Some people may be more likely to become drug addicts because their brains function in a certain way, according to new research from the University of Maryland.

Dr. Lynn Oswald and her colleagues used PET scans (positron emission tomography) to research neurobiological mechanisms that may predispose a person to drug addiction. For example, increased impulsivity and high stress levels affect the dopamine system of the brain. Preexisting differences in dopamine function could predispose people not only to addiction, but also to Tourette's syndrome, schizophrenia, and attention deficit disorder.

"Addiction is a brain disease because differences in the way our brains function make some people more likely to become addicted to drugs than others -- just as differences in our bodies make some people more likely to develop cancer or heart disease," Dr. Oswald said.