[ilovetv]

Originally Posted by JP

I am in favor of out and out legalization. I think marijuana is a lot less harmful than alcohol and it can be medically beneficial.

No way!!

NIH - National Institute on Drug Abuse

Marijuana's Lasting Effects on the Brain

"...They [research studies] have shown that exposure to cannabinoids during adolescent development can cause long-lasting changes in the brain’s reward system as well as the hippocampus, a brain area critical for learning and memory.

The message inherent in these and in multiple supporting studies is clear. Regular marijuana use in adolescence is part of a cluster of behaviors that can produce enduring detrimental effects and alter the trajectory of a young person’s life—thwarting his or her potential.

Beyond potentially lowering IQ, teen marijuana use is linked to school dropout, other drug use, mental health problems, etc. Given the current number of regular marijuana users (about 1 in 15 high school seniors) and the possibility of this number increasing with marijuana legalization, we cannot afford to divert our focus from the central point: Regular marijuana use stands to jeopardize a young person’s chances of success—in school and in life.

September 10, 2012 - We repeatedly hear the myth that marijuana is a benign drug—that it is not addictive (which it is) or that it does not pose a threat to the user’s health or brain (which it does). A major new study published last week in Proceedings of the National Academy of Sciences (and funded partly by NIDA and other NIH institutes) provides objective evidence that, at least for adolescents, marijuana is harmful to the brain.

The new research is part of a large-scale study of health and development conducted in New Zealand. Researchers administered IQ tests to over 1,000 individuals at age 13 (born in 1972 and 1973) and assessed their patterns of cannabis use at several points as they aged. Participants were again tested for IQ at age 38, and their two scores were compared as a function of their marijuana use. The results were striking: Participants who used cannabis heavily in their teens and continued through adulthood showed a significant drop in IQ between the ages of 13 and 38—an average of 8 points for those who met criteria for cannabis dependence. (For context, a loss of 8 IQ points could drop a person of average intelligence into the lowest third of the intelligence range.) Those who started using marijuana regularly or heavily after age 18 showed minor declines. By comparison, those who never used marijuana showed no declines in IQ.

Other studies have shown a link between prolonged marijuana use and cognitive or neural impairment. A recent report in Brain, for example, reveals neural-connectivity impairment in some brain regions following prolonged cannabis use initiated in adolescence or young adulthood. But the New Zealand study is the first prospective study to test young people before their first use of marijuana and again after long-term use (as much as 20+ years later). Indeed, the ruling out of a pre-existing difference in IQ makes the study particularly valuable. Also, and strikingly, those who used marijuana heavily before age 18 showed mental decline even after they quit taking the drug. This finding is consistent with the notion that drug use during adolescence—when the brain is still rewiring, pruning, and organizing itself—can have negative and long-lasting effects on the brain....."

Marijuana's Lasting Effects on the Brain | National Institute on Drug Abuse