The main objective of the study is to explore associations between alcohol consumption and marijuana use in young adults and to discuss the opportunities for brief intervention.

Face to face structured interviews were carried out with 2,221 young adult Czechs (mean age 29.9, sd. 5.8 years). 51.4% were males. Alcohol consumption was calculated using beverage specific quantity frequency method. Alcohol-related problems were assessed using the Czech version of the AUDIT. Frequency of marijuana use in the last twelve months was asked as well.

The overall alcohol consumption was 9.2 litres of pure alcohol per person and year. The last year prevalence of marijuana use was 21.8%. Marijuana use positively correlated with the frequency of beer drinking (r=.27), frequency of heavy episodic drinking [HED] (r = .32) and with the summary score in AUDIT (r = .39). Harmful or problem drinkers (AUDIT score >16) reported marijuana use more frequently than moderate drinkers (60% compared to 18.8%; OR = 6.54; 95% CI = 4.7; 9.1). OR for marihuana use in heavy episodic drinkers was 4.3 (95% CI = 3.3; 5.6).

The results suggest that frequent HED and harmful drinking are closely associated with marijuana use in younger adults. Since marijuana use (including heavy use) is rather common in the Czech Republic, it would be recommendable to also extend screening and brief intervention to reduce the use of cannabis. The existing guidelines for brief intervention should be modified in order to cover marijuana consumption as well.