经济学人下载:大麻和精神疾病

Royal gorilla, Girl Scout Cookies and Fat Banana are just a few of the improbably named strains of high-potency cannabis out there.
Royal gorilla, Girl Scout Cookies和Fat Banana只是名不符实的高效力大麻品种中的几种。

In the former, levels of tetrahydrocannabinol (THC), the chemical behind the psychological effects of cannabis, are above 25%.
前者的四氢大麻醇（THC）含量在25%以上，这种化学成分赋予了大麻心理效应。

Reviewers describe it as "overwhelming" for novices and a "beautiful euphoric couch-locking experience" for others.
评论者称这一含量之强悍是新手难以应付的，对其他人则是一种“美妙的、愉悦的、身体舒畅的体验”。

However enticing that may sound, regular use of cannabis with a potency greater than 10% increases the risk of developing psychosis five-fold,
虽然听起来很诱人，但经常性地使用效力大于10%的大麻会使患精神疾病的风险增加5倍，

according to a study published this week by the Lancet. It also found that using less potent strains daily increased the risk three-fold.
《柳叶刀》期刊本周发表的一项研究说如是。该研究还发现每天食用低效力品种会将风险增加三倍。

Marta Di Forti, a clinical scientist at Kings College in London,
伦敦国王学院的临床科学家Marta Di Forti

and her colleagues looked at cannabis use among 901 European patients newly diagnosed with psychosis.
和她的同事对食用大麻并在近期被诊断患有精神疾病的901名欧洲病人进行观察。

A non-smoking control group was recruited from the general population.
他们从普通群体中招募了一支不抽烟的实验对照组。

The study adds substantial weight to the evidence linking cannabis to the onset of psychosis.
该研究给大麻和精神疾病发作之间的联系增添了实质性的重量级证据。

It also suggests that differences between varieties and how often they are used
该研究还表明各种变量之间的差别以及食用频率

could help explain why rates of psychosis among cannabis users vary across Europe.
可以帮助解释为什么在欧洲大麻使用者患精神疾病的比率各不相同。

Other factors, including genetic susceptibility, stress and injury, are also thought to be at work.
其他因素，包括遗传易感性、压力和受伤也被认为起到了作用。

Nonetheless, a growing body of evidence makes it likely that cannabis use is triggering mental-health problems in Europe.
尽管如此，有越来越多的证据证明在欧洲食用大麻会引起精神健康问题。

This may be particularly true in London and Amsterdam where high-THC weed is prevalent.
在伦敦和阿姆斯特丹这些高THC大麻盛行的国家尤为如此。

In London, 30% of new cases of psychosis in the study were estimated to be tied to strong cannabis—or an additional 13.8 cases per 100,000 people every year.
在该研究中，据估计伦敦30%的精神疾病新案例都和高效力大麻有关—或者说是每年每10万人中就有额外的13.8%例。

With the relaxation of cannabis laws in the United States and Canada,
随着美国和加拿大放松大麻法律政策，

many will wonder what this means for countries still developing their own policies.
很多人将猜想，对那些仍在发展本国政策的国家而言，这样做意味着什么。

Given the impracticality of removing high-potency strains from the illegal market,
考虑到不可能将高效力大麻品种移出非法市场，

the finds may support calls for legal, regulated sales of less harmful strains. It is difficult to know how this would affect public health.
这些发现或许可以支持提倡有害性更小的品种的合法管制性买卖。我们难以知道这将对公众健康有何影响。

However, as one scientist remarked recently, while laboratory animals are an expensive way of understanding the risks of cannabis use, "North Americans come free."
但正如一名科学家近期所说，虽然使用试验动物是理解食用大麻风险的一种昂贵方式，但是“北美人是免费的。”