Abu Zayd Ahmed ibn Sahl Balkhi (Persian: ابو زید احمد بن سهل بلخی) was a Persian Muslim polymath: a geographer, mathematician, physician, psychologist and scientist. Born in 850 CE in Shamistiyan, in the province of Balkh, Greater Khorasan, he was a disciple of al-Kindi. He also founded the "Balkhī school" of terrestrial mapping in Baghdad. Al-Balkhi is believed to have been the first to diagnose that mental illness can have psychological and physiological causes and he was the first to typify four types of emotional disorders: fear and anxiety; anger and aggression; sadness and depression; and obsessions. Source: Wikipedia (en)