• Cannabis – including marijuana, hashish and hash oil – is the most commonly used illegal drug in Canada.
• In the short-term, cannabis generally makes users feel euphoric and relaxed, although reactions vary for different individuals, depending on expectations, the strength of cannabis and the circumstances of use.
• Cannabis, especially in larger doses, can impair perception, judgment, balance, motor coordination and reaction times.
• Operating a motor vehicle while impaired by cannabis puts people at risk. Some marijuana users drink alcohol at the same time. Driving under the combined influence of these two is particularly risky because both drugs affect motor coordination and their effects can be multiplied.
• Cannabis smoking may affect respiratory health. Heavy use can result in chronic bronchitis, frequent phlegm, shortness of breath, frequent wheezing and chest sounds without a cold or pneumonia.
• Heavy chronic marijuana smokers use health care services more frequently than non-users.
• Using cannabis regularly, and from a young age, increases the risk of harms from cannabis use.
• Health Canada has approved the use of marijuana to alleviate symptoms of certain medical conditions, such as AIDS, multiple sclerosis and chronic pain. There is growing evidence of the therapeutic benefits of cannabis. However, further research is warranted and drug delivery systems other than smoking need to be explored.
  

Canadian Center on Substance Abuse
2004 Canadian Addiction Survey

Canadian Health Network
Marijuana, is it safe?  

Substance Information Link
Cannabis Resource Centre

Canadian Public Health Association
The Pot and Driving Campaign