Hot temperatures are associated with
increased mortality. Predominantly, hot weather affects people with limited
adaptive responses, susceptible population including the elderly, those with
chronic diseases and socially deprived groups.
The same people
suffer an enhanced risk of suicide.
Despite
contrary results, most studies found an increase in the seasonal amplitude of
suicides in recent years, which would imply some effect of global warming on
the risk of suicide.
In Italy, the
variance accounted for by seasonal harmonics in the monthly distribution of
suicides decreased from 1974 to 1994, then began to increase progressively and
more evidently in 1999-2003, in coincidence with the repeated summer heat waves
recorded in Italy.
A recent study
carried out by Dr Antonio Preti in collaboration with Dr Gianluca Lentini and
Professor Maugeri Maurizio of the Applied General Physics Institute, Historical
Climatology Unit, University of Milan, Italy, found some evidence of an impact
of recent climate changes, brought about by global warming, on suicide
mortality in Italy.
The study,
which analyzed a total of 71,227 male suicides and 26,466 female suicides
identified in Italy from 1974 to 2003, found that increasing anomalies in
monthly average temperatures were associated to a higher mean monthly suicide
rate from May to August and, to a lower extent, in November and December among
males, with less consistent findings among females.
More suicides
in the months with a greater thermometric discomfort can be attributed, at
least partially, to the effect of global warming on survival after attempt:
extreme temperatures might increase the negative impact of body self-harm on
the chance of surviving after a suicide attempt.
Another issue
of concern is the positive relationship between temperature and aggression: many studies indicate that aggressiveness is linked
to suicidal behaviour, both directly and indirectly, via the common dimension
of impulsivity. Consequently, hot temperatures might trigger impulsive
suicides, thus increasing mortality among people with severe mental disorders.
Interventions
aimed at reducing anthropogenic effects on climate, such as reducing air pollution
and improving energy allocation, are strategic; however, short-term
interventions can be effective as well, such as improving the buffering
capacity through technology (air conditioning) and implementing a weather-watch
warning system.
References:
Preti A,
Lentini G, Maugeri M
Global warming
possibly linked to an enhanced risk of suicide: Data from Italy, 1974-2003.
Journal of
Affective Disorders, 2007; 102: 19-25.
Rocchi MBL,
Sisti D, Cascio MT, Preti A
Seasonality and
suicide in Italy: Amplitude is positively related to suicide rates. Journal of
Affective Disorders, 2007; 100: 129-136.
Contacts:
Dr Antonio
Preti
SchizophreniaProject
e-mail: apreti@tin.it