Cannabis use among U.S. adults with children in the home is on the rise as states continue to legalize the substance for medicinal and recreational use, raising concerns about how secondhand cannabis smoke may be impacting children's health.

In a study published March 17 in Addiction, researchers used the National Survey on Drug Use and Health — an annual cross-sectional survey of the U.S. — to examine the prevalence of cannabis use among adults with children in the home over a 13-year period, from 2004 to 2017.

"I have been doing research on childhood asthma for nearly 20 years and secondhand tobacco smoke is a well-documented risk factor for onset and exacerbation of childhood asthma," Renee Goodwin, lead author of the paper and professor at The City University of New York and Columbia University, told The Academic Times.

"A lot of progress has been made in reducing children's exposure to secondhand smoke over the years," Goodwin said, adding, "But I wondered about how secondhand cannabis smoke might be affecting children's health, especially those with asthma or at risk for asthma."

Indeed, U.S. states continue to legalize cannabis either recreationally or medically, but scientific research has not been able to properly study the effects of secondhand cannabis smoke, according to Goodwin and her colleagues. 

This research — like others showing that frequent youth cannabis use can lead to a drop in IQ — adds to a growing library of studies examining the multifaceted impact of cannabis as restrictions continue to be lowered by states.

"Legalization is moving very quickly, and it seems as though there are potential issues that could use more attention in the formulation of optimal cannabis policy," Goodwin said. 

Using the National Survey on Drug Use and Health, the researchers produced a sample size of 287,624 respondents who were 18 years or older with children in the home. The survey is administered to noninstitutionalized civilians in all 50 states and the District of Columbia, and includes sociodemographic variables such as age, gender, marital status, annual family income, race and ethnicity, educational attainment and strength of state-level tobacco control.

As may be expected, the researchers found that in 2017, past-month and daily cannabis use were more common in states with recreational marijuana laws, followed by states with medical marijuana laws. States where cannabis use is illegal had the lowest rates of use, based on an examination of the survey.

Past-month and daily cannabis use for states with recreational marijuana laws were 11.9% and 4.2%, respectively, compared to 9.3% and 3.2%, respectively, for states with medical marijuana laws. The researchers found that states without legal cannabis reported past-month and daily cannabis use as 6.1% and 2.3%, respectively.

Comparing the sociodemographics of those who reported past-month and daily cannabis use, the study found that recreational legalization appears to increase use among adults with children in the home broadly across nearly all sociodemographic groups. In contrast, the effect of legalization for medical use is concentrated across certain groups including age, income and education, with increased use particularly salient among adults over the age of 50 and among those with higher income and educational attainment.

Goodwin said it seems logical that individuals who reported using medical marijuana were older, "given that with age, the likelihood of diagnosis of conditions for which medical marijuana could be medically prescribed increases."

The researchers also found that, in 2017, the prevalence of cannabis use among adults living with children in states with recreational marijuana laws was actually higher than the prevalence among the general adult population — 11.9% compared to 9.76%, respectively.

"We know from other work that a majority of children's exposure to secondhand tobacco smoke occurs in the home, and that cannabis use is not legal in public and in very few public/commercial outlets, suggesting that it may be more likely to occur inside a residence," Goodwin said.

Although this study does not examine how much exposure is actually occurring, what the impacts of secondhand cannabis smoke are or how adults are consuming cannabis — either inhaling smoke, eating edibles or applying topicals — it does take an important first step by examining the prevalence of cannabis use by adults with children in the home.

"In this paper, we looked at the prevalence of cannabis use reported by adults with children living in the home and the impact of legalization of cannabis on use," Goodwin said. "There was no measure of where the cannabis was used — we don't know whether it was in the home — or whether children were home at the time it was used. So, indeed, this study does not capture any information on children's exposure."

She added that researchers "need to learn a lot more about the impact of secondhand smoke of all types on children and adults. We still need a lot more data on how much exposure is actually occurring."

Goodwin said, though, that this study should show that, "Policymakers and health care providers need to take action to educate and inform caregivers of the potential risks associated with using cannabis with children in the home."

"It took decades for bans to emerge on exposure to secondhand tobacco smoke," she said. "I don't think we need to wait that long to protect children from cannabis smoke."

The study, "Trends in cannabis use among adults with children in the home in the United States, 2004-2017: Impact of state-level legalization for recreational and medical use," published March 17 in Addiction, was co-authored by Renee Goodwin and Melody Wu, The City University of New York and Columbia University; June Kim and Katarzyna Wyka, The City University of New York; Keely Cheslack-Postava, Columbia University; Andrea H. Weinberger, Yeshiva University and Albert Einstein College of Medicine; and Meyer Kattan, New York-Presbyterian/Columbia University Medical Center and New York-Presbyterian/Morgan Stanley Children's Hospital.