The Surgeon General’s Warning on Marijuana
http://www.cdc.gov/mmwr/preview/mmwrhtml/00001143.htm
Among the known or suspected chronic effects of marijuana are:
1. short-term memory impairment and slowness of learning.
2. impaired lung function similar to that found in cigarette smokers. Indications are that more serious effects, such as cancer and other lung disease, follow extended use.
3. decreased sperm count and sperm motility.
4. interference with ovulation and pre-natal development.
5. impaired immune response.
6. possible adverse effects on heart function.
7. by-products of marijuana remaining in body fat for several weeks, with unknown consequences. The storage of these by-products increases the possiblilties for chronic, as well as residual, effects on performance, even after the acute reaction to the drug has worn off. Of special concern are the long-term developmental effects in children and adolescents, who are particularly vulnerable to the drug’s behavioral and psychological effects. The “amotivational syndrome,” characterized by a pattern of energy loss, diminished school performance, harmed parental relationships, and other behavorial disruptions, has been associated with prolonged marijuana use by young persons. Although more research is required, recent national surveys report that 40% of heavy users experience some or all of those symptoms.
It's safer than booze!