Increased Risk Of Suicide In Hot Weather, UK

August 17, 2007 – 11:05 pm | posted in Psychology / Psychiatry

There is an increased risk of suicide during hot weather, a new study has discovered.

Seasonal fluctuation in suicide has been observed in many populations. High temperature may contribute to this, but the effect of short-term temperature changes has not been studied.

Published in the August 2007 issue of the British Journal of Psychiatry, this study set out to assess the relationship between daily temperature and daily suicide counts in England and Wales between January 1993 and December 2003.

It also explored whether heat waves are linked to increased mortality from suicide.

During the period studied there were 53,623 suicides, with an average of 13.3 per day. Three-quarters of all suicides were by men, and this proportion remained constant over the study period. The proportion of violent suicides increased during the period studied.

The highest daily suicide count was recorded for January 1st. There was good evidence that suicides decreased during the Christmas period when compared with the rest of the year.

The largest number of suicides took place on Mondays, with numbers declining as the week wore on. A similar pattern was found for violent and non-violent suicides.

The researchers did not find a spring or summer peak in suicide. However, above 18 degrees C, each one degree C increase in average temperature was associated with a 3.8% rise in all suicides and a 5.0% rise in violent suicide.

Suicide increased by 46.9% during the 1995 heat wave, although there was no change in suicide rates during the 2003 heat wave.

There was no clear difference in the relative risk of high temperature on male or female suicide.

The researchers comment that although the majority of European studies have shown a spring or summer peak in suicide, studies from the recent past in the UK have not. One study investigating seasonality and suicide in 28 countries found that those with high levels of industrialisation, and low numbers involved in agricultural work, showed the least seasonality.

The relationship between suicide and average temperature shows a similar threshold to that of total mortality and temperature, which has been estimated to occur at about 19 degrees C.

This study is the first to show that death from suicide has been shown to be contributing to the known short-term increase in all-cause mortality at higher temperatures.

It is not infrequent for the average temperature in England to be above 18 degrees C, with such values being recorded on 222 days over the 11-year period studied. Real additional suicides, rather than suicides being ‘brought forward’, probably occur when temperatures are high, say the researchers.

The surprising finding that suicides increased during the 1995 heat wave but not during the 2003 heat wave may be explained by the fact that there were 2 periods of very hot weather in 2003, in mid-July and in August. The later heat wave in August may have resulted in fewer deaths through adaptation to higher temperatures among vulnerable people.

There are 3 mechanisms by which higher temperatures could cause suicides - sociological, biological and psychological, which the researchers explore.

The effect of high temperatures on suicide counts will probably become more important as global warming continues. If a consistent association between short-term high temperatures and suicide is identified, further attention needs to be paid to the mechanisms that underlie this effect.

References:

Relationship between daily suicide counts and temperature in England and Wales, L. A. Page, S. Hajat and R. S. Kovats, Br J Psychiatry 2007 191 (2)

http://www.rcpsych.ac.uk

ShareThis