Cannabis smoke, for example, contains cancer-causing toxins. However, the risk of developing some cancers (e.g., mouth, tongue and lung) is less for cannabis smokers than tobacco smokers, partly because they tend to smoke less than tobacco users. And, while all drugs have an effect on the brain, the particular properties of the drug influence the level of risk of harmful consequences. The negative effects of cannabis on the brain, for example, seem to be less than the effects of some substances such as alcohol. The psychoactive substance that produces the “high” associated with marijuana is known as tetrahydrocannabinol (THC). THC is one of many chemical compounds present in marijuana known as cannabinoids and is the only cannabinoid proven to produce intoxicating effects. canada marijuana buy online of cannabis use can differ, depending on factors such as the strain of marijuana consumed by the user, the level of THC content, and the consumption method.