1,000 New Zealanders from birth to age 38 found that people who smoked marijuana for up to 20 years have more gum disease, but otherwise do not show worse physical health than non-smokers.
Researchers assessed a dozen measures of physical health, including lung function, systemic inflammation and several measures of metabolic syndrome, including waist circumference, high-density lipoprotein (HDL) cholesterol, triglycerides, blood pressure, glucose control and body mass index.
"Physicians should certainly explain to their patients that long-term marijuana use can put them at risk for losing some teeth," said Terrie Moffitt, Professor at Duke University in the US.
"We can see the physical health effects of tobacco smoking in this study, but we do not see similar effects for cannabis smoking," said Madeline Meier from Arizona State University.
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The study's statistical analysis found that the decline in periodontal health in pot smokers was not explained by tobacco smoking, alcohol abuse or less tooth brushing and flossing, researchers said.
The lack of physical health problems among cannabis users also was not attributable to their having had better health to begin with or to living healthier lifestyles, they said.
Other studies on the same participants have shown that marijuana use is associated with increased risk of psychotic illness, IQ decline and downward socioeconomic mobility, said Meier.
"We need to recognise that heavy recreational cannabis use does have some adverse consequences, but overall damage to physical health is not apparent in this study," said Caspi.
The findings were published in the journal JAMA Psychiatry.