Money woes can not only leave your bank balance impoverished, but also you brain, scientists have warned.
Finding it hard to make ends meet can expends so much mental energy it can reduce your ability to think, the new study has claimed.
Financial worries can tax the brain so much they create a "cognitive deficit" equivalent to a 13-point loss in IQ – on the same scale as losing an entire night's sleep.
The problem is distinct from the effects of stress and is sparked by having too many things to worry about – resulting in your ability to think clearly becoming limited, the scientists claim.
Someone overwhelmed with worries about rent, feeding and clothing children, and paying household bills can suffer a genuine mental handicap, the research shows.
This in turn may lead to poor decisions, such as racking up debt, creating even more difficulties in a vicious cycle.
Economics professor Sendhil Mullainathan, from Harvard University in the US, said: "Our results suggest that when you're poor, money is not the only thing in short supply. Cognitive capacity is also stretched thin.
"That's not to say that poor people are less intelligent than others. What we show is that the same person experiencing poverty suffers a cognitive deficit, as opposed to when they're not experiencing poverty.
Prof Mullanathan's team carried out a series of experiments in the US and India to highlight the mental cost of poverty, making randomly chosen people ponder how they would solve hypothetical financial problems.
At the same time, the volunteers had to undergo simple computer tests of IQ and mental performance.
They were split into "poor" and "rich" groups based on their income which ranged from 20,000 dollars per year to around 70,000 dollars.
The results, reported in the journal Science, show that when the financial problems were not too severe, both groups performed equally well in the tests.
But when they were forced to consider difficult, costly problems, people with lower incomes had significantly worse scores.
In fact, the effect was so strong that for those generally preoccupied with money, merely thinking about a tricky financial problem led to a massive 13-point dip in IQ.
The impact of poverty on mental capacity reflects a more general phenomenon related to scarcity, say the researchers.
Lacking something, whether it be money, time, social ties or even calories, puts a strain on the brain, they said.
Professor Eldar Shafir, another member of the Princeton team, said poverty has a long-lasting mental impact.
"When you're poor you can't say, 'I've had enough, I'm not going to be poor any more, or 'forget it, I just won't give my kids dinner, or pay rent this month," he said.
"Poverty imposes a much stronger load that's not optional and in very many cases is long lasting. It's not a choice you're making, you're just reduced to a few options. This is not something you see with many other types of scarcity."
Services to the poor should take account of the mental effect of poverty, for instance by providing simpler forms and making it easier to seek assistance, said Prof Shafir.
"The poor, who our research suggests are bound to make more mistakes and pay more dearly for errors, inhabit contexts often not designed to help."