Frequent inhalation of cannabis smoke over a period of years can lead to bronchitis and other respiratory disorders, cancer of the lung and other parts of the digestive tract. Very high doses can also cause coma in young people, not to mention it may also exacerbate existing mental health problems.

I pity those of you who say that it's a harmless drug.

Alcohol can be addictive unlike the mentioned drug, and yes, it usually has more harmful effects if you consume it a lot, but on the other hand, small controlled consumptions of alcohol are safer than small consumptions of "weed".

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram