Cigarette smoking is associated with reduced airflow in young adults with or without cannabis use, and cannabis use has no consistent association in young adults related to lung function with or without cigarette smoking, according to study findings published in Respiratory Medicine.

Researchers assessed the association between lung function and cigarette smoking, cannabis use, and co-use of both substances in young adults.

Investigators analyzed data on the children of pregnant women who took part in a longitudinal prospective cohort study, enrolling in the study in the early 1980s. Of the 7223 individuals in this study’s birth cohort, 3805 (52.7%) responded to interview questions at 21 years of age; of these respondents, 2601 also received a spirometry assessment at that time measuring forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and ratio of FEV1 to forced vital capacity (FVC). At age 30, a total of 2900 (40.0%) individuals from the birth cohort responded to interview questions, and 1713 received of these respondents underwent spirometry assessment. Overall, 1173 individuals completed interviews and spirometry at 21 and 30 years of age. Investigators noted some respondents completed the interview but did not participate in the spirometry, and some completed the spirometry but not all of the interview.

Investigators used the cohort with data available at both assessments for comparisons of tobacco and cannabis use. For assessment of combined use of tobacco and cannabis, they used only data from the 30 year-old cohort. The researchers conducted analyses of variance and covariance to assess associations between tobacco and cannabis use and lung function at 30 years, adjusting for physical activity score, education, body mass index, and potential confounders at 30 years. For continuing use of tobacco and cannabis, adjustments were also made for lung function at 21 years, cannabis use (adjusted for cigarette smoking), and tobacco use (adjusted for cannabis use). Sensitivity analyses showed similar results consistent with those of analyses of variance and covariance.

Our findings regarding cannabis use are suggestive of few if any harms associated with relatively low levels of cannabis use evident in a young adult sample.

Data on cigarette smoking and cannabis use was dependent on participants’ responses to the question of how many cigarettes they smoked per day in the last week at ages 21 and 30. At age 21, participants were asked how often they used cannabis in the last month, whether they used cannabis but not within the last month, or whether they had never used cannabis. At age 30, they were asked if they used cannabis within the last 12 months and how much they used on those days.

Using Cannabis With Tobacco May Not Be Worse Than Tobacco Smoking Alone