Probands reporting serious drug dependence (defined as use of stimulants, cocaine, or opiates daily for more than three months or weekly for more than six months), and those who reported any history of intravenous substance use were excluded. Probands were excluded if, upon screening, they reported a current or past diagnosis of schizophrenia, bipolar disorder, or other psychiatric illness involving psychotic symptoms (those with depressive and anxiety disorders were accepted); a life-threatening illness; or an inability to speak and read English.
