a downward spiral的用法和样例：
- This caused a downward spiral into depression.
- This was a downward spiral, because it meant buried ones had room to resurface.
- Jane had experienced a downward spiral by the time I interviewed her.
- A lot of times these answers were wrapped up in a totally haywire drama of fast-paced teens and a downward spiral.
- And secondly, at the zero bound there is some possibility of a downward spiral of worsening deflation.