For Michele Leonhart, the administrator of the Drug Enforcement Administration, there is no difference between the health effects of marijuana and those of any other illegal drug. "All illegal drugs are bad for people," she told Congress in 2012, refusing to say whether crack, methamphetamines or prescription painkillers are more addictive or physically harmful than marijuana.
在美国禁毒署署长米歇尔·莱昂哈特(Michele Leonhart)看来，大麻引起的健康问题和其他违禁药品引起的健康问题是没有区别的。“所有违禁药品都对人们有害，”她在2012年的时候对国会做了上述表示，但她不愿意评价精炼可卡因、冰毒或处方止痛药是否比大麻更容易上瘾、对身体的危害更大。
Her testimony neatly illustrates the vast gap between antiquated federal law enforcement policies and the clear consensus of science that marijuana is far less harmful to human health than most other banned drugs and is less dangerous than the highly addictive but perfectly legal substances known as alcohol and tobacco. Marijuana cannot lead to a fatal overdose. There is little evidence that it causes cancer. Its addictive properties, while present, are low, and the myth that it leads users to more powerful drugs has long since been disproved.
关于大麻，科学上已经有清晰的共识，认为它对人体健康的害处远比大多数禁药要小，危险性也比酒精饮料和烟草等合法的高成瘾性物品要低，但莱昂哈特的证词反映出，陈旧的联邦法规强制措施与科学共识之间有着巨大的鸿沟。过量使用大麻不会引起致命后果。几乎没有证据表明它能致癌。它虽然有成瘾性，但极其微小，关于它会导致使用者尝试更强烈的毒品这一神话早就被证明是假的。
That doesn’t mean marijuana is harmless; in fact, the potency of current strains may shock those who haven’t tried it for decades, particularly when ingested as food. It can produce a serious dependency, and constant use would interfere with job and school performance. It needs to be kept out of the hands of minors. But, on balance, its downsides are not reasons to impose criminal penalties on its possession, particularly not in a society that permits nicotine use and celebrates drinking.
这并不意味着大麻完全无害；事实上，当前品种的药效可能会令几十年没有尝试过它的人感到震惊，特别是作为食物口服使用。它可以造成严重的依赖，持续使用会影响工作与学习表现。未成年人必须远离它。但是总体来说，它的副作用并不足以支持对持有者施加刑事惩罚，更何况这个社会允许使用尼古丁，还赞美饮酒。

Marijuana’s negative health effects are arguments for the same strong regulation that has been effective in curbing abuse of legal substances. Science and government have learned a great deal, for example, about how to keep alcohol out of the hands of minors. Mandatory underage drinking laws and effective marketing campaigns have reduced underage alcohol use to 24.8 percent in 2011, compared with 33.4 percent in 1991. Cigarette use among high school students is at its lowest point ever, largely thanks to tobacco taxes and growing municipal smoking limits. There is already some early evidence that regulation would also help combat teen marijuana use, which fell after Colorado began broadly regulating medical marijuana in 2010.
大麻对健康的负面作用成为对其采取强硬措施的理由，在限制滥用合法物品方面，强硬措施作用显著。科学界与政府已经获得不少经验，比如说，该怎样让未成年人远离酒精饮料。通过禁止法定年龄以下的人饮酒的强制性法令，以及切实有效的市场宣传，2011年，未成年人饮酒率降低到24.8%，低于1991年的33.4%。受益于烟草税和日渐增加的市政吸烟限制规定，中学生的烟草使用率也已达到有史以来的最低点。已有若干早期证据表明，制定相关规定有助于减少青少年对大麻的使用——2010年，科罗拉多州开始宏观管理医用大麻，青少年对大麻的使用率也随之下降。
Comparing the Dangers
危险性对比
As with other recreational substances, marijuana’s health effects depend on the frequency of use, the potency and amount of marijuana consumed, and the age of the consumer. Casual use by adults poses little or no risk for healthy people. Its effects are mostly euphoric and mild, whereas alcohol turns some drinkers into barroom brawlers, domestic abusers or maniacs behind the wheel.
