每天幾杯咖啡是否有助於緩解抑鬱大綱

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.

咖啡對健康有什麼影響，相關研究給出了五花八門的結論，讓人不知所措。有些說有益健康，另一些說有害健康——很難知道早上的那一杯咖啡到底是健康的靈藥還是慢性毒藥。

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.

在最近有關咖啡因的一項重要研究中，哈佛大學公共衛生學院的研究人員們發現，每天飲用2-4杯含咖啡因的咖啡與成年人中自殺風險的下降存在着相關性。

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.

該研究發表在《世界生物精神醫學雜誌》（The World Journal of Biological Psychiatry）上，這是一項對美國三個規模浩大的健康研究項目（共有43,599名男性和164,825名女性參加）進行的元分析。每四年，通過問卷形式對調查對象的咖啡因（來自茶、蘇打和可口可樂等飲料）、咖啡和脫咖啡因咖啡的攝入情況進行評估。全部三項研究中，從咖啡中攝入的咖啡因佔絕大多數，比例高達71%。

Causes of death were tracked during the study period by reviewing death certificates; 277 deaths were the result of suicide.

對於研究期間發生的死亡案例，研究人員會查看死亡證明書以追蹤死因；277例死亡源於自殺。

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.

分析顯示，每天飲用2-4杯咖啡（相當於約400毫克咖啡因）的成年人中，自殺的風險比飲用脫咖啡因咖啡或一杯以下含咖啡因咖啡的成年人低50%。每天飲用四杯以上咖啡並未進一步降低自殺風險。

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.

和所有具有相關性的結果一樣，值得注意的是該分析並未顯示出喝咖啡與自殺風險降低之間的因果關係，這項研究中也沒有任何證據顯示突然大幅提高你的咖啡因攝入量可緩解抑鬱症。同樣值得注意的是，本研究中調查的三項研究均是羣組研究，這表示這些研究是在幾年的時間內，對大型組羣的多個健康風險因素進行追蹤，在這種研究設計中，要對多個變量進行控制會出奇的困難。統計學家並不經常採用羣組研究的結果。

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.

話雖如此說，但這一發現背後的神經化學分析還是有些意義的。咖啡因的作用類似於大腦和身體其他部位中存在的一種稱爲腺苷的化學物質。腺苷由神經元產生，起制約平衡的作用；產生的腺苷越多，神經系統的活躍性越低，直至我們最終睡去並重新煥發活力。

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.

作用類似於腺苷，咖啡因阻隔了神經系統中的受體接收要降低能量消耗的信號。當這種情況發生時，大腦中的神經刺激物質——多巴胺和穀氨酸酯——的水平會上升，我們會體驗到喝下一大杯爪哇咖啡後對大腦產生的刺激效果。

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.

從這方面看，咖啡的作用可能像一種溫和的抗抑鬱劑，至少某種程度上是這樣。之前的研究也發現了類似的相關性，進一步表明咖啡——這一世界上被最頻繁攝取的精神活性物質——能夠幫助緩解抑鬱的可能性。

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，必須對這項研究審慎看待，該研究的結果決不是結論性的。鑑於羣組研究的缺陷，這一最新研究結果很可能是個“幻像”，在這一特定研究之外，此種相關性很可能並不成立。