title: Somatic and cognitive symptoms as indicators of potential endophenotypes in bipolar spectrum disorders: an exploratory and proof-of-concept study comparing bipolar II disorder with recurrent brief depression and healthy controls.
abstract: BACKGROUND
  We examined whether somatic symptoms reported by patients with bipolar spectrum disorder (BSD), in this study defined as bipolar II (BD-2) or recurrent brief depression with (RBD-H) or without (RBD-O) a history of hypomanic symptoms might point to the possible underlying disease markers (endophenotypes). We hypothesized that somatic symptoms that are possible indirect indicators of endophenotypes should be more prevalent among patients than among healthy controls; should not correlate with neuroticism; should not correlate with the severity of current mental status (e.g., anxiety, depression); and should not correlate with the use of psychotropic drugs including antiepileptics or be explained by co-morbid medical diseases.
  
  
  METHODS
  Sixty-one patients (BD-2: n=21; RBD-H: n=19; RBD-O: n=21) were compared with 21 healthy controls. Assessments included a 123-item somatic symptom checklist; assessments for neuroticism, anxiety and depression. Candidate somatic symptoms were selected using a 4-step inclusion/exclusion procedure.
  
  
  RESULTS
  Seven symptoms survived in all three groups: general (fatigue, feeling exhausted); sensory (leaden sensation in legs, pain in the body, impaired sense of smell); cognitive (loss of memory) and autonomic (excessive perspiration). In addition 15 symptoms survived in one or two groups (examples: impaired hearing, hypersensitivity to sound, inability to find words).
  
  
  CONCLUSIONS
  Possible selection bias and small sample size precludes firm conclusions with regards to specific symptoms.
  
  
  CONCLUSIONS
  Our approach identified symptoms for which an association with BSDs has been suggested previously, as well as symptoms not commonly associated with BSDs. The findings support the feasibility and validity of using assessment of somatic symptoms as an approach to identify potential endophenotypes in BSDs.
authors.affiliation: Department of Psychosomatic Medicine, Division of Surgery & Neuroscience, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Clinical Psychiatry, Sørlandet Hospital, Arendal, Norway. Electronic address: hans.lovdahl@sshf.no.
authors.forename: H
authors.initials: H
authors.lastname: Lövdahl
authors.affiliation: Department of Psychosomatic Medicine, Division of Surgery & Neuroscience, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Normood (Norwegian Research Network on Mood Disorders), Norway.
authors.forename: E
authors.initials: E
authors.lastname: Bøen
authors.affiliation: Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Adult Habilitation, Akershus University Hospital and Institute of Clinical Medicine, Campus Akershus University Hospital, University of Oslo, Norway.
authors.forename: E A
authors.initials: EA
authors.lastname: Malt
authors.affiliation: Department of Psychosomatic Medicine, Division of Surgery & Neuroscience, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Normood (Norwegian Research Network on Mood Disorders), Norway.
authors.forename: U F
authors.initials: UF
authors.lastname: Malt
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000150:complications / Q000503:physiopathology / Q000523:psychology*; D003072:Cognition Disorders / Q000150:complications*; D058068:Endophenotypes; D005260:Female; D006801:Humans; D008297:Male; D012008:Recurrence
keywords: Bipolar; Endophenotype; Giessener; RBD; Somatic; Symptom