US scientists have published research suggesting cannabis smoking does not lead to an increased risk of chronic obstructive pulmonary disease (COPD) even among those clinically more likely to develop it.
COPD is the umbrella term for a group of diseases that cause airflow blockage and breathing problems including emphysema and chronic bronchitis.
Researchers at the University of California Los Angeles (UCLA) examined the relationship between cannabis use and the development of COPD in a group of older subjects who were either current cannabis smokers or regular cigarette smokers in the past.
A cohort of long-term, heavy tobacco smokers who either had established COPD, or were at risk of developing it, were followed over an average of more than four years.
The team divided participants into three groups based on self-reported cannabis use – current, former or never cannabis smokers (CMS, FMS or NMS).
They then compared CMS, FMS and NMS, and those with varying amounts of lifetime cannabis use, and found neither former nor current cannabis smoking was associated with evidence of COPD progression or its development.
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.”
The findings are consistent with a similar University of Queensland longitudinal study of 1,173 young adults aged 21 to 30 who smoked cannabis, tobacco, neither or both over nine years.
While those who smoked cigarettes alone, or cigarettes with cannabis, had reductions in their airflow, cannabis did not add to these reductions.
Meanwhile, smoking cannabis alone did not reduce airflow or seem to impact lung functioning, even after nine years of use.
