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Marijuana Legalization Proponents Deny Health Harms Just Like the Tobacco Industry Did

03/18/2013 03:12 pm ET | Updated May 18, 2013

Sooner or later, marijuana legalization proponents will have to take responsibility for grossly misleading the public about the health harms of pot. To persuade people to legalize, they have to perpetuate the myth that marijuana is harmless.

Sound familiar? Denying harm is a tactic used by tobacco companies for 50 years to keep people smoking--and buying--cigarettes. Here's just one of thousands of examples:

"Charges that smoking causes lung cancer and heart disease are outrageous and medically unsubstantiated," Anne Browder, assistant to the president of the Tobacco Institute which represented the tobacco companies, told the Miami Florida News in 1976.

Ethan Nadelmann, executive director of the Drug Policy Alliance, credits his organization as the driving force behind legalizing marijuana, first for medical use and now for recreational use. He says legalization is a policy "grounded in science, compassion, health and human rights." His organization's website presents 10 Facts about Marijuana. Here are just a few, along with summaries of accounts of recent scientific studies reported by Science Daily that show Nadelmann's facts are grounded in neither science or health.

Drug Policy Alliance Fact #3: Claims about increases in marijuana potency are vastly overstated. In addition, potency is not related to risk of dependence or health impacts.

What science says:
High Potency and Synthetic Marijuana Pose Real Dangers in First Weeks of Pregnancy
"Some new, high potency strains, including some medicinal marijuana blends such as 'Connie Chung' and many others, contain up to 20 times more THC, the psychoactive constituent of marijuana, than did 'traditional' marijuana from the 1970's and early 1980's," says study co-author Dr. Delphine Psychoyos, Center for Genetic and Environmental Medicine, Texas A&M University.

High potency THC in today's marijuana, and extremely potent THC analogues found in "synthetic marijuana" brands such as Spice, pose threats to embryonic development as early as two weeks after conception, before a mother even knows she is pregnant, say the authors of this August 2012 study. They point out that research conducted in the past five years has associated marijuana use during pregnancy with anencephaly, attention deficit hyperactivity disorder, learning disabilities and memory impairment in children as well as depression, aggression, and anxiety in teens.

Most pregnant mothers are not aware of the risks marijuana use poses to their unborn children, the authors say. "'This is because many websites on mothering and pregnancy, and those run by pro-marijuana advocacy groups, base their discussions on data collected prior to 1997, when no detrimental effects on pregnancy had been reported.'"

Drug Policy Alliance Fact #4: Marijuana has not been shown to cause mental illness.

What science says:
Cannabis Use Precedes the Onset of Psychotic Symptoms in Young People, Study Finds
This 2011 study involved a random sample of 1,923 young people ages 14 to 24 in Germany. Researchers excluded anyone who had used marijuana or reported psychotic symptoms before the study began and then assessed remaining subjects for marijuana use and psychosis every four years over twelve years.

"Incident [new] cannabis use almost doubled the risk of later incident psychotic symptoms, even after accounting for factors such as age, sex, socioeconomic status, use of other drugs, and other psychiatric diagnoses. Furthermore, in those with cannabis use at the start of the study, continued use of cannabis over the study period increased the risk of persistent psychotic symptoms. There was no evidence for self-medication effects as psychotic symptoms did not predict later cannabis use."

Drug Policy Alliance Fact #5: Marijuana use has not been shown to increase risk of cancer.

What science says:
Marijuana Use May Increase Risk of Testicular Cancer
Testicular cancer is the most common cancer diagnosed in young men ages 15 to 45 and is increasing. Scientists suspect environmental factors are responsible. In 2012, University of Southern California investigators found that men "with a history of using marijuana were twice as likely to have subtypes of testicular cancer called non-seminoma and mixed germ cell tumors. These tumors usually occur in younger men and carry a somewhat worse prognosis than the seminoma subtype. The study's findings confirm those from two previous reports in the journal Cancer on a potential link between marijuana use and testicular cancer."

Drug Policy Alliance Fact #8: Marijuana has not been shown to cause long-term cognitive impairment.

What science says:
Adolescent Pot Use Leaves Lasting Mental Deficits; Developing Brain Susceptible to Lasting Damage from Exposure to Marijuana
A landmark study, published September 2012 in Proceedings of the National Academy of Sciences, found that persistent marijuana use that began before age 18 and continued into adulthood resulted in an average 8-point decline in IQ, enough to drop a person of average intelligence into the bottom third of the IQ scale. The study results were challenged later by another researcher who used simulation models to suggest that other factors such as lower socioeconomic status might have caused the IQ decline. The researchers of the original study reran their data controlling for socioeconomic status and their new results held; the IQ decline occurred in subjects in all socioeconomic levels.

Drug Policy Alliance Fact #9: There is no compelling evidence that marijuana contributes substantially to traffic accidents and fatalities.

What science says:
Cannabis Use Doubles Chances of Vehicle Crash, Review Finds
Researchers conducted a meta-analysis [review] of nine studies that looked at the relationship between marijuana use and driving impairment. The review involved a total of 49,411 people and reveals that driving within three hours after consuming marijuana nearly doubles the risk of having an auto crash that results in serious injury or death. The risk is even higher among drivers age 35 or younger.

New Study Shows Cannabis Effects On Driving Skills

In this 2013 study, researchers confined 30 volunteers who were chronic daily marijuana users to a secure research unit for up to 33 days and tested their blood daily for the presence of marijuana. They found that marijuana can be detected in the blood during a month of abstinence.

"This is consistent with the time course of persisting neurocognitive impairment reported in recent studies and suggests that establishment of 'per se' THC legislation might achieve a reduction in motor vehicle injuries and deaths.

Sue Rusche is president and CEO of National Families in Action, Atlanta, Georgia. The organization is leading the But What about the Children? Campaign that promotes tough regulations to prevent a marijuana industry from marketing to children like the alcohol and tobacco industries do.