Chandni Hindocha is a 2nd year PhD student researching the interaction between cannabis and tobacco on cognition, dependence and psychotic like effects. She is funded by the Medical Research Council under a four-year PhD in Mental Health. Her interests include a) The individual and combined effects of cannabis and nicotine on subjective and physiological responses, reinforcement and cognition in cannabis and tobacco users; b) The acute and chronic effects of cannabinoids on emotional processing; c) The effects of acute THC and CBD on memory, psychotic-like symptoms, reflective impassivity and enjoyment of music and d) Novel treatments for cannabis dependence.
Introduction: Cannabis and tobacco are common drugs of abuse worldwide and are often used in combination through a variety of routes of administration (ROAs). Recent prevalence statistics suggest one billion people worldwide smoke tobacco (22.6% of adults) and 174 million using cannabis (3.5% of adults) with highest rates of use in Oceania (10.3%)  but this data does not account for co-use. Cannabis and tobacco ROAs are important to investigate as they may confer to higher rates of DSM-IV cannabis abuse, produce aero-respiratory changes to favor cannabis inhalation , and alter the subjective experience of the drug. Here we aimed to provide an overview of how cannabis and tobacco ROAs varied across countries and assess the impact of tobacco ROAs on motivation to use less cannabis and tobacco.
Method: A cross-sectional online survey (Global Drugs Survey 2014) was completed by 33687 respondents (mean age = 27.9; %female = 24.8) who smoked cannabis at least once in the last 12 months. Most common ROA, frequency of cannabis/tobacco use, and questions about motivation to use less cannabis/tobacco were recorded. Binary logistic regression was used to assess the effects of cannabis and tobacco, independently and combined on outcome variables associated with quitting behavior which were aligned with the Stages of Change model . Models were adjusted for gender, age, frequency of cannabis, tobacco (and combined). ‘Most common ROA’ was coded as either non-tobacco ROA (e.g. joint without tobacco, vaporizer) or tobacco ROA (e.g. joint with tobacco).
Results: Tobacco-based ROAs were used by 65.6% of respondents. These were most common in Europe (77.2 - 90.9%) and Australasia (20.7 - 51.6%) and uncommon in the Americas (4.4 - 16.0%). Vaporizer use was most common in Canada (13.2%) and the United States (11.2%). Non-tobacco based routes of administration were associated with a 10.7% increase in odds for ‘desire to use less’ tobacco (OR: 1.107, 95% CI: 1.003, 1.221), 80.6% increase in odds for ‘like help to use less tobacco’ (OR: 1.806, 95% CI: 1.556, 2.095) and a 103.9% increase in the odds for ‘planning to seek help to use less tobacco’ (OR: 2.039, 95% CI: 1.638, 2.539) in comparison to tobacco based routes of administration. Associations between ROA and intentions to use less cannabis were inconsistent. More males (63.8%) than females (36.2%) used tobacco ROAs (χ2(1)=48.51, p<0.001). These users were younger (M=26.23, SD=8.48) than those using non-tobacco ROA users (M=30.79, SD=12.76) (F(1,14622)=1058.94, p<0.001).
Conclusions: Results support considerable global variation in cannabis and tobacco ROAs. Tobacco ROAs are common, especially ‘joints with tobacco’, especially in Europe, but not in the Americas. Tobacco routes are associated with lower motivation to change tobacco use. Given the scale of cannabis and tobacco use, interventions addressing the comorbidity need to accommodate this finding and encourage non-tobacco routes. Alternative ROAs such as vaporizers should be investigated for their harm reduction properties.
Funding Sources: This work was supported by the Global Drugs Survey (self-funded) and the Medical Research Council (PhD awarded to CH).
AW is the founder of Global Drug Survey.