Under the Weather
September 10th, is World Suicide Prevention Day. While deaths from most causes have declined with economic development, suicide remains stubbornly high: even wealthy countries like Finland, France, and Japan retain among the highest rates in the world.
Yet if average income does not predict suicide prevalence, nonetheless we do find a curious correlation with the weather. Sunnier countries by and large have much lower suicide rates, on average, than gloomier ones (see figure, below).
Why this bizarre relationship between sunshine and self-preservation? The correlation could well be spurious: following the theories of French sociologist Émile Durkheim, perhaps sunnier countries have stronger family ties, or more conservative social norms. Alternatively, perhaps they are simply worse at collecting the data.
However, new psychological research does suggest reasons for a direct causal link. Around the world suicide rates tend to peak at the end of winter – in May in the northern hemisphere, and in September in the south. This suggests seasonality, rather than sunlight per se, may play a role. One theory is that long winters induce a depressive syndrome, which is followed by suicide attempts once people regain their springtime energies.