"drain confidence" is correct and usable in written English.
You can use it to refer to a situation where someone or something is causing a depletion of someone's self-confidence. For example, "The constant criticism from her supervisor began to drain her confidence."
But it helped drain confidence, the most important asset in banking.
"If Tuesday's summit achieves nothing, if the convening power of the American president on Tuesday doesn't deliver, it will further drain confidence that the international system gets it".
A big rate cut, he said, is more likely to drain confidence than perk it up, if "it is interpreted as a signal that the central bank has a more pessimistic assessment of the economy than market participants".
The market is debating whether the industrial export and technology cycles will fall prey to the acidic politics that daily drain confidence in the country's ability to navigate events.
This is all adding to the worries over the large current account deficit and draining confidence from its currency as investors fret about the ability of the Indian government to manage when the era of cheap money ends.
But we were worried a report which said that the academy was inadequate would be used to drain the confidence of our students and parents.
Occasionally it happens that results against certain sides drain boardroom confidence and indicate that it might be time for a manager to go, though, that usually only comes into effect because the side in question is perceived to be struggling itself and therefore easy to beat.
The early goal scored by Luxembourg seemed to drain any confidence that had built up as a result of the impressive first-half performance.
In this context, a prolonged federal shutdown would drain Americans' confidence in their government, hobbling spending, borrowing and investment -- and pushing the economy toward recession, said Mark Zandi, chief economist of Moody's Analytics.
MIAMI — Caught in the baseball vortex that had vaporized their offense and drained their confidence, the Mets searched for an escape route before Tuesday's game at Marlins Park.
