Vincent van Gogh (1853–1890) endured frequent mental breakdowns and killed himself not long after painting the hallucinatory Starry Night. Hypotheses for his instability include bipolar disorder and poisoning from drinking absinthe. At The Illness of Vincent van Gogh, biochemist Wilfred Niels Arnold of the University of Kansas Medical Center in Kansas City lays out the case for an alternative diagnosis: acute intermittent porphyria. In this inherited metabolic disorder, noxious compounds accumulate because the body's production line for heme—a key component of hemoglobin—falters. With its embedded questions and lecture format, the site is geared toward medical students, but any curious visitor can gain insight into the painter's condition.