Over the next few months in the northern hemisphere, suicides are likely to become more common. Why?

在北半球接下来的几个月里，自杀现象可能会更加普遍，这是为什么呢？

Studies dating back to the 1800s have found that suicides peak in the spring and are lowest in winter.

19世纪的研究发现，自杀率在春季达到顶峰，在冬季最低。

"If we take winter as a baseline, then there's a 20-60% higher suicide rate during spring," says Fotis Papadopoulos, a professor of psychiatry¹ at Uppsala University in Sweden, who has been studying the association.

瑞典乌普萨拉大学精神病学教授福蒂斯·帕帕多普洛斯表示：“如果我们以冬季的自杀率为基准，那么春季的自杀率将高出20-60％。”

This seems rather counterintuitive considering that darker days are linked to low mood. How could this be?

这似乎是相当违反我们的认知的，我们通常认为萎靡的心情与较暗的天气有关。那这到底是怎么一回事呢？

One possibility is that this is a result of changing levels of serotonin – a neurotransmitter that regulates mood – within the brain.

一个可能的原因就是，这是血清素水平升高的结果，即5-羟色胺（一种在大脑内调节心境的神经递质）。

Studies have found that serotonin levels in the blood are higher during the summer than the winter, and that there's a positive correlation² between serotonin synthesis and the hours of sunshine on the day that a blood sample is taken.

研究发现，夏季血液中5-羟色胺水平高于冬季，血清素合成与摄取当天阳光时间呈正相关。

There's also a further connection, in that selective serotonin reuptake inhibitor (SSRI) antidepressants, which boost serotonin, have been linked to risk of suicide in a small number of patients.

还有一个更进一步的联系：在选择性5-羟色胺再摄取抑制剂（SSRI）抗抑郁药中，其促进5-羟色胺与少数患者的自杀风险相关。

"We know that when we treat patients with antidepressants it can take at least three or four weeks to raise their mood," says Papadopoulos. "During this time, some people become more physically³ active or agitated⁴, which could potentially make them more likely to act on their thoughts. Maybe sunshine acts in a similar way in a minority of people."

帕帕多普洛斯说道：“我们知道，当我们用抗抑郁药治疗患者时，可能需要至少三到四个星期来使他们恢复好心情。在这段时间里，有些人变得更加活跃或激动，这可能会使他们更有可能采取行动。或许阳光对一部分人起到的是同样的作用。”