Marijuana use and risk of lung cancer: A 40-year cohort study

Northern Medical Program, University of Northern British Columbia (UNBC), 3333 University Way, Prince George, BC, V2N 4Z9, Canada, .
Cancer Causes and Control (Impact Factor: 2.74). 07/2013; 24(10). DOI: 10.1007/s10552-013-0259-0
Source: PubMed


Cannabis (marijuana) smoke and tobacco smoke contain many of the same potent carcinogens, but a critical-yet unresolved-medical and public-health issue is whether cannabis smoking might facilitate the development of lung cancer. The current study aimed to assess the risk of lung cancer among young marijuana users.
A population-based cohort study examined men (n = 49,321) aged 18-20 years old assessed for cannabis use and other relevant variables during military conscription in Sweden in 1969-1970. Participants were tracked until 2009 for incident lung cancer outcomes in nationwide linked medical registries. Cox regression modeling assessed relationships between cannabis smoking, measured at conscription, and the hazard of subsequently receiving a lung cancer diagnosis.
At the baseline conscription assessment, 10.5 % (n = 5,156) reported lifetime use of marijuana and 1.7 % (n = 831) indicated lifetime use of more than 50 times, designated as "heavy" use. Cox regression analyses (n = 44,284) found that such "heavy" cannabis smoking was significantly associated with more than a twofold risk (hazard ratio 2.12, 95 % CI 1.08-4.14) of developing lung cancer over the 40-year follow-up period, even after statistical adjustment for baseline tobacco use, alcohol use, respiratory conditions, and socioeconomic status.
Our primary finding provides initial longitudinal evidence that cannabis use might elevate the risk of lung cancer. In light of the widespread use of marijuana, especially among adolescents and young adults, our study provides important data for informing the risk-benefit calculus of marijuana smoking in medical, public-health, and drug-policy settings.

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    • "Increasing number of studies show that cannabis is associated with a variety of psychiatric and somatic diseases, such as anxiety (Degenhardt et al., 2012), schizophrenia (Andr√©asson et al., 1987; Zammit et al., 2002), depression (Lev-Ran et al., 2013), dependence (Cox et al., 2007), lung cancer (Callaghan et al., 2013), and myocardial infarction (Thomas et al., 2014). Still, much of the relationship between cannabis use and health effects remains unclear. "
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    ABSTRACT: Aims This study aimed at examining a possible association between cannabis use in adolescence and future disability pension (DP). DP can be granted to any person in Sweden aged 16 to 65 years if working capacity is judged to be permanently reduced due to long-standing illness or injury. Methods Data were obtained from a longitudinal cohort study comprising 49.321 Swedish men born in 1949-1951 who were conscripted to compulsory military service aged 18-20 years. Data on DP was collected from national registers. Results Results showed that individuals who used cannabis in adolescence had considerably higher rates of disability pension throughout the follow-up until 59 years of age. In Cox proportional-hazards regression analyses, adjustment for covariates (social background, mental health, physical fitness, risky alcohol use, tobacco smoking and illicit drug use) attenuated the associations. However, when all covariates where entered simultaneously, about a 30% increased hazard ratio of DP from 40 to 59 years of age still remained in the group reporting cannabis use more than 50 times. Conclusions This study shows that heavy cannabis use in late adolescence was associated with an increased relative risk of labor market exclusion through disability pension.
    Drug and Alcohol Dependence 08/2014; 143(1). DOI:10.1016/j.drugalcdep.2014.07.038 · 3.42 Impact Factor
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    ABSTRACT: To investigate the association between cannabis smoking and lung cancer risk, data on 2159 lung cancer cases and 2985 controls were pooled from 6 case-control studies in the US, Canada, UK and New Zealand within the International Lung Cancer Consortium. Study-specific associations between cannabis smoking and lung cancer were estimated using unconditional logistic regression adjusting for sociodemographic factors, tobacco smoking status and pack-years; odds-ratio estimates were pooled using random effects models. Sub-group analyses were done for sex, histology, and tobacco smoking status. The shapes of dose-response associations were examined using restricted cubic spline regression. The overall pooled OR for habitual vs. non-habitual or never users was 0.96 (95% CI: 0.66-1.38). Compared to non-habitual or never users, the summary OR was 0.88 (95%CI: 0.63-1.24) for individuals who smoked 1 or more joint-equivalents of cannabis per day and 0.94 (95%CI: 0.67-1.32) for those consumed at least 10 joint-years. For adenocarcinoma cases the ORs were 1.73 (95%CI: 0.75-4.00) and 1.74 (95%CI: 0.85-3.55), respectively. However, no association was found for the squamous cell carcinoma based on small numbers. Weak associations between cannabis smoking and lung cancer were observed in never tobacco smokers. Spline modeling indicated a weak positive monotonic association between cumulative cannabis use and lung cancer, but precision was low at high exposure levels. Results from our pooled analyses provide little evidence for an increased risk of lung cancer among habitual or long-term cannabis smokers, although the possibility of potential adverse effect for heavy consumption cannot be excluded. © 2014 Wiley Periodicals, Inc.
    International Journal of Cancer 08/2013; 136(4). DOI:10.1002/ijc.29036 · 5.09 Impact Factor
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    ABSTRACT: Cannabis sativa (marijuana) is used throughout the world, and its use is increasing. In much of the world, marijuana is illicit. While inhalation of smoke generated by igniting dried components of the plant is the most common way marijuana is used, there is concern over potential adverse lung effects. The purpose of this review is to highlight recent studies that explore the impact upon the respiratory system of inhaling marijuana smoke. Smoking marijuana is associated with chronic bronchitis symptoms and large airway inflammation. Occasional use of marijuana with low cumulative use is not a risk factor for the development of chronic obstructive pulmonary disease. The heavy use of marijuana alone may lead to airflow obstruction. The immuno-histopathologic and epidemiologic evidence in marijuana users suggests biological plausibility of marijuana smoking as a risk for the development of lung cancer; at present, it has been difficult to conclusively link marijuana smoking and cancer development. There is unequivocal evidence that habitual or regular marijuana smoking is not harmless. A caution against regular heavy marijuana usage is prudent. The medicinal use of marijuana is likely not harmful to lungs in low cumulative doses, but the dose limit needs to be defined. Recreational use is not the same as medicinal use and should be discouraged.
    Current opinion in pulmonary medicine 12/2013; 20(2). DOI:10.1097/MCP.0000000000000026 · 2.76 Impact Factor
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