Bipolar disorder, also known as manic-depressive illness, is an episodic but lifelong mental disorder. The first recognizable descriptions of mania and depression date back to the writings of Aretaeus of Cappadocia (a Greek physician who lived around 150–200 c.e.). The modern history of bipolar disorder begins in the midnineteenth century with the concept of folie circulaire (“circular insanity”) proposed by the French psychiatrist Jean-Pierre Falret. Later, it was defined by the work of the German psychiatrist Emil Kraepelin, around the beginning of the twentieth century.