In a research report, HSBC predicted that at the end of 2014, gross domestic product in the seven hardest-hit countries – Egypt, Tunisia, Libya, Syria, Jordan, Lebanon and Bahrain – would be 35% lower than it would have been if the 2011 uprisings had not happened.
"The combination of a severe fiscal deterioration, and a decline in government effectiveness, security and the rule of law will weigh heavily on policymakers' efforts, even to bring employment back to pre-revolution levels," it said.
HSBC forecast GDP growth in the Middle East and North Africa would slow to 4% this year, reviving only slightly to 4.2% next year, from 4.5% last year and 4.9% in 2011.
That forecast included big differences between the oil-rich Gulf, which has mostly boomed, and troubled countries in North Africa.
Egypt, for example, is expected to grow just 2.2% this year and 3% next year as it faces heavy pressures on its state budget and external accounts – growth rates which many analysts believe are too low to cut its unemployment.
Partly because the Arab Spring lifted oil prices and encouraged governments to boost spending on social welfare in order to buy peace, Gulf countries have mostly prospered since 2011. HSBC expects Saudi Arabia to grow 4.3% this year, falling slightly to 4% in 2014.
But the bank said the Arab Spring had also damaged the Gulf economies, by increasing their dependence on oil-fuelled government spending and deterring politically sensitive policy reforms.
"Only for the Gulf's wealthiest economies – Qatar, Abu Dhabi, Kuwait – does this approach look sustainable," HSBC said. Other countries with lower ratios of oil wealth to population may yet suffer as a result of the Arab Spring, it added.