Widespread opioid abuse is tied to a fall in the share of Americans working or looking for work, the head of the US central bank said on Thursday.
Federal Reserve Chair Janet Yellen said she was not sure if it was a cause of the decline or a symptom revealing more longstanding economic problems.
Technological changes and an ageing workforce also contributed, she said.
The Centers for Disease Control (CDC) estimate that prescription drug abuse costs $78.5bn (£61.5bn) annually.
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