Bipolar disorder is perhaps one of the oldest known illnesses. Research reveals some mention of the symptoms in early medical records. It was first noticed as far back as the second century. Aretaeus of Cappadocia (a city in ancient Turkey) first recognized some symptoms of mania and depression, and felt they could be linked to each other. His findings went unnoticed and unsubstantiated until 1650, when a scientist named Richard Burton wrote a book, The Anatomy of Melancholia, which focused specifically on depression. His findings are still used today by many in the mental health field, and he is credited with being the father of depression as a mental illness. 

Jules Falret coined term "folie circulaire" (circular insanity) in 1854, and established a link between depression and suicide. His work led to the term bipolar disorder, as he was able to find a distinction between moments of depression and heightened moods. He recognized this to be different from simple depression, and finally in 1875 his recorded findings were termed Manic-Depressive Psychosis, a psychiatric disorder. Another lesser-known fact attributed to Falret is that he found the disease seemed to be found in certain families thus recognizing very early that there was a genetic link.

Francois Baillarger believed there was a major distinction between bipolar disorder and schizophrenia. He characterized the depressive phase of the disease. It was this achievement that allowed bipolar disorder to receive its own classification from other mental disorders of the time.  In 1913, Emil Krapelin established the term manic-depressive, with an exhaustive study surrounding the effects of depression and a small portion about the manic state. Within fifteen years, this approach to mental illness was fully accepted and became the prevailing theory of the early 1930’s.