Symptom comorbidity in anxiety and depressive disorders.

: The ability of the Hamilton Rating Scale for Anxiety, the Hamilton Rating Scale for Depression, and 50 items from the self-rated Hopkins Symptom Checklist to discriminate generalized anxiety disorder from major depressive disorder was examined for over 3,000 patients entering studies in three drug development projects at Bristol-Myers Squibb Company. Discriminant analysis models using stepwise procedures were developed for each scale separately, combining both Hamilton scales, and combining all three scales. The statistical model using both Hamilton scales produced the best discrimination. Items from the Hopkins Symptom Checklist scale did not improve the ability to discriminate patients by diagnosis correctly. The generalizability was tested by applying the discriminant models to new data sets or subsets of the data sets used in the model-building process. Correct classification rates for differentiating the two disorders ranged from 87-99% for the final model.