与其他消遣物相比，大麻对健康的影响视使用频率、药效、使用量，以及使用者的年龄而定。健康的成年人偶尔少量使用，是几乎乃至完全没有任何危险的。大麻的效果主要是令人精神愉快，变得温和，而酒精则会令有些饮酒者在酒吧里惹是生非，在家里施行暴力，或者危险驾驶。
An independent scientific committee in Britain compared 20 drugs in 2010 for the harms they caused to individual users and to society as a whole through crime, family breakdown, absenteeism, and other social ills. Adding up all the damage, the panel estimated that alcohol was the most harmful drug, followed by heroin and crack cocaine. Marijuana ranked eighth, having slightly more than one-fourth the harm of alcohol.
2010年，一个英国独立科学委员会对比了20种药品对个体使用者的伤害，乃至对社会整体的伤害（包括导致犯罪、家庭破裂、旷工旷课，乃至其他社会问题）。将所有的伤害综合在一起后，该小组认为酒精是最有害的物品，海洛因与精炼可卡因紧随其后。大麻位列第八，伤害性约相当于酒精的1/4多一点。
Federal scientists say that the damage caused by alcohol and tobacco is higher because they are legally available; if marijuana were legally and easily obtainable, they say, the number of people suffering harm would rise. However, a 1995 study for the World Health Organization concluded that even if usage of marijuana increased to the levels of alcohol and tobacco, it would be unlikely to produce public health effects approaching those of alcohol and tobacco in Western societies.
联邦政府的科学家说，酒精与烟草带来的伤害较高，主要是因为它们可以合法获取，因此他们认为，如果大麻也合法化、可以轻松获取的话，那么受到伤害的人数也会增加。然而，1995年，世界卫生组织的一项研究推断，即便大麻的使用率增长到和酒精与烟草同样的水平，它在西方社会所引发的公共健康问题也不太可能达到酒精与烟草的程度。
Most of the risks of marijuana use are "small to moderate in size," the study said. "In aggregate, they are unlikely to produce public health problems comparable in scale to those currently produced by alcohol and tobacco."
这项研究声称，使用大麻所带来的大部分危险在等级上处于“很小或中等程度”。“总体而言，它导致的公共健康问题不太可能达到目前烟草与酒精所导致的这种规模。”
While tobacco causes cancer, and alcohol abuse can lead to cirrhosis, no clear causal connection between marijuana and a deadly disease has been made. Experts at the National Institute on Drug Abuse, the scientific arm of the federal anti-drug campaign, published a review of the adverse health effects of marijuana in June that pointed to a few disease risks but was remarkably frank in acknowledging widespread uncertainties. Though the authors believed that legalization would expose more people to health hazards, they said the link to lung cancer is "unclear," and that it is lower than the risk of smoking tobacco.
吸烟会导致癌症，酗酒则会导致肝硬化，而大麻与任何致死疾病之间都没有清晰的因果联系。国家药物滥用研究所的专家们是联邦反毒品行动中的科学力量，他们于6月发布了一份关于大麻对健康损害的报告，指出大麻有若干致病风险，但它也非常坦白地承认，这些风险存在着不确定性。尽管报告作者们相信，大麻合法化会使得更多人蒙受健康风险，但报告也说大麻与肺癌之间的关系“不明确”，而且吸大麻比吸烟的风险要低。
The very heaviest users can experience symptoms of bronchitis, such as wheezing and coughing, but moderate smoking poses little risk. A 2012 study found that smoking a joint a day for seven years was not associated with adverse effects on pulmonary function. Experts say that marijuana increases the heart rate and the volume of blood pumped by the heart, but that poses a risk mostly to older users who already have cardiac or other health problems.
最为频繁的大麻使用者会有支气管炎的症状，比如气喘和咳嗽，但一般用量的使用者风险很小。一项2012年的研究表明，连续七年每日吸一支大麻卷烟不会引起肺功能损害。专家说大麻会加快心率，以及心脏的供血量，但这主要是对已经患有心脏病和其他健康问题的老年使用者有风险。
How Addictive Is Marijuana?
