title: Square wave jerks and anxiety as distinctive biomarkers for anorexia nervosa.
abstract: OBJECTIVE
  The factors contributing to the cause and maintenance of anorexia nervosa (AN) are poorly understood, though increasing interest surrounds the neurobiological underpinnings of the condition. The examination of saccadic eye movements has proven useful in our understanding of the neurobiology of some other psychiatric illnesses, as they utilize identifiable brain circuits. Square wave jerks (SWJs), which describe an involuntary saccade away and back to fixation, have been observed to occur at abnormally high rates in neurodegenerative disorders and some psychiatric illnesses, but have not been examined in AN. Therefore, the aim of this study was to investigate whether individuals with AN and healthy control (HC) individuals differ in SWJ rate during attempted fixation.
  
  
  METHODS
  Square wave jerk frequency was compared across 23 female participants with AN and 22 HC participants matched for age, sex, and premorbid intelligence.
  
  
  RESULTS
  Anorexia nervosa participants were found to make SWJs at a significantly higher rate than HC participants. The rate of SWJs in AN was also found to negatively correlate with anxiety. Square wave jerk rate and anxiety were found to correctly classify groups, with an accuracy of 87% for AN participants and 95.5% for HCs.
  
  
  CONCLUSIONS
  Given our current understanding of saccadic eye movements, the findings suggest a potential role of γ-aminobutyric acid (GABA) in the superior colliculus, frontal eye fields, or posterior parietal cortex in the psychopathology of AN.
authors.affiliation: Department of Optometry & Vision Sciences, The University of Melbourne, Melbourne, Australia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Phillipou
authors.affiliation: Brain and Psychological Sciences Research Centre, Swinburne University of Technology, Hawthorn, Melbourne, Australia.
authors.forename: Susan Lee
authors.initials: SL
authors.lastname: Rossell
authors.affiliation: Department of Psychiatry, The University of Melbourne, Melbourne, Australia Department of Psychiatry, St Vincent's Hospital, Fitzroy, Melbourne, Australia Faculty of Health Sciences, Australian Catholic University, Fitzroy, Melbourne, Australia.
authors.forename: David Jonathan
authors.initials: DJ
authors.lastname: Castle
authors.affiliation: Monash Alfred Psychiatry Research Centre, Melbourne, Australia.
authors.forename: Caroline
authors.initials: C
authors.lastname: Gurvich
authors.affiliation: Department of Optometry & Vision Sciences, The University of Melbourne, Melbourne, Australia.
authors.forename: Larry Allen
authors.initials: LA
authors.lastname: Abel
mesh_terms: D000856:Anorexia Nervosa / Q000175:diagnosis* / Q000503:physiopathology; D001007:Anxiety / Q000175:diagnosis* / Q000503:physiopathology; D003937:Diagnosis, Differential; D005260:Female; D005403:Fixation, Ocular; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D012438:Saccades / Q000502:physiology*; D055815:Young Adult
keywords: anorexia nervosa; biomarker; neurobiology; saccadic intrusions; square wave jerks