1. Psychopathology Network Analysis Workshop
Eiko Fried
Marie Deserno
Sacha Epskamp
Department of Psychological Research Methods
University of Amsterdam
Harvard University, June 2nd – 3rd 2016

2. Marie Deserno Eiko Fried Sacha Epskamp
Eiko Fried
Sacha Epskamp
Department of Psychological Research Methods
University of Amsterdam

3. Introduction to Psychopathological Networks Network Estimation
Outline day 1
Introduction to Psychopathological Networks
Network Estimation
Network Inference
Network Stability
Practical with Borderline Data
Advanced Techniques
FAQ

4. Complexity trumps reductionism
Introduction
Complexity trumps reductionism
Why symptoms cluster in syndromes: common cause vs. network models

5. Complexity trumps reductionism
Chapter 1
Complexity trumps reductionism

13. What are networks (preview)
A network is a set of nodes connected by a set of edges
Nodes are also called vertices
Edges are also called links
Networks are also called graphs

14. Why symptoms cluster in syndromes
Chapter 2
Why symptoms cluster in syndromes

15. Natural kinds
Robert Koch, 1905: discovery that specific diseases have specific causative agents (tuberculosis & syphilis)
Diseases understood as natural kinds:
Unchanging and ahistoric entities with sharp boundaries that have a specific set of properties (e.g., symptoms) both necessary and sufficient for classification
Measles: infection of the respiratory system caused by a specific virus, accompanied by specific symptoms like red eyes, fever, generalized rash, and Koplik's spots
Gold: atomic number 79, and everything with this atomic number is gold
At the turn of the 19th century, Koch discovered …

16. Natural kinds
1910: discovery of syphilitic bacteria in brains of deceased patients diagnosed with "general paralysis of the insane"
Neuropsychiatric syndrome of late-stage syphilis
Clear "essence" identified for a mental disorder
Disease model applied to the rest of medicine, including psychiatry
1912, Alfred Roche:
"The main example of a happy final definition of a disease condition […] has been general paresis. The success achieved here has perhaps been a misfortune in its side effects because it nourished the illusion that something similar might soon be repeated."
At the turn of the 19th century, Koch discovered …

17. Natural kinds 1959, Kurt Schneider:
"General paresis […] became the model for forming disease entities. It was thought it would continue thus, it was hoped that with time more and more such disease entities would emerge from the multifarious conditions of the mentally ill. In fact, however, this did not happen."
At the turn of the 19th century, Koch discovered …

18. Mental disorders as natural kinds
The assumption of mental disorders as natural kinds has been present throughout the history of psychiatry
Gerald Klerman, chief of the US national mental health agency, 1978:
"there is a boundary between the normal and the sick"
"there are discrete mental disorders"
Aim of developing specific treatments for particular disorders, and of finding specific underlying biological abnormalities
At the turn of the 19th century, Koch discovered …

19. Mental disorders as natural kinds
This is more than just a belief—reflected in everyday research practices
Disparate symptoms added to sum-scores, thresholds distinguish between case and controls
Search for potential causes then proceeds as if disorders are natural kinds, similar to measles
This perspective has discouraged attention to specific depression symptoms and their dynamic interactions

20. Common cause framework
Related to notion of natural kinds
Disorders itself are latent—we cannot observe measles directly M

21. Common cause framework
Related to notion of natural kinds
Disorders itself are latent—we cannot observe measles directly
We can only observe the symptoms of measles
We can use symptoms to indicate the presence of measles s1 M s2 s3

22. Common cause framework
Related to notion of natural kinds
Disorders itself are latent—we cannot observe measles directly
We can only observe the symptoms of measles
We can use symptoms to indicate the presence of measles
This works because measles causes measles symptoms s1 M s2 s3

23. Common cause framework
The CC framework is responsible for symptom checklists in the rest of medicine and psychiatry
We use symptom lists to determine the presence of an underlying disease
The CC framework explains why symptoms cluster: they have the same causal origin
Fever, generalized rash, Koplik's spots  measles! s1 s2 s3 M

24. Common cause framework
What does this mean for symptoms?
Symptoms are equivalent & interchangeable indicators of underlying disease ("assumption of symptom equivalence")
Symptom number, not symptom nature is relevant
Symptoms are "locally independent"; since they are derived from the same common cause, their correlations are spurious 72 74 73 W

25. Common cause framework
What does this mean for symptoms?
Symptoms are equivalent & interchangeable indicators of underlying disease ("assumption of symptom equivalence")
Symptom number, not symptom nature is relevant
Symptoms are "locally independent"; since they are derived from the same common cause, their correlations are spurious 72 74 73 W

26. Network perspective
Traditional: symptoms cluster because of a shared origin
Network view: symptoms cluster because they influence each other.

27. Network perspective
Symptoms have autonomous causal power and are not mere passive consequences of a common cause

28. Network perspective
Symptoms are separate entities that can differ in important aspects
Symptoms are not interchangeable indicators of an underlying disorder.

29. Standard argument
Analyzing sums of depression symptoms is problematic because:
Depression is highly heterogeneous ( /j.jad )
Depression scales are not unidimensional ( /pas )
Individual symptoms are differentially related to important variables like impaired functioning, risk factors, or biomarkers ( /s ; /fpsyg ; /S ; /journal.pone )
We need to focus on the analysis of individual symptoms and their causal dynamics instead of sum-scores ( /fpsyt )

30. Disclaimer
There is nothing wrong with the idea that common causes trigger symptoms
Trauma → PTSD symptoms
Traumatic brain injury → affective symptoms
Particular life events → particular depression symptoms
There is nothing wrong with structural equation models / factor models, and not all models imply a common cause (e.g., formative models)
BUT: it may be interesting to explore to what degree problems of mental health may be better described as a causal system instead of an underlying common cause.

31. Network perspective
Network research may help us gain important insights in a number of research domains
Comorbidity
Centrality & clinical relevance of symptoms
Nomothetic & idiographic processes
Missing heritability
Network research may help us gain important insights into a number of disorders

32. Comorbidity
DOI /S X

33. Comorbidity
DOI /abn

34. Comorbidity
DOI /journal.pone

35. Centrality
A central symptom is one that exhibits a large number of connections in a network; switching on this symptom will likely spread symptom activation throughout the network
A peripheral symptoms is on the corner of a network and has few connections
Clinicians …
judge causally central symptoms to be more typical symptoms
recall central symptoms with greater accuracy than peripheral symptoms
use central symptoms more for diagnosing patients
DOI //

36. DOI /j.jad

37. Nomothetic vs idiographic information
DOI /S ; Master Thesis by Renske Kroeze, 2014

38. Missing heritability
Genetic liability in edges instead of nodes?

39. Network perspective
Useful to gain insights into a number of disorders

40. Substance abuse networks
DOI /j.drugalcdep

41. Substance abuse networks
DOI /j.drugalcdep

42. Substance abuse networks
DOI /j.drugalcdep

43. PTSD
DOI /

44. Bereavement
DOI /abn