The interviewers were senior graduate students in their final part of training or experienced psychiatric nurses or psychologists, all trained and closely followed by professionals who had extensive previous experience with the instrument. Most of the PD interviews in wave 1 were conducted face to face, but for practical reasons, 231 (8.3%) were obtained by telephone. All wave 2 interviews were conducted by telephone. Each twin in a pair was interviewed by a different interviewer. Only few Axis I disorders (major depression, anxiety, and alcohol use) and 6 out of the 10 PDs were assessed in the second wave (paranoid, schizotypal, antisocial, borderline, avoidant, and obsessive-compulsive PDs).
