Four years to the month since the global credit crisis began, European lenders remain dependent on central bank aid, plaguing markets and economies worldwide.

Emergency steps such as unlimited loans from the European Central Bank are keeping many banks in Greece, Portugal, Italy and Spain solvent and greasing the lending of others, while low interest rates and debt-buying are containing borrowing costs. Such aid is needed as concerns about slowing economic growth and sovereign debt prompt banks to curb lending, stockpile dollars and hoard cash in safe havens.

“I'm not sleeping at night,” said Charles Wyplosz, director of the Geneva-based International Center for Money and Banking Studies. “We have moved into a new phase of crisis.”