Associations Between Cannabis Use and Physical Health Problems in Early Midlife A Longitudinal Comparison of Persistent Cannabis vs Tobacco Users

IMPORTANCE After major policy changes in the United States, policymakers, health care professionals, and the general public seek information about whether recreational cannabis use is associated with physical health problems later in life. OBJECTIVE To test associations between cannabis use over 20 years and a variety of physical health indexes at early midlife. DESIGN, SETTING, AND PARTICIPANTS Participants belonged to a representative birth cohort of 1037 individuals born in Dunedin, New Zealand, in 1972 and 1973 and followed to age 38 years, with 95% retention (the Dunedin Multidisciplinary Health and Development Study). We tested whether cannabis use from ages 18 to 38 years was associated with physical health at age 38, even after controlling for tobacco use, childhood health, and childhood socioeconomic status. We also tested whether cannabis use from ages 26 to 38 years was associated with within-individual health decline using the same measures of health at both ages. EXPOSURES We assessed frequency of cannabis use and cannabis dependence at ages 18, 21, 26, 32, and 38 years. MAIN OUTCOMES AND MEASURES We obtained laboratory measures of physical health (periodontal health, lung function, systemic inflammation, and metabolic health), as well as self-reported physical health, at ages 26 and 38 years. RESULTS The 1037 study participants were 51.6% male (n = 535). Of these, 484 had ever used tobacco daily and 675 had ever used cannabis. Cannabis use was associated with poorer periodontal health at age 38 years and within-individual decline in periodontal health from ages 26 to 38 years. For example, cannabis joint-years from ages 18 to 38 years was associated with poorer periodontal health at age 38 years, even after controlling for tobacco pack-years (beta = 0.12; 95% CI, 0.05-0.18; P < .001). Additionally, cannabis joint-years from ages 26 to 38 years was associated with poorer periodontal health at age 38 years, even after accounting for periodontal health at age 26 years and tobacco pack-years (beta = 0.10; 95% CI, 0.05-0.16; P < .001) However, cannabis use was unrelated to other physical health problems. Unlike cannabis use, tobacco use was associated with worse lung function, systemic inflammation, and metabolic health at age 38 years, as well as within-individual decline in health from ages 26 to 38 years. CONCLUSIONS AND RELEVANCE Cannabis use for up to 20 years is associated with periodontal disease but is not associated with other physical health problems in early midlife.