Epidemiological evidence for an association between cannabis and lung cancer is limited
and conflicting. Case series have suggested a causative role for cannabis in lung cancer in young adults [14, 15]. The case–control studies published to date have shown both the presence
[16–18] and absence [19] of an association, but have been limited by the inability to quantify use
[16–18], confounding with combined cannabis and tobacco use [16–18], and studies being
undertaken in populations in which use may have serious legal consequences resulting in
potential information bias [16–19] and poor response rates [19].