Study links rising temperatures to suicides ...59,300 suicides in India over the past three-and-a-half decades

G.S. Mudur, TT, New Delhi, July 31: A crop-damaging rise in temperatures may have catalysed about 59,300 suicides in India over the past three-and-a-half decades, a US-based economist said today after a study analysing weather trends and suicides.

The analysis by Tamma Carleton, a researcher at the University of California, Berkeley, has found that when the temperatures are above 20°C, a one degree rise on a single day during the monsoon season can on average be accompanied by about 70 suicides above the usual rate.

Her study is based on temperature and rainfall patterns and records of all suicides, not just farmer suicides, documented by India's National Crime Records Bureau. It has found that rises in temperatures during the main growing season from June through September has a "substantial influence" over suicide rates.

The latest bureau figures show that the annual suicide rate in India has risen by almost 16 per cent between 2004 and 2014, from about 113,000 in 2004 to 131,000 in 2014, although it has shown a slightly declining trend since 2010.

While earlier studies had tracked suicide trends, none had quantitatively examined the links between income-damaging changes in the weather and suicide rates. The new study has also used crop yield data from several decades to investigate the correlations between weather and suicides.

Temperature rises may have contributed to a cumulative total of 59,300 suicides across all states and all years since 1980, accounting for 6.8 per cent of the national upward trend in suicide rates over this period, she wrote in her paper. It was published today in the US journal, Proceedings of the National Academy of Sciences.

The study also found that an increase in the growing season rainfall by 1cm is associated with a decrease of about 8 suicides per million, lowering the suicide rate by 7 per cent on an average.

The results suggest that rainfall may help mitigate the suicide rate in India, presumably through its impact on agriculture.

"You can think of the relationship between climate and suicide like the rise in car accidents on rainy days," Carleton told The Telegraph.

"While rain increases the risk of accidents in general, any individual car accident is still dependent on the situation and choices made by the driver. We can measure the elevated risk of an accident on a rainy day on top of other factors such as driver error."

Mental health specialists say the study underscores the inherent occupational risks associated with farming in India and other developing countries, where farmers' income depends critically on the weather and crop procurement prices.

"Multiple factors may push an individual towards self-harm," said Vikram Patel, a psychiatrist based in India who is also a professor of global health at the Harvard Medical School. Easy access to the methods of suicide - pesticides, for example - is another factor.

Patel, who was not associated with the US study but has independently analysed suicide trends in India, said that while improved irrigation or crop insurance schemes can help protect farmers from weather uncertainties, there is also a need for interventions to help vulnerable individual farmers.

"We have to recognise that the vast majority of farmers face similar kinds of risks and uncertainties, but very few actually commit suicide," Patel said.

However, sections of crop and weather scientists say that while localised droughts and water shortages have contributed to farmers' distress, there is little evidence for significant crop failures from warming trends.