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Cannabis Legalization is Associated With Higher Teen Asthma Rates, Study Finds

By Leo Bear-McGuinness

Published: Jan 13, 2023   
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US states that have adopted legal cannabis policies have seen significant rises in the proportion of young people diagnosed with asthma, according to a new pre-proof study.

Published in Preventive Medicine, the study – which has not yet been peer-reviewed – compared survey data on child asthma rates in certain US states with the cannabis legalization statuses of those states.

The authors found that, among people aged 12-17, asthma rates had increased in recent years in states that had legalized cannabis, particularly recreational cannabis. This rise in asthma cases was significantly higher than the changes seen in states without legalization.

The study was only observational (no biochemical link between cannabis smoke and asthma was investigated or established), but the authors say their evidence still suggests that legal cannabis use may be related to increasing asthma rates.

Breaking down the data

To get their findings, the research team – led by researchers from the City University of New York – trawled through data from National Survey on Children’s Health from 2011 to 2019. A total of 227,451 children aged 0-17 years old were included in the final data set.

The team then compared the proportion of children with asthma in states that had legalized medical and recreational cannabis and the states that hadn’t enacted legalization policies.

Overall, between 2011 and 2019, child asthma rates decreased in all three kinds of states, although reductions were greater in states without cannabis legalization or recent medical cannabis legalization.

By age, asthma rates decreased, from their 2011-2012 figures, for children between the ages of 0 and 11 in all three kinds of states.

Among youths aged 12-17, however, the prevalence of asthma significantly increased in states that had legalized cannabis, particularly recreational cannabis. There was a 1.86% increase in asthma rates among this cohort between 2016-2017 and 2018-2019.

As for ethnicity, the researchers noted that asthma rates slightly increased (from 2011-2012 figures) among Hispanic youth in all three state categories. This trend was not exactly observed among non-Hispanic White and Black children.

Is there a link?

The research didn’t measure or demonstrate any direct link between cannabis use and developing asthma, but they did postulate on an association and called for further research to investigate the possibility.

“It is plausible that increases in use of cannabis among adults living with minor children, which have been documented in states with RCL [recreational legalization] relative to those without RCL, may lead to increased exposure to SCS [second-hand cigarette smoke] which, in turn, will exacerbate asthma,” they write in their paper.

“Given the cross-sectional nature of these data, it is not possible to determine a sequential or cause-and-effect relationship,” they add. “As such, use of longitudinal data toward obtaining new information about the potential impact of cannabis legalization and commercialization on adolescents’ respiratory health is needed.”

Previous research into the relationship between cannabis smoke and asthma is scant. Indeed, according to the City University of New York researchers, their study is the “first to examine the relationship between changes in cannabis policy and children’s asthma.”

Some previous studies, however, have linked second-hand cannabis smoke with poorer child health.

In one study published in Pediatric Research in 2021, researchers found a statistically significant association between a child’s exposure to second-hand cannabis smoke from a parent and an increased likelihood of catching a viral respiratory infection – such as the common cold or bronchiolitis. Like the City University of New York study, this research observed survey data and did not investigate any biochemical association between cannabis smoke and child respiratory health.

Nonetheless, several other studies have linked cannabis smoke with poorer lung health.

In one study published in the American Journal of Respiratory and Critical Care Medicine last year, researchers found that both tobacco and cannabis smokers had higher static lung scores than non-smokers. Static lung scores are indicative of overinflated lungs.

In 2021, research from the Ottawa Hospital, Canada, found that cannabis smokers experience emphysema at higher rates than both non-smokers and tobacco smokers.

Another 2021 study from researchers at the University of Michigan found that teens who vape cannabis are almost twice as likely to report problems with wheezing and coughing than their peers who use tobacco cigarettes or vape nicotine products. 

Lung cancers, on the other hand, appear to have a null association with cannabis use, despite the presence of carcinogens in cannabis smoke. As for the reasons behind this null effect, one scientific review published in 2015 posited that cannabinoids like THC counteract the carcinogens with their known tumor-suppressant effects.


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