Although several studies have investigated the potential health-compromising effects of smoking cannabis, findings have been mixed. While most research has focused on cancers of the head and respiratory tract, there is also evidence that cannabis use is linked with more common respiratory problems such as chronic cough and emphysema, as well conditions such as cardiovascular disease; dental problems; cancers not on the smoke administration route; disturbed sleep; and impairment of the immune system. The literature, however, is still inconclusive.
Recent reviews have highlighted four factors contributing to the lack of consistency in the literature. First, researched cannabis users have often smoked tobacco too, making it difficult to determine the individual effects of cannabis. While several studies have statistically controlled for tobacco use, statistical control has problemsthat limit its reliability. Second, the mean age of study participants has often been below that at which serious health problems tend to emerge. Thus, outcomes may have differed considerably had the sample been older. Third, studies using a case-control design are highly susceptible to underreporting of cannabis use, particularly in regions where cannabis use has serious legal consequences. Fourth, several studies have had too few participants who used cannabis daily or almost daily. This could mislead with regard to heavier use.
No previous study has addressed all four of the major concerns listed above. Thisis the objective of the proposed research.
To identify health concerns relating to long-term cannabis use.
350 participants aged 40+ were recruited. Advertisements sought four types of volunteers: individuals who (1) smoked cannabis but not tobacco; (2) smoked both cannabis and tobacco; (3) smoked tobacco but not cannabis; and (4) used neither substance.
Participants completed a survey addressing substance use, diagnosed medical conditions, health concerns relating to smoking cannabis/tobacco, and general health (measured using the Physical Health Questionnaire and the Short Form 36).
Several significant differences were found among the four groups. With regard to diagnosed medical conditions, the three smoking groups reported significantly higher rates of emphysema than did the Neither Substance group (ps <.001). However, all members of the Cannabis Only group diagnosed with emphysema were former regular tobacco smokers. General health subscales and items addressing smoking-related health concerns also revealed several significant group differences, and these tended to show worse outcomes for the two tobacco smoking groups, particularly the Cannabis and Tobacco group.
The findings were reported in poster presentations at the 2012 National Drug and Alcohol Research Centre Annual Symposium and the 2012 National Cannabis Conference.
Findings suggest avenues for future exploration, including the potentially harm-reducing effects of not mixing tobacco with cannabis.