Tobacco and alcohol may increase likelihood of using illegal drugs, new study shows

Press release issued: 30 September 2021

The use of legal drugs (tobacco and alcohol) may lead to the use of cannabis, a new study led by the University of Bristol and published in the journal Addiction has found. The study also found evidence that cannabis use may lead to smoking initiation, and opioid dependence could lead to increased alcohol consumption. Additionally, there might be shared risk factors that influence the use of multiple substances.

Dr Zoe Reed, Senior Research Associate in the Tobacco and Alcohol Research Group (TARG) in Bristol's School of Psychological Science and co-author of the paper, said: “Legal consumption of alcohol and tobacco may directly increase the level of illicit drug use. However, the relationships are complex. Consuming one drug does appear to increase the consumption of another, but it may also be the case that people have underlying risk factors which increase their chances of consuming both alcohol and tobacco and illicit drugs.”

The study found evidence for a possible gateway effect between:

Tobacco use and subsequent alcohol and cannabis use
Cannabis use and subsequent tobacco use
Opioid dependence and subsequent alcohol consumption.

Read the full University of Bristol press release

Further information

‘Using Mendelian randomisation to explore the gateway hypothesis: Possible causal effects of smoking initiation and alcohol consumption on substance use outcomes’ by Reed ZE, Wootton RE, and Munafò MR in Addiction