Vincent van Gogh's illness

I've just finished reading a fascinating book about van Gogh. There are numerous theories on the cause of his erratic behavior and suicide. A cursory search of the Web suggests that research done in the 1980s and 1990s holds the key to his illness--and it wasn't epilepsy, bi-polar disorder or schizophrenia. According to Dr. W.N. Arnold, Professor of Biochemistry at University of Kansas Medical Center and author of Vincent van Gogh: Chemicals, Crises, and Creativity, the illness of Vincent van Gogh was a congenital disease, acute intermittent porphyria (AIP). This debilitating genetic disease is characterized by sensitivity to light and other neurological abnormalities, including psychoses, hallucinations, convulsions and paralysis. The disease can be aggravated by poor nutrition, smoking and use of alcohol. There is substantial evidence that van Gogh drank absinthe and took excessive doses of camphor oil to relieve insomnia and pain. When he was institutionalized, his diet and habits improved and so did his symptoms. It's clear from his letters to his brother that his episodes of illness were extremely painful and something he dreaded, which may have been what led him to suicide. Another theory is that he was in the grip of an attack of AIP and accidentally shot himself, but there are no medical records to support either theory. There are some indications that his brother Theo and sister Wil may also have suffered from AIP. Dr. Arnold maintains, "He was wonderfully creative because of intelligence, talent, and hard work. He was a genius in spite of his illness - not because of it."