Hippocrates (470 - 410 BC) thought of the intense love as "greediness" created in the heart, and the stronger the intensity of love, the more a person becomes anxious and worried.  The increased anxiety causes sleeplessness and the blood will "burn" and become dark.  The "dark blood" spoils the person's thoughts causing "mental deficiency", which may lead to "insanity or madness."  This madness might cause a person in love or love addict to kill himself.  Also, the person in love might get together with his loved one and then might die because of excitement and happiness.  "You could observe", he said, "that this love addict, when he hears the name of the person he loves, his blood escapes and his color changes."

Galen (129 - 210 A.D.) later said about those who are in love: "Concern or worry causes the death of the heart while their "sadness" is considered a "heart disease" in itself.  He considered "falling in love" as a state of passionate liking combined with greediness or possessiveness.  He stated that "falling in love" is created by the "alnafs", which is the Arabic word for what we now refer to as the psyche.  "Alnafs" was thought by Galen to dwell inside the brain, the heart and the liver.