Beyond Mono-Method Symptom Assessment: Multimethod Extension of the Trilevel Model of Anxiety and Depression

The wide array of symptoms of and high comorbidity rates between unipolar depressive and anxiety-related disorders have raised questions about the relations among their symptoms. Factor analysis examines these relations, yet factor-analytic symptom-measurement models have relied on a single method of measurement and do not always replicate. We conceptually replicate and extend the trilevel model of anxiety and depression symptoms to encompass interviewer-rated symptoms. In the trilevel model, symptom-specific items load on three levels of factors: a narrow (or disorder-specific) factor, an intermediate-breadth factor, and a general-distress factor. The trilevel model fit well in this sample and fit better than comparison models that eliminated one of the three levels. Extension analysis successfully integrated interviewer-rating variables into the trilevel model—particularly for the broad and narrow levels. These results provide some support for the trilevel model and the use of interviewer ratings of symptoms. Research and treatment implications are discussed.