We considered three explanations. First, compared with DSM-IV, DSM-5 field trial cases could have been more complex because of comorbidity that reduced reliability. This appears unlikely, however, because the DSM-IV studies did not exclude comorbid cases, and they recruited participants from settings in which comorbidity was common. Second, DSM-IV kappas could have been inflated because multisite studies did not adjust for data pooled across sites. The reanalysis of data from one of the studies (3) after making this adjustment (4) suggests that this is also unlikely. After pooling data from sites with more than 50 patients, the unadjusted and adjusted kappas did not differ dramatically (Table 1).