The research team studied 65 men from around Cambridge. Thirty-five of them were active, addicted cocaine users. On average, they had used cocaine for 15 years in either powdered or freebase form. The rest of the men were matched in age to the addicts, but they had never used cocaine and didn't have any history of substance abuse. The majority of the cocaine users, on the other hand, were also dependent on other substances such as opiates, alcohol and cannabis. Ninety-one percent of the cocaine addicts were dependent on nicotine.