Children whose parents smoke or vape cannabis appear to get slightly more respiratory infections, such as colds and flu, than those whose parents just smoke tobacco or don’t smoke at all.
The effect may come from children breathing in second-hand marijuana smoke, says Adam Johnson at Wake Forest School of Medicine in North Carolina. “It would make any [respiratory] virus more symptomatic because you have a child’s lungs being exposed to irritants.”
Children who breathe in second-hand tobacco smoke are known to have more respiratory illnesses, such as asthma, which has led some countries to ban people from smoking in cars with children present. But the effects of cannabis smoke exposure are less studied, especially as people tend to smoke fewer marijuana cigarettes per day than they do tobacco cigarettes.
The new study was done in Colorado, where cannabis was legalised recreationally in 2014. Johnson’s team surveyed 1500 parents of children attending a hospital’s paediatric emergency department for any reason. About 10 per cent of the caregivers smoked or vaped marijuana, while half of those used only marijuana and not tobacco.
Parents were asked about various illnesses their children had had in the past year. Children whose parents smoked or vaped marijuana had an average of 1.3 viral respiratory infections in that time, while those who never smoked and those who only smoked tobacco had about 1 per year.
There was no significant difference in the number of asthma exacerbations between any of the groups – this may have been because they happened at very low rates, of only about 0.2 such incidents per child on average over the year, says the team.
The study doesn’t prove that cannabis smoke caused the infections, as it wasn’t a randomised trial, although the idea is plausible, says Johnson. Relying on parents’ memory of illnesses rather than medical records could also be a limitation.
Research into whether second-hand tobacco smoke is linked with ill health can be complicated by the fact that poorer people tend to smoke more, so lower income might be the real cause of any illnesses. But in this study, smoking or vaping marijuana and not tobacco was linked with higher income and educational levels than average.
Journal reference: Pediatric Research, DOI: 10.1038/s41390-021-01641-0
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