While financial markets have regained some composure since the start of the year, mounting global debt levels, sticky growth and the prospect of long-term negative rates are issues that are not going away anytime soon, the Bank for International Settlements has warned.

Concerns about growth in China and other emerging market economies and the health of some of the world's largest banks made for a very difficult start to 2016 for most investors, resulting in one of the worst stock market sell-offs since the financial crisis of 2008.