"Black bile" was a concept first conceived by the Greek physician Hippocrates, who lived between 460 and 370 Before Common Era (BCE). An overabundance of the substance in the human system was believed to result in severe depression. Balancing levels of black bile with other humors in the body was supposed to cure the condition. Other diseases associated with impaired functioning, such as sexual dysfunction and difficulty in breathing, were also believed to result from black bile imbalances. Medical and psychological research has since debunked the theory, determining neurological malfunction as the primary physiological cause of depression.
Hippocrates identified this bile as one of the four essential humors in the human body, along with yellow bile, blood, and phlegm. An imbalance in any of these humors, through excess or deficit, was believed to lead to the various diseases the system could suffer. The four fluids were also believed to have an effect on an individual's mood; an excess of phlegm, for example, supposedly made individuals emotionally unresponsive.
Each of the fluids was associated with an element of nature, and the maladies caused by their imbalances were indicative of this quality. An overabundance of yellow bile, for example, was connected to excessive fires in the body, leading to "warm" conditions such as fever. Black bile was representative of Earth and identified as the cause of diseases that added "weight" to the body. This included fatigue, lethargy, and heavy drops in mood. The word "melancholia," a state of mind later associated with depression, takes its name from the Latin "melan" and "chole," literally meaning "black bile."
Diseases, according to humorism, were caused by dysfunction in the organs that served as reservoirs for these bodily fluids. In the case of black bile, mood and fatigue disorders were thought to originate from the spleen. Ancient Greek doctors believed the humor would overflow into the stomach and the rest of the digestive tract, causing a host of gastrointestinal disorders. The bile that made its way into the patients' skeletal system could harden or weigh down the bone, resulting in conditions like rheumatoid arthritis.
Treatment often began by attempting to balance the humors from outside. This generally entailed counteracting the disease with appropriate levels of physical activity and controlling the patient's body temperature; certain diets were also thought to contribute to humor readjustment. If these first steps were proven ineffective, treatment moved on to what was thought to be direct control over humor levels. These methods included bloodletting in affected areas and poison ingestion to induce vomiting.