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A legend, often mentioned together with the "holes in the brain" myth, is that MDMA causes Parkinson's disease. This was partially based on an animal study that found neurotoxicity to dopaminergic neurons after administering the drug to monkeys. However, the study was eventually retracted by the researchers because they had accidentally given methamphetamine instead of MDMA to the animals. Ironically, it is now being investigated as a possible treatment for Parkinson's disease.