Their depression or insanity fostered their creativity. Perhaps every artist has some sort of depression.
Thesis: The most successful or famous artists in history are not always as happy as they portray themselves; in fact, their depression may foster creativity.
Vincent van Gogh's depression caused him to do many disturbing things to his friend Paul Gaugin. Once he chased after Paul with a razor blade. When Paul turned around Vincent ran home. The next morning Paul found Vincent bleeding profusely from where he had almost cut his whole ear off. Vincent gave the piece of the ear to his friend Rachel, telling her to guard it carefully (Moore 944-947).
It is believed Vincent cut his ear off because he was tormented by voices, and was having hallucinations. In 1888 he was diagnosed with some sort of epilepsy which caused him to have nervous attacks. Four months later he decided to commit himself to the St. Paul-de-Mausole Asylum for awhile. However his nervous attacks and depression did not stop. In 1890, he decided he was incurable and attempted suicide (Moore 944-947).