According to the CDC, tobacco kills more people worldwide than HIV, tuberculosis and malaria combined (1;2). One in 5 deaths in the U.S. are attributable to cigarette smoking (1) and over 27.4% of the U.S. population aged 12 and older reported past month use of a tobacco product, primarily cigarette smoking, in 2010 (3). Cannabis (marijuana) remains the most commonly used illicit drug in most developed nations (4). Rates in the U.S. have been stable (5) with recent trends indicating a slight increase, especially in youth (6). Compared with 2002, when 6.2% of those aged 12 and older in the U.S. reported past month cannabis use, 6.9% reported past month use in 2010 (3). In Australia, while population trends also indicate a similar increase from 9.1% in 2007 to 10.3% in 2010, recent cannabis use appears to have declined in youth since 1998 (7). Despite cross-national variations in rates of use, cannabis smoking has been and continues to be associated with adverse effects on school, employment, relationships, cognitive processing, mental health, health (primarily respiratory), and health-care utilization (8). Independently, each
