title: Disturbances in Hypothalamic-Pituitary-Adrenal Axis and Immunological Activity Differentiating between Unipolar and Bipolar Depressive Episodes.
abstract: BACKGROUND
  Differentiating bipolar depression (BD) from unipolar depression (UD) is difficult in clinical practice and, consequently, accurate recognition of BD can take as long as nine years. Research has therefore focused on the discriminatory capacities of biomarkers, such as markers of the hypothalamic-pituitary-adrenal (HPA) axis or immunological activity. However, no previous study included assessments of both systems, which is problematic as they may influence each other. Therefore, this study aimed to explore whether cortisol indicators and inflammatory markers were a) independently associated with and/or b) showed effect modification in relation to a lifetime (hypo)manic episode in a large sample of depressed patients.
  
  
  METHODS
  Data were derived from the Netherlands Study of Depression and Anxiety and comprised 764 patients with a DSM-IV depressive disorder at baseline, of which 124 (16.2%) had a lifetime (hypo)manic episode at the 2-year assessment, or a more recent episode at the 4-year or 6-year assessment. Baseline cortisol awakening response, evening cortisol and diurnal cortisol slope were considered as cortisol indicators, while baseline C-reactive Protein (CRP), Interleukin-6 (IL-6), and Tