每天几杯咖啡是否有助于缓解抑郁

Following the research on the health effects of caffeine is dizzying. Positive in some cases, negative in others – it’s hard to know whether that morning cup of joe is a health elixir or slow-acting poison.
咖啡对健康有什么影响，相关研究给出了五花八门的结论，让人不知所措。有些说有益健康，另一些说有害健康——很难知道早上的那一杯咖啡到底是健康的灵药还是慢性毒药。

In the latest major study on caffeine’s effects, researchers from the Harvard School of Public Health found a correlation between drinking 2-4 cups of caffeinated coffee each day and lower suicide risk among adults.
在最近有关咖啡因的一项重要研究中，哈佛大学公共卫生学院的研究人员们发现，每天饮用2-4杯含咖啡因的咖啡与成年人中自杀风险的下降存在着相关性。

The study, published in The World Journal of Biological Psychiatry, was a meta-review of three extensive U.S. health studies that included a total of 43, 599 men and 164, 825 women. Consumption of caffeine (from tea, soda and chocolate), coffee and decaffeinated coffee was evaluated among study participants every four years via questionnaire. Across all three studies, coffee accounted for the majority of caffeine consumed at 71% of the total.
该研究发表在《世界生物精神医学杂志》（The World Journal of Biological Psychiatry）上，这是一项对美国三个规模浩大的健康研究项目（共有43,599名男性和164,825名女性参加）进行的元分析。每四年，通过问卷形式对调查对象的咖啡因（来自茶、苏打和可口可乐等饮料）、咖啡和脱咖啡因咖啡的摄入情况进行评估。全部三项研究中，从咖啡中摄入的咖啡因占绝大多数，比例高达71%。

Causes of death were tracked during the study period by reviewing death certificates; 277 deaths were the result of suicide.
对于研究期间发生的死亡案例，研究人员会查看死亡证明书以追踪死因；277例死亡源于自杀。

The analysis showed that the risk of suicide among adults drinking 2-4 cups of coffee (the equivalent of about 400 mg of caffeine) a day was 50% less than the risk for adults who drank decaffeinated coffee or one cup or less of caffeinated coffee. Drinking more than 4 cups of coffee didn’t drop the suicide risk lower.
分析显示，每天饮用2-4杯咖啡（相当于约400毫克咖啡因）的成年人中，自杀的风险比饮用脱咖啡因咖啡或一杯以下含咖啡因咖啡的成年人低50%。每天饮用四杯以上咖啡并未进一步降低自杀风险。

As with all correlative results, it’s worth noting that this analysis does not show causation between drinking coffee and lower suicide risk, and there’s nothing in this study to suggest that suddenly bumping up your caffeine intake will curb depression. It’s also worth noting that the three studies examined in this one were cohort studies, meaning they tracked multiple health risk factors across large groups over the course of several years, and it’s notoriously difficult to control for variables with this study design. Cohort study results aren’t very popular with statisticians.
和所有具有相关性的结果一样，值得注意的是该分析并未显示出喝咖啡与自杀风险降低之间的因果关系，这项研究中也没有任何证据显示突然大幅提高你的咖啡因摄入量可缓解抑郁症。同样值得注意的是，本研究中调查的三项研究均是群组研究，这表示这些研究是在几年的时间内，对大型组群的多个健康风险因素进行追踪，在这种研究设计中，要对多个变量进行控制会出奇的困难。统计学家并不经常采用群组研究的结果。

Having said that, the neurochemistry behind the finding makes sense. As discussed in a previous article, caffeine acts as an expert mimic of a chemical called adenosine in the brain and other parts of the body. Adenosine is a sort of checks-and-balances chemical produced by neurons as they fire throughout the day; the more adenosine is produced, the more the nervous system ratchets down activity, until we eventually fall asleep and reboot the process.
话虽如此说，但这一发现背后的神经化学分析还是有些意义的。咖啡因的作用类似于大脑和身体其他部位中存在的一种称为腺苷的化学物质。腺苷由神经元产生，起制约平衡的作用；产生的腺苷越多，神经系统的活跃性越低，直至我们最终睡去并重新焕发活力。

By mimicking adenosine, caffeine blocks receptors in the nervous system from receiving the signals to decrease energy expenditure. When that happens, levels of the brain’s homegrown neuro-stimulants—dopamine and glutamate—increase, and we experience the brain stimulating effects associated with drinking a big cup of java.
作用类似于腺苷，咖啡因阻隔了神经系统中的受体接收要降低能量消耗的信号。当这种情况发生时，大脑中的神经刺激物质——多巴胺和谷氨酸酯——的水平会上升，我们会体验到喝下一大杯爪哇咖啡后对大脑产生的刺激效果。

Seen this way, coffee may act as a mild antidepressant — at least to an extent. Previous research has found similar correlations reinforcing the possibility that coffee–the most frequently ingested psychoactive substance in the world–can help alleviate depression.
从这方面看，咖啡的作用可能像一种温和的抗抑郁剂，至少某种程度上是这样。之前的研究也发现了类似的相关性，进一步表明咖啡——这一世界上被最频繁摄取的精神活性物质——能够帮助缓解抑郁的可能性。

All of this research, however, should be taken with an enormous caveat that the findings are anything but conclusive. And given the drawbacks of cohort studies, it’s possible that the latest study results are a “mirage” that wouldn’t hold true outside of this particular correlative fishbowl.
然而，必须对这项研究审慎看待，该研究的结果决不是结论性的。鉴于群组研究的缺陷，这一最新研究结果很可能是个“幻像”，在这一特定研究之外，此种相关性很可能并不成立。