There may be no single cause of bipolar disorder (aka manic depression). Instead, research indicates the causes of bipolar disorder are probably a combination of biochemical, genetic and environmental factors that may trigger and perpetuate the chemical imbalances in the brain.
Net worth: $829 million. Telecommunications mogul Strive Masiyiwa is widely regarded as the richest man in Zimbabwe and is one of the richest men in Africa with a net worth of more than US$800 million.
In 2007 a millionaire in Zimbabwe could have been extremely poor. At the end of 2017, there were estimated to be just over 15 million US$ millionaires or high-net-worth individual (HNWIs) in the world.