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.
Harare is Zimbabwe's biggest city with a population of around 2 million; it's also the commercial capital of the country. The British founded the city in 1890 and called it Salisbury. When Zimbabwe gained independence in the early 1980's, the name was changed to Harare after a Shona chief, Neharawa.