https://doi.org/10.1177/2167702617745640 Clinical Psychological Science 1–10 © The Author(s) 2017 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/2167702617745640 www.psychologicalscience.org/CPS Empirical Article Anxiety and depression are two common and highly comorbid conditions (Brown, Campbell, Lehman, Grisham, & Mancill, 2001; Cummings, Caporino, & Kendall, 2014; Curtiss & Klemanski, 2015), in part due to shared psychological and biological vulnerabilities (Brown & Barlow, 2009; Hettema, Neale, Myers, Prescott, & Kendler, 2006). In addition, functional impairment is high among those with anxiety disorders (Cramer, Torgersen, & Kringlen, 2005; Mendlowicz & Stein, 2000; Olatunji, Cisler, & Tolin, 2007; Rapaport, Clary, Fayyad, & Endicott, 2005) and depression (Greenberg, Fournier, Sisitsky, Pike, & Kessler, 2015; Judd et al., 2000; Marcus & Olfson, 2010; World Health Organization, 2005). Both disorders tend to wax and wane over time, but the long- term effects of these problems on functional impairment are not well understood. Clarifying this issue might aid treatments for patients with comorbid conditions. In a study examining the 40-year course of anxiety and depression, depression was associated with greater chronicity and recurrence than anxiety (Murphy, 1986, 1990). Another study investigating the long-term con- sequences of these conditions revealed that pure forms of depression and anxiety remained stable over a period of 25 years (Hagnell & Grasbeck, 1990). In the Zurich Cohort Study, the comorbid presentations of depression and anxiety evidenced strong temporal stability, with depression exhibiting greater stability than anxiety over 15 years (Merikangas et al., 2003). Some studies suggest that depression temporally precedes anxiety as often as anxiety precedes depression, indicating that these conditions are mutually reinforcing across time and are potentially reflective of a broader, self-sustaining sys- tem of psychopathology (Moffitt et al., 2007). 745640CPX XX X 10.1177/2167702617745640Curtiss et al.Network Stability of Impairment of Anxiety and Depression research-article 2017 Corresponding Author: Stefan G. Hofmann, Department of Psychological and Brain Sciences, Boston University, 648 Beacon St., 6th Floor, Boston, MA 02215 E-mail: shofmann@bu.edu Longitudinal Network Stability of the Functional Impairment of Anxiety and Depression Joshua Curtiss 1 , Masaya Ito 2 , Yoshitake Takebayashi 3 , and Stefan G. Hofmann 1 1 Department of Psychological and Brain Sciences, Boston University; 2 National Center of Neurology and Psychiatry, Tokyo, Japan; and 3 Fukushima Medical University Abstract Anxiety and depression are comorbid conditions with significant functional impairment. This study examines the temporal changes in the network structure of the functional impairment associated with anxiety and depression. A clinical sample (N = 1,667) of individuals from Japan completed a battery of self-report instruments to assess the degree and level of impairment of anxiety and depression. The network structure was estimated at two time points using partial correlation coefficients and the glasso regularization procedure. Several permutation tests were conducted to examine network changes over time. Global and individual features of the network were stable across time. Furthermore, depression was more central than anxiety at both time points. Results should be interpreted in light of cultural factors involving the Japanese sample. These results underscore the temporal stability of the functional impairment of anxiety and depression as well as the importance of depression in the overall comorbid network. Keywords network dynamic, anxiety, depression, impairment Received 6/24/17; Revision accepted 10/29/17