Who believed that imbalances in the four essential fluids of the body could lead to mental illness?

Hippocrates, often referred to as the "Father of Medicine," proposed the theory of humoralism, which posits that human health and temperament are influenced by four bodily fluids: blood, phlegm, yellow bile, and black bile. He believed that an imbalance in these fluids could not only affect physical health but also lead to various mental illnesses. This understanding laid the groundwork for the idea that physical conditions can heavily influence mental states, underscoring the connections between body and mind that continue to be explored in modern psychology and medicine. Through his clinical observations and philosophical inquiries, Hippocrates significantly contributed to the early understanding of mental health within a biological framework.