Aretaeus of Cappadocia describes Bi-Polar disorder in 150 A.D.

δοκέει τεδέ μοι μανίης τε ἔμμεναι ἀρχὴ καὶ μέρος ἡ μελαγχολίη . 

 ‘‘ . . . I think that melancholia is the beginning and a part of mania . . "

 Aretaeus, On the Causes and Symptoms of Chronic Diseases Book 1 Chapter 5.

The first physician to describe manic-depressive illness as one entity---one disease with two opposite constellations of symptoms was Aretaeus. He was born in Cappadocia during the Roman domination of Asia Minor. Few details are known about his life, but it is believed he studied in Alexandria and practiced medicine in Rome around the second century AD. After his death he was forgotten until rediscovered during the Renaissance, when a Latin translation of his eight-volume treatise appeared in Venice and two years later the original Greek text was published in Paris. 

Here is just a little of what he wrote about Bi-Polar disorder in  about 150 AD:

 ‘‘ . . . I think that melancholia is the beginning and a part of mania . .  The development of a mania is really a worsening of the disease (melancholia) rather than a change into another disease. . . In most of them (melancholics) the sadness became better after various lengths of time and changed into happiness; the patients then developed a mania."

I compared the current criteria for diagnosing mania and depression with a wealth of diagnostic statements in the original Greek version of  Aretaeus, On the Causes and Symptoms of Chronic Diseases Book 1 Chapter 5. Aretaeus gets a 7/13 or so on mania. I’m giving him 6/10 on the depression side. So mania and depression combined, Aretaeus gets 13/23 of the same criteria we use today, which is not bad at all.

Aretaeus speculated that the pathogenesis of mental illness was biological, and the recommended treatment was mainly biological.