1. Identifying the Core Symptoms of Bulimia Nervosa and Associated Anxiety and Depression
Cheri Levinson, Stephanie Zerwas, Benjamin CALEBS, Kelsie Forbush, Hunna Watson, Hans Kordy, Sara Hofmeier, Michele Levine, Benjamin Zimmer, Markus MOESSNER, Christine Peat, Cristin Runfola, Marsha Marcus, Cynthia Bulik

2. What is at the CORE OF BULIMIA NERVOSA?
Bulimia nervosa (BN) is characterized by symptoms of:
binge eating and compensatory behavior
overevaluation of weight and shape
BN symptoms often co-occur with symptoms of anxiety and depression
Which specific BN symptoms maintain BN psychopathology?
How are these symptoms associated with symptoms of depression and anxiety?
Fairburn, Cooper, & Shafran, 2003; Palister & Waller, 2008

3. Models of Psychopathology
Latent variable theory often used to describe why mental disorders develop & persist
Symptoms arise from a common cause
BN is the cause that leads to each of these common symptoms. BN
Fear of weight gain
Binge eating
Purging
Avoidance of food
Bollen, 2002; Borsboom et al., 2016; Clark & Watson, 1991; Eaton, 2015; Haslam, Holland, & Kuppens, 2012

4. Network theory proposes that symptoms of disorders cause each other
Symptoms are part of a dynamic network which can produce, sustain, and underlie mental disorders
These interact with each other to strengthen (or weaken) the disorder
Fear of Weight Gain
Avoidance of food
Binge eating
Purging
Borsboom & Cramer, 2010; Borsboom & Cramer, 2013; Kendler, Zachar, & Craver, 2011

5. What can network analysis teach us?
Determine the symptoms that are central to the BN psychopathology network
Examine how symptoms of comorbid disorders interact with symptoms of BN

6. Focus interventions to target:
Clinical Utility
Reducing core symptoms in treatment should theoretically also decrease related symptoms
Focus interventions to target:
core symptoms−symptoms play a crucial role in the network
comorbid symptoms that link between multiple disorders
Hayes, Yasinski, Barnes, & Bockting, 2015

7. A network of BN symptoms:
Current study
Examined:
A network of BN symptoms:
Which symptoms are most central (i.e. core symptoms)?
The networks of BN, depression, and anxiety symptoms:
Which depression and anxiety symptoms are most strongly related to BN symptoms?

8. Participants
196 patients recruited for a clinical trial
All patients had DSM-IV diagnosis of BN
Primarily female (n = 187; 95.4%)
European American (n = 165; 84.2%)
Majority had comorbid depression and/or anxiety (n = 136; 69.4%)

9. Measures Eating Disorder Examination
Binge eating, restriction, fears of fatness
Short Evaluation of Eating Disorders
Vomiting, purging, excessive exercise
Beck Anxiety Inventory
Scared, dizziness
Beck Depression Inventory-II
Sad, fatigue, self-dislike
Bauer et al., 2005; Beck, Steer, & Brown, 1996; Fairburn & Cooper, 1993; Steer & Beck, 1997

10. Network analyses Partial Correlation Networks (Glasso Estimator)
Explains how symptoms relate while also considering the impact of all other symptoms
Bridge Symptoms
Symptoms that link adjacent symptoms together and are theorized to be pathways that could causally connect symptoms or behaviors
Centrality Measures
Betweenness – number of times symptom is passed through
Closeness – closeness to other symptoms in the network
Strength – having many connections to other symptoms

11. Bulimia Nervosa Psychopathology Network
BN Network

12. ** ** ** BETWEENESS CLOSENESS STRENGTH
**weight preoccupation
**weight dissatisfaction **
Higher peaks on right side indicate higher centrality
**highest centrality items
**lose weight **
**fear weight gain **

13. BN AND anxiety Network
Bulimia Nervosa &
Anxiety Network

14. BETWEENESS CLOSENESS STRENGTH
**weight preoccupation **
**unsteady
**terrified **
**shape dissatisfaction
Higher peaks on right side indicate higher centrality
**highest centrality items **
**lose control **
**fear weight gain
**choking ** **
**avoid eating

15. BN and depression network
Bulimia Nervosa &
Depression Network

16. BETWEENESS CLOSENESS STRENGTH
**weight preoccupation **
**sad **
Higher peaks on right side indicate higher centrality
**highest centrality items **
**irritable
**fear weight gain **
**concentrate **

17. Core BN symptoms CONCLUSIONS
fear of weight gain & overevaluation of weight and shape
Bridge symptoms - connect anxiety or depression symptoms to BN
Physical sensations: unsteady, fears of losing control, choking, difficulty concentrating may be bridge symptoms

18. Fear of weight gain is central to BN network
Binge eating and purging on the periphery
Treatments that focus on fear of weight gain may have maximal impact
Weekly weighing
Exposure

19. Physical sensations bridge BN & anxiety/depression
Exaggerated insula response in eating disorders?
Sensitivity to physical sensations
Interoceptive Exposures
Kim et al., 2012; Fassino, Pierò, Gramaglia, & Abbate-Daga, 2004; Klabunde et al., 2013; Oberndorfer et al., 2013

20. Data is cross-sectional – no causality
Limitations
Data is cross-sectional – no causality
Limited measurement of each symptom
Applying network analysis to psychopathology is new
No fit indices
No measures of reliability
Limited by measures and symptoms chosen for the network

21. Future directions
Does change in a core symptom produce changes in other network symptoms?
Do symptom networks become less strong after treatment and with symptom remission?

22. Acknowledgments & Disclosures
Dr. Bulik is a grant recipient and consultant for Shire Pharmaceuticals and has consulted for Ironshore. Dr. Marcus is on the Scientific Advisory Board of Weight Watchers International, Inc. Dr. Peat is recipient of a contract from RTI and Shire Pharmaceuticals and has consulted for Sunovion Pharmaceuticals, L.E.K consulting, and Nexus Global Solutions. Dr. Watson is supported by a research grant from Shire awarded to UNC-Chapel Hill. Dr. Zerwas has consulted for L.E.K consulting.
This research was supported by a National Institute of Mental Health (NIMH) grant (R01MH080065), a Clinical Translational Science Award (UL1TR000083), and the Alexander von Humboldt-Stiftung. Dr. Zerwas is supported by a NIMH career development grant (K01MH100435). Drs. Peat and Runfola were supported by a NIMH post-doctoral training grant (T32MH076694). Dr. Runfola was supported by the Global Foundation for Eating Disorders (PIs: Bulik and Baucom; Benjamin Zimmer was supported by a Fellowship for Postdoctoral Researchers from the German Academic Exchange Service (DAAD). Dr. Bulik acknowledges support from the Swedish Research Council (VR Dnr: ).
We wish to honor the incredible contribution and legacy of our colleague Dr. Robert Hamer, who passed away in December 2015.