title: Conceptual model and cluster analysis of behavioral symptoms in two cohorts of adults with traumatic brain injuries.
abstract: BACKGROUND
  Behavioral changes often occur after moderate-to-severe traumatic brain injury (TBI) and can lead to poor health, psychosocial functioning, and quality of life. Challenges in evaluating these behaviors often result from the complexity and variability in the way they are conceptualized and defined. We propose and test a conceptual model that is specific to behavioral symptoms after TBI, to serve as a basis for better assessment and treatment. We hypothesized that clusters of individuals, with unique emotional, cognitive, and behavioral characteristics, would emerge that would illustrate this conceptual model.
  
  
  METHODS
  We conducted model-based cluster analyses in two cohorts, 6-months post-injury (n = 79) and >6 months post-injury (n = 62), of adults with moderate-to-severe TBI to explore the face validity of our conceptual model by evaluating how participants clustered with regard to emotional (Patient Health Questionnaire 9, Positive and Negative Affect Schedule), cognitive (neuropsychological test battery), and frontal behavioral (Frontal Systems Behavior Scale) symptoms.
  
  
  RESULTS
  In each cohort, unique clusters of participants emerged that differed significantly with regard to emotional state, cognition, and behavior (ps<.05). Those 6-months post-injury clustered along a general continuum of symptom severity in emotional and behavioral symptom domains, from no impairment to severe impairment. Clusters in the chronic cohort (>6 months) demonstrated a more complex pattern of symptoms; the most severe behavioral symptoms occurred in the context of severe emotional symptoms, even in the absence of cognitive impairment. However, problematic behavioral symptoms were also present in the context of severe cognitive impairment, even in the absence of emotional symptoms.
  
  
  CONCLUSIONS
  Emotional, cognitive, and behavioral characteristics were represented as expected, based on the proposed conceptual model of behavior. This conceptual model provides the basis for evaluating behavioral changes after moderate-to-severe TBI and identifying modifiable targets and relevant subpopulations for behavioral intervention, with the goal of improved evidence-based personalized medicine for this population.
authors.affiliation: a Department of Physical Medicine and Rehabilitation , University of Pittsburgh School of Medicine , Pittsburgh , PA , USA.
authors.forename: Shannon B
authors.initials: SB
authors.lastname: Juengst
authors.affiliation: b Department of Medicine , University of Pittsburgh , Pittsburgh , PA , USA.|c Department of Psychiatry , University of Pittsburgh School of Medicine , Pittsburgh , PA , USA.
authors.forename: Galen
authors.initials: G
authors.lastname: Switzer
authors.affiliation: d Department of Rehabilitation , Seoul National University Hospital , Seoul , South Korea.
authors.forename: Byung Mo
authors.initials: BM
authors.lastname: Oh
authors.affiliation: a Department of Physical Medicine and Rehabilitation , University of Pittsburgh School of Medicine , Pittsburgh , PA , USA.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Arenth
authors.affiliation: a Department of Physical Medicine and Rehabilitation , University of Pittsburgh School of Medicine , Pittsburgh , PA , USA.|e Center for Neuroscience , University of Pittsburgh , Pittsburgh , PA , USA.|f Safar Center for Resuscitation Research , University of Pittsburgh , Pittsburgh , PA , USA.
authors.forename: Amy K
authors.initials: AK
authors.lastname: Wagner
mesh_terms: D000328:Adult; D000342:Affective Symptoms / Q000209:etiology / Q000523:psychology; D001526:Behavioral Symptoms / Q000503:physiopathology / Q000523:psychology*; D000070642:Brain Injuries, Traumatic / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000523:psychology*; D016000:Cluster Analysis; D003072:Cognition Disorders / Q000209:etiology / Q000523:psychology; D015331:Cohort Studies; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009483:Neuropsychological Tests; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
keywords: Behavioral symptoms; Brain injuries; Cluster analysis; Cognition.; Emotions