Modeling Avoidance in Mood and Anxiety Disorders Using Reinforcement Learning.
BACKGROUND
Serious and debilitating symptoms of anxiety are the most common mental health problem worldwide, accounting for around 5% of all adult years lived with disability in the developed world. Avoidance behavior-avoiding social situations for fear of embarrassment, for instance-is a core feature of such anxiety. However, as for many other psychiatric symptoms the biological mechanisms underlying avoidance remain unclear.


METHODS
Reinforcement learning models provide formal and testable characterizations of the mechanisms of decision making; here, we examine avoidance in these terms. A total of 101 healthy participants and individuals with mood and anxiety disorders completed an approach-avoidance go/no-go task under stress induced by threat of unpredictable shock.


RESULTS
We show an increased reliance in the mood and anxiety group on a parameter of our reinforcement learning model that characterizes a prepotent (pavlovian) bias to withhold responding in the face of negative outcomes. This was particularly the case when the mood and anxiety group was under stress.


CONCLUSIONS
This formal description of avoidance within the reinforcement learning framework provides a new means of linking clinical symptoms with biophysically plausible models of neural circuitry and, as such, takes us closer to a mechanistic understanding of mood and anxiety disorders.
Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
Anahit
A
Mkrtchian
Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
Jessica
J
Aylward
Gatsby Computational Neuroscience Unit, University College London, London, United Kingdom.
Peter
P
Dayan
Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
Jonathan P
JP
Roiser
Institute of Cognitive Neuroscience, University College London, London, United Kingdom. Electronic address: oliver.j.robinson@gmail.com.
Oliver J
OJ
Robinson
D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000523:psychology*; D001362:Avoidance Learning / Q000502:physiology*; D001499:Bayes Theorem; D003657:Decision Making / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D019964:Mood Disorders / Q000523:psychology* / Q000534:rehabilitation; D011569:Psychiatric Status Rating Scales; D012054:Reinforcement, Psychology; D055815:Young Adult
Anxiety; Avoidance; Diathesis–stress; Pavlovian bias; Reinforcement learning; Threat of shock