David Katerndahl, University of Texas Health Science Center at San Antonio
Chen-Pin Wang, University of Texas Health Science Center at San Antonio

Abstract: The purpose of this study was to explore the relationship between the dynamics of symptoms of anxiety and depression in primary care patients with newly-diagnosed major depressive episode (MDE), panic disorder, and neither disorder. Five adult patients presenting each with MDE, panic disorder, and neither disorder were recruited from two primary care clinics. Hourly self-assessments of levels of anxiety and depression were made for a 30-day period. Using differential structural equation modeling analysis, MDE and panic disorder differed from controls, but not from each other, in symptom levels, covariability, and effect on depression acceleration. Using state space grid analysis, attractors in controls were larger, more "influential", and more consistent. Patients with MDE had more total attractors but less consistent Week 1 attractors than patients with panic disorder or controls, suggesting more transient and less stable dynamics. This exploratory study suggests the importance of looking at covariability of anxiety and depression in mental illness.

Keywords: anxiety, depression, nonlinear dynamics, panic disorder, variability