All subjects were interviewed using the Semi-Structured Assessment for Drug Dependence and Alcoholism, which has been shown to yield reliable substance dependence diagnoses.21,26 Subjects with a primary diagnosis of a major psychotic illness (schizophrenia or schizoaffective disorder) were excluded. A diagnosis of CD was established if the subject met 3 or more of the 7 DSM-IV criteria during a 12-month period. The interrater reliability of the Semi-Structured Assessment for Drug Dependence and Alcoholism diagnosis of CD was previously shown to be κ=0.83.21 Subjects who gave an affirmative answer to the question, “Have you ever had a paranoid experience when you were using cocaine?” were diagnosed as being affected by CIP. The overall reliability of CIP diagnosis was previously shown to be excellent (κ=0.87).21 Controls did not use cocaine, but individuals who had dependence on other substances were included. Probands were excluded from further study if they had a diagnosed major psychotic illness (eg, schizophrenia or schizoaffective disorder). Subjects who had missing responses to items on the Semi-Structured Assessment for Drug Dependence and Alcoholism that were required for the determination of CD or CIP status were also excluded.
