title: Modeling and treating internalizing psychopathology in a clinical trial: a latent variable structural equation modeling approach.
abstract: BACKGROUND
  Clinical trials are typically designed to test the effect of a specific treatment on a single diagnostic entity. However, because common internalizing disorders are highly correlated ('co-morbid'), we sought to establish a practical and parsimonious method to characterize and quantify changes in a broad spectrum of internalizing psychopathology targeted for treatment in a clinical trial contrasting two transdiagnostic psychosocial interventions.
  
  
  METHODS
  Alcohol dependence treatment patients who had any of several common internalizing disorders were randomized to a six-session cognitive-behavioral therapy (CBT) experimental treatment condition or a progressive muscle relaxation training (PMRT) comparison treatment condition. Internalizing psychopathology was characterized at baseline and 4 months following treatment in terms of the latent structure of six distinct internalizing symptom domain surveys.
  
  
  RESULTS
  Exploratory structural equation modeling (ESEM) identified a two-factor solution at both baseline and the 4-month follow-up: Distress (measures of depression, trait anxiety and worry) and Fear (measures of panic anxiety, social anxiety and agoraphobia). Although confirmatory factor analysis (CFA) demonstrated measurement invariance between the time-points, structural models showed that the latent means of Fear and Distress decreased substantially from baseline to follow-up for both groups, with a small but statistically significant advantage for the CBT group in terms of Distress (but not Fear) reduction.
  
  
  CONCLUSIONS
  The approach demonstrated in this study provides a practical solution to modeling co-morbidity in a clinical trial and is consistent with converging evidence pointing to the dimensional structure of internalizing psychopathology.
authors.affiliation: Department of Psychiatry, University of Minnesota, Minneapolis, MN, USA. kushn001@umn.edu
authors.forename: M G
authors.initials: MG
authors.lastname: Kushner
authors.forename: R F
authors.initials: RF
authors.lastname: Krueger
authors.forename: M M
authors.initials: MM
authors.lastname: Wall
authors.forename: E W
authors.initials: EW
authors.lastname: Maurer
authors.forename: J S
authors.initials: JS
authors.lastname: Menk
authors.forename: K R
authors.initials: KR
authors.lastname: Menary
mesh_terms: D000328:Adult; D000437:Alcoholism / Q000453:epidemiology / Q000628:therapy; D001008:Anxiety Disorders / Q000453:epidemiology / Q000628:therapy*; D015928:Cognitive Behavioral Therapy / Q000379:methods*; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology / Q000628:therapy*; D005081:Exercise Therapy / Q000379:methods*; D005239:Fear / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D009126:Muscle Relaxation / Q000502:physiology; D013315:Stress, Psychological / Q000453:epidemiology / Q000628:therapy; D016896:Treatment Outcome