The effects of marijuana can be magnified if mixed with other drugs or alcohol. It can often be laced or contaminated with other drugs. This can also alter the effects on an individual.
Long-term effects of marijuana can be more serious and damaging than the short-term effects. Marijuana may also promote cancer of the upper digestive tract. Some reports note an increase in cancer of the tongue in people who smoke marijuana but who have no other risk factors. Normally, such cancers are rare in people under age 60. It has come into question though whether or not weed or pot can cause cancer but there is more evidence for medical studies supporting this theory. It is known that marijuana