Cocaine, as they say, is a hell of a drug. It affects three of the neurotransmitters in our brains that make us feel fantastic -- dopamine, serotonin and norepinephrine -- and tolerance for the stuff doesn't seem to dissipate even months after quitting. (It's also expensive and bad for you.) Today, new research published in Translational Psychiatry adds another bizarre facet to one of the world's most popular drugs: The cocaine addicts in your life have unusual deposits of iron in their brains.