大麻的成瘾性有多高？
Marijuana isn’t addictive in the same sense as heroin, from which withdrawal is an agonizing, physical ordeal. But it can interact with pleasure centers in the brain and can create a strong sense of psychological dependence that addiction experts say can be very difficult to break. Heavy users may find they need to take larger and larger doses to get the effects they want. When they try to stop, some get withdrawal symptoms such as irritability, sleeping difficulties and anxiety that are usually described as relatively mild.
大麻的成瘾性与海洛因完全不能相提并论。戒除海洛因非常痛苦，是对身体的严峻考验。但是大麻可以与大脑中的快乐神经中枢互动，产生强烈的精神依赖，药物成瘾专家说这种联系很难消除。重度使用者可能会需要更大的剂量，才能达到自己想要的效果。想要停止使用时，会出现易怒、睡眠障碍和焦虑等戒断症状，这些症状通常被描述为相对轻微。
The American Society of Addiction Medicine, the largest association of physicians specializing in addiction, issued a white paper in 2012 opposing legalization because "marijuana is not a safe and harmless substance" and marijuana addiction "is a significant health problem."
美国成瘾药物协会是最大的专攻成瘾药物的医生组织，2012年，它发表了一份白皮书，反对大麻合法化，因为“大麻不是一种安全无害的物品”，而且大麻成瘾“是严重的健康问题”。
Nonetheless, that health problem is far less significant than for other substances, legal and illegal. The Institute of Medicine, the health arm of the National Academy of Sciences, said in a 1999 study that 32 percent of tobacco users become dependent, as do 23 percent of heroin users, 17 percent of cocaine users, and 15 percent of alcohol drinkers. But only 9 percent of marijuana users develop a dependence.
不管怎样，这种健康问题远比其他合法或不合法物品所带来的健康问题要轻微得多。药学研究中心是国家科学院的健康分部，它在1999年的一份研究报告中说，32%的吸烟者会上瘾，23%的海洛因使用者会上瘾，17%的可卡因使用者会上瘾，15%的饮酒者会上瘾，但只有9%的大麻使用者会上瘾。
"Although few marijuana users develop dependence, some do," according to the study. "But they appear to be less likely to do so than users of other drugs (including alcohol and nicotine), and marijuana dependence appears to be less severe than dependence on other drugs."
“大麻上瘾者人数很少，但确实有人会上瘾，”这项研究说，“但是和使用其他药品（包括酒精与尼古丁）相比，大麻的成瘾率很低。”
There’s no need to ban a substance that has less than a third of the addictive potential of cigarettes, but state governments can discourage heavy use through taxes and education campaigns and help provide treatment for those who wish to quit.
完全没有必要禁止一种成瘾率不到香烟1/3的东西，但各州政府可以通过征收重税和教育来防止人们大量使用大麻，并对需要戒断的人提供治疗。
Impact on Young People
对年轻人的影响
One of the favorite arguments of legalization opponents is that marijuana is the pathway to more dangerous drugs. But a wide variety of researchers have found no causal factor pushing users up the ladder of harm. While 111 million Americans have tried marijuana, only a third of that number have tried cocaine, and only 4 percent heroin. People who try marijuana are more likely than the general population to try other drugs, but that doesn’t mean marijuana prompted them to do so.
反对大麻合法化的人最常用的论据之一，就是大麻会导致使用者尝试更危险的毒品。但各种广泛研究证明，大麻与使用者升级使用更危险的物品之间不存在因果关系。1.11亿美国人都曾尝试使用大麻，尝试使用可卡因的人只有该数字的1/3，尝试使用海洛因的人只相当于这个数字的4%。在使用大麻的人群中，尝试其他毒品的人数比例要比普通人群为高，但并不是大麻导致了此行为。
Marijuana “does not appear to be a gateway drug to the extent that it is the cause or even that it is the most significant predictor of serious drug abuse,” the Institute of Medicine study said. The real gateway drugs are tobacco and alcohol, which young people turn to first before trying marijuana.
