All diagnoses in the MIDUS study were based on a phone interview that used the Composite International Diagnostic Interview Short Form scales (CIDI-SF; Kessler, Andrews, Mroczek, Ustun, & Wittchen, 1998). The CIDI-SF is a fully structured diagnostic interview that assesses the 12-month prevalence of mental disorders based on DSM-III-R criteria (American Psychiatric Association, 1987). The CIDI-SF scales were developed based on analysis of the Composite International Diagnostic Interview questions in the National Comorbidity Survey. The MIDUS study assesses for the symptoms of three disorders included in the internalizing spectrum: major depressive episode (MD), generalized anxiety disorder (GAD), and panic disorder (PD). The CIDI-SF MDD, GAD, and PD assessments have good total classification accuracy (percentage of respondents whose CIDI-SF classification is the same as their classification of the full CIDI), with percentages of 93%, 99%, and 98%, respectively (Kessler et al., 1998a) and, in turn, the full CIDI instrument has good agreement with clinical diagnoses (Kessler et al., 1998b; Wittchen, 1994).
