Marijuana has been used as a scapegoat for many awful events in US history, with the political class blaming the drug for driving Mexican immigrants insane, filling black men with a bloodlust for white women and driving good girls into dens of iniquity.

In the year 2011, such claims ring no more true than any event depicted in the 1936 anti-drug propaganda film "Reefer Madness." Yet still, echoes of that madness remain.

David Frum, a former speechwriter for President George W. Bush who now works as editor of his own conservative political website, suggested in a recent opinion essay that last weekend's tragic events in Tucson, Arizona remind him of why the US must continue prosecuting the war on drugs -- and in particular, the war on America's marijuana users.

"After horrific shootings, we hear calls for stricter regulation of guns," he wrote. "The Tucson shooting should remind us why we regulate marijuana.

"Jared Lee Loughner, the man held as the Tucson shooter, has been described by those who know as a 'pot smoking loner.' He had two encounters with the law, one for possession of drug paraphernalia."

Frum's point, however, seems lost in political posturing.

Marijuana is not regulated in the US, as he claimed: it is instead banned, hence no regulations can be applied to an underground market driven by criminals. Regulation of marijuana would indicate a legal sanctioning of that market with recognition of its possible ill-effects. Under regulation, industry standards -- like limits on THC content, specific packaging rules and prohibitions on growers using certain types of pesticides -- would be applied universally.

While Loughner was alleged to have smoked marijuana, and speculation has swirled over whether he was mentally ill, neither has been confirmed as fact.

There is, however, a small population of schizophrenics who are, as one recent study put it, "powerfully affected" by the drug.

These individuals experience higher highs and lower lows than healthy people who ingest cannabis, researchers in the Netherlands found, and when the effects wear off some experience schizophrenic hallucinations that are even worse than before.

At any given time, around 1% of the world's population has schizophrenia, according to the National Institute of Mental Health (NIMH). It was most likely to emerge in males under the age of 40, but women were found to be more susceptible to the mental disorder as they become older.

Marijuana use has not been shown to cause the disease: only to enhance it.

The greatest concern with schizophrenia in teens is not violence, the NIMH found, but suicide. The psychoactive compounds in marijuana tend to cause feelings of elation and well-being, whereas suicidal thoughts have been cited as a known side-effect of some approved and regulated antidepressant medications.

For contrast, America's most popular legal drug, alcohol, played a role in the deaths of "approximately 79,000" Americans from 2001 and 2005, according to the Centers for Disease Control. Deaths resulting from intoxication on marijuana are virtually unheard of.

"After the Tucson shooting, there may be renewed pressure to control the weapons that committed the crime," Frum wrote. "But what about the drugs that may have aggravated the killer’s mental disease? The trend these days seems toward a more casual attitude and easier access to those drugs. Among the things we should be discussing in the aftermath of this horror is the accumulating evidence of those drugs’ potential contribution to making some dangerous people even more dangerous than they might otherwise have been."

The US war on drugs cost taxpayers over $15 billion in 2010 and the vast majority of those arrested were charged with simple possession of marijuana.

Frum did not suggest how the US might make access to marijuana more difficult, but reform advocates point to research showing that many teens today find it easier to procure illegal drugs than alcohol or tobacco.

The inflated monetary value of marijuana, kept high by US laws that prohibit its availability to adults in retail settings, has also been cited as a driving cause of Mexico's rising tide of violence. Over 31,000 people have died since Mexican President Felipe Calderon initiated a military crackdown against the wealthy gangs, known to most as drug cartels, which have battled over the lucrative profits generated by America's black market.

In studies of Mexico's growing drug war, researchers have cited America's ease of access to firearms as exacerbating the problem. Loughner, who allegedly killed six people in Tucson on Saturday, purchased his firearm and extended magazine legally.

This video is a trailer for the 1936 film "Reefer Madness."

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