A team of US scientists has published findings indicating that smoking cannabis does not raise the risk of chronic obstructive pulmonary disease (COPD), even among individuals who are clinically predisposed to the condition.
COPD is the collective term for a range of diseases that obstruct airflow and cause breathing difficulties, including emphysema and chronic bronchitis.
Researchers from the University of California Los Angeles (UCLA) investigated the connection between cannabis use and COPD development in a group of older participants who were either active cannabis smokers or had a history of regular cigarette use.
The study followed a cohort of long-term, heavy tobacco smokers — all of whom either had a confirmed COPD diagnosis or were considered at risk — over an average period exceeding four years.
Participants were divided into three categories according to self-reported cannabis use: current marijuana smokers (CMS), former marijuana smokers (FMS), and those who had never smoked marijuana (NMS).
Comparing these groups, as well as participants with differing levels of lifetime cannabis consumption, the researchers found that neither current nor former cannabis use was associated with signs of COPD progression or new onset of the disease.
The authors report: "A history of current and/or former smoking of marijuana of any cumulative lifetime amount was not found to be associated with a significantly deleterious impact on progression of COPD.
"Among ever-tobacco smokers in the same cohort without COPD at enrolment, self-reported current and/or former concomitant marijuana smoking, including heavy marijuana smoking, was not found to be associated with an increased risk of subsequently developing COPD."
These results align with a comparable longitudinal study from the University of Queensland that tracked 1,173 young adults between the ages of 21 and 30 across nine years, examining those who smoked cannabis, tobacco, both, or neither.
Participants who smoked cigarettes exclusively, or cigarettes alongside cannabis, experienced measurable reductions in airflow — but cannabis use did not worsen those reductions.
Smoking cannabis on its own, meanwhile, produced no reduction in airflow and appeared to have no adverse effect on lung function, even after nine years of ongoing use.