<qa>  What is the most used psychoactive drug in Canada?1.1 Background. Caffeine is the most used psychoactive drug in Canada, with regular consumption by 88 of the adult population and is unique because it is a cradle-to-grave drug. In Canada, coffee is the most commonly consumed source of caffeine, while tea, chocolate and energy drinks are also significantly used. This significant rate of consumption is likely due in part to caffeines actions on the human brain, resulting in increased arousal, elevated mood and cognitive enhancements. The effects of caffeine, at least at levels typically seen in human consumption, are primarily related to its actions at adenosine receptors. Caffeines antagonistic effects on adenosine can be seen after even a single cup of coffee, with increased consumption resulting in increased blockade. Adenosine receptors are distributed in all brain cells, contributing to the caffeines ability to affect a wide range of brain regions. 