药学研究中心的报告说，大麻“并不是一种入门药物，并不是药物严重滥用的原因，甚至也不是药物严重滥用的重要预示因素”。真正的入门药物是烟草和酒精，年轻人早在尝试大麻之前就已经接触到它们了。
It’s clear, though, that marijuana is now far too easy for minors to obtain, which remains a significant problem. The brain undergoes active development until about age 21, and there is evidence that young people are more vulnerable to the adverse effects of marijuana.
不过，对于未成年人来说，如今获取大麻显然非常容易，这仍然是个严重的问题。大脑发育活动要持续到21岁，有证据表明年轻人更容易受大麻副作用影响。
A long-term study based in New Zealand, published in 2012, found that people who began smoking heavily in their teens and continued into adulthood lost an average of eight I.Q. points by age 38 that could not be fully restored. A Canadian study published in 2002 also found an I.Q. loss among heavy school-age users who smoked at least five joints a week.
2012年，一项新西兰的长期研究表明，从十几岁开始大量使用大麻，并在成年期持续使用大麻的人到38岁时智商会下降8分，无法完全恢复。另一项加拿大于2002年发布的研究表明，学龄期大量使用大麻（每周至少吸五支大麻烟卷）会导致智商下降。
The case is not completely settled. The New Zealand study was challenged by a Norwegian researcher who said socio-economic factors may have played a role in the I.Q. loss. But the recent review by experts at the National Institute on Drug Abuse concluded that adults who smoked heavily in adolescence had impaired neural connections that interfered with the functioning of their brains. Early and frequent marijuana use has also been associated with poor grades, apathy and dropping out of school, but it is unclear whether consumption triggered the poor grades.
这项结论并未完全定案。新西兰的研究受到挪威一个研究者的质疑，他声称社会经济因素也可能导致智商下降。但国家药物滥用研究所最近的专家报告认为，从青春期就大量使用大麻的人的神经连接会受到损害，从而影响大脑功能。过早经常使用大麻也与成绩不佳、缺乏兴趣和辍学有关，但成绩不佳是否由使用大麻导致，目前尚不明确。
Restricting marijuana to adults is more important now that Colorado merchants are selling THC, the drug’s active ingredient, in candy bars, cookies and other edible forms likely to appeal to minors. Experience in Colorado has shown that people can quickly ingest large amounts of THC that way, which can produce frightening hallucinations.
目前，更重要的是把大麻的使用局限在成年人范围之内，科罗拉多州商人正在贩卖掺入四氢大麻酚（这是大麻的活性成分，简称THC）的糖果、饼干，以及其他可食用物品，这对未成年人来说可能很有吸引力。科罗拉多的经验表明人们可以通过食用途径，迅速吸收大量THC，这有可能导致可怕的幻觉。
Although marijuana use had been declining among high school students for more than a decade, in recent years it has started to climb, in contrast to continuing declines in cigarette smoking and alcohol use. Marijuana was found -- alone or in combination with other drugs -- in more than 455,000 patients visiting emergency rooms in 2011. Nearly 70 percent of the teenagers in residential substance-abuse programs run by Phoenix House, which operates drug and alcohol treatment centers in 10 states, listed marijuana as their primary problem.
尽管十年多以来，大麻在高中生中的使用率已经下降，但近年又开始出现攀升，与此同时，吸烟和喝酒的比例一直在下降。2011年，有45.5万名急诊病人被发现使用大麻（以及其他药品）。“凤凰屋”(Phoenix House)在10个州中经营着毒品与酗酒治疗中心，在它所主办的家庭反滥用毒品计划中，近70%的受助青少年将大麻列为自己最初的问题。
Those are challenges for regulators in any state that chooses to legalize marijuana. But they are familiar challenges, and they will become easier for governments to deal with once more of them bring legal marijuana under tight regulation.
这些都是选择将大麻合法化的各州管理者所面临的挑战。但这都是一些熟悉的挑战，各州政府一旦将合法化的大麻置于严格管理之下，问题就会变得容易应付得多。