Cannabis joint. Hands making a cannabis or marijuana joint. Tobacco from a cigarette is being mixed with the dried leaves of the hemp plant (Cannabis sativa, not shown) on tobacco paper. This will be rolled up and a roach (blue rolled up paper) placed in one end to act as a filter. Smoking cannabis can cause mental relaxation, accelerated heart rate, perceived slowing of time and heightened senses. Large doses may result in panic attacks, fear of death and hallucinations. Prolonged use can lead to psychological problems and lung damage. Cannabis is an illegal drug in most countries.