Definitions of secondary depression: effects on comorbidity and outcome in anxiety disorders.

The impact of different definitions of secondary depression on comorbidity and treatment outcome findings in anxiety disorder patients was examined by reviewing existing studies. Few data were found specifically on alternative definitions of secondary depression. However, other relevant findings yielded several conclusions: (a) different definitions of depression dramatically affect comorbidity findings, (b) widely divergent comorbidity findings are obtained in studies that use the same (temporal) definition of secondary depression, (c) few data exist on how different definitions of depression affect treatment outcome findings for anxiety disorders, and (d) some data show that patients' reports of whether or not their depressive symptoms temporally followed their anxiety symptoms are unreliable, suggesting that investigators who want to study secondary depression need to first determine that they have a reliable way to assess it.