As if debt, food and water shortages aren't enough for the poor to worry about, new research shows that poverty and the all-consuming fretting that comes with it require so much mental energy that the poor have little brain power left to devote to other areas of life.
The mental strain could be costing poor people up to 13 IQ (intelligence quotient) points, and means they are more likely to make mistakes and bad decisions that amplify and perpetuate their financial woes, according to the findings of an international study published last week.
"Our results suggest that, when you are poor, money is not the only thing in short supply. Cognitive capacity is also stretched thin," said Harvard economist Sendhil Mullainathan.
Researchers from Harvard, Princeton and other universities in the US and from Britain's University of Warwick found that pressing financial worries had an immediate impact on poor people's ability to perform well in cognitive and logic tests.
Far from signalling that poor people are stupid, the results suggest those living on a tight budget have their effective brain power, or what researchers called "mental bandwidth", dramatically limited by the stress of making ends meet.
On average, someone weighed down by money woes showed a drop in cognitive function in one part of the study that was comparable to a 13-point dip in IQ, and similar to the performance deficit expected from someone who has missed a whole night's sleep.
"Previous views of poverty have blamed (it) on personal failings, on an environment not conducive to success," said Jiaying Zhao, assistant professor of psychology at the University of British Columbia in Canada.
"We are arguing that the lack of financial resources itself can lead to impaired cognitive function," she said.
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