The state of California's recent step toward fully decriminalizing the possession of small amounts of marijuana with Prop 19 has reignited one of the more contentious flash points in modern society—where, if anywhere, marijuana has a place.

Few things illustrate the controversy better than a comparison of the web pages that purport to separate myth from fact published by the Drug Enforcement Administration (DEA) and the Drug Policy Alliance (DPA). They are almost mirror images of one another, addressing the very same points, but drawing on different studies to reach their preferred conclusions. It's stunning to see how differently these agencies can interpret the same information.

There is a single salvation from this cherry-picking point-counterpoint: the seminal report "Marijuana and Medicine: Assessing the Science Base." This comprehensive summary of marijuana was written in 1999 by the most highly regarded nongovernmental medical organization in the country, the Institute of Medicine, and it serves as the primary source for the information in this article concerning the risks and benefits of marijuana.

Health Risk Myths & Realities

The essential questions are whether the active ingredient in marijuana, a cannabinoid (chemical compound) known as THC, has any medicinal value; whether the risks associated with its use outweigh the benefits; and whether THC answers a need not currently met by any other medications on the market. In the course of that debate, several health risks are often cited:

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Marijuana overdose

There is no existing evidence of anyone dying of a marijuana overdose, but this doesn't preclude the possibility of experiencing adverse or unpleasant effects when it is consumed in large amounts. For comparison's sake, alcohol overdoses claim approximately 5,000 casualties per year.This is often cited as a reason that marijuana is safer than other drugs, like alcohol.

Memory

Marijuana does impair short-term memory, but only during intoxication. THC has been shown to have a negative effect on memory, and chronic abuse of marijuana will cause permanent impairment.

Addiction

The DEA's general opposition to marijuana is comprised of 1) that whatever medical value it has is already fulfilled by other, equally effective drugs on the market, and 2) that marijuana is highly addictive.

Both points can be turned upside down: There is already an abundance of drugs that do the same job as products already on the market, and they receive approval anyway. This seems to run contrary to the DEA's first argument. And even a cursory look at many of the Schedule II opiates and amphetamines shows that high addiction potential is not a basis for legal classification of drugs. The point is that marijuana is not physically addictive, and even if it was, the DEA would appear to be quite hypocritical arguing this point.

The immune system

If smoked marijuana were to inhibit the activity of T-lymphocytes in the blood, it would compromise the body's ability to fight infection. This would put some people at the mercy of opportunistic infections and diseases, notably those who have immunosuppressive conditions like HIV or lymphoma.

However, the data does not support this. What it does support -- barely -- is the compromised immunity of the lungs due to the smoke from marijuana.

Heart problems

It is accepted in medical circles today that marijuana use causes no evident long-term cardiovascular problems for normal persons. The DEA aggressively goes after this point, claiming that according to Harvard researchers, in the hour after having smoked marijuana, one's heart attack risk goes up five fold. However, this 'fact' is not properly cited and is indicative of the DEA's sloppy attempts to cite its sources. Marijuana's effects on blood pressure are complex and inconsistent as of yet.

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Cancer

Is THC considered a carcinogen (cancer-causing) in humans? Not according to the two most esteemed agencies of relevance, the International Agency for Research on Cancer (IARC) and the U.S. National Toxicology Program (NTP). However, the same cannot be said for smoking marijuana, as the smoke from burning marijuana shares an array of dangerous and potentially carcinogenic chemicals with cigarette smoke. The DPA fumbles here, saying "there have been no reports of lung cancer related solely to marijuana," subtly hinting that it's even possible to determine causation for any cancer in the first place. It should be said that although the DPA's information is generally more reliable than the DEA’s, it does contain its fair share of porous arguments.

The gateway effect

Does marijuana use lead to harder drugs? Most long-term studies show that those people who report having tried disparate drugs like cocaine and heroin often share a history of having smoked marijuana. However, the implication that marijuana causes people to try harder drugs is as yet unproven, and indeed it may act as an alternative to more dangerous drugs.

Potential benefits

No serious proponent of medicinal marijuana would claim it cures anything. Marijuana does, however, treat symptoms -- pain, nausea -- that are caused by a wide range of illnesses.

Pain management

The receptors in the brain that allow uptake of cannabinoids (like THC) are actually part of the most widespread receptor system in the body. Not only is the body naturally attuned to these molecules, it also uses them to great effect -- numerous studies have established that cannabinoids help reduce pain and other distressing symptoms.

Antiemesis

Some chemotherapy regimens are notorious for causing terrible bouts of nausea and vomiting, and both THC and marijuana have been explored as antiemetic (antinausea) medication. Smoking marijuana does give the desired effect in a matter of minutes and could, therefore, relieve the symptom quickly.

The potential drawback

If marijuana becomes fully legalized in plant form and open to commercialization -- a stance largely supported by the National Organization for the Reform of Marijuana Laws (NORML) -- one notoriously vile group of manufacturers is uniquely poised better than any other to take control of the emerging market: Big Tobacco. Having fully established its disinterest in the public health generations ago by the shady promotion of smoking, the idea of Big Tobacco becoming the nation's pot supplier should frighten anyone favoring legalization and regulation.

Still much to learn

The dearth of useful clinical trial data—randomized, controlled, double-blind trials involving large patient populations—is the biggest hurdle facing marijuana's legitimacy. While numerous smaller tests have been performed that support both sides of the health argument, political and economic reasons will form the primary impetus for the legalization of marijuana. For a state like California, whose budget deficit amounts to billions of dollars, the potential tax revenue from legalized marijuana is a lot of money that is currently going up in smoke.