Public debt can impact economic growth in European countries. High debt levels can be harmful, but some debt can help growth if used for public investments. A study of 33 European countries found a "U inverted" relationship between debt and growth, with a threshold of 94% of GDP. Beyond this threshold, high debt can lead to lower growth due to higher interest rates and budget cuts. Developing countries have a lower threshold than developed ones due to less credibility and reliance on external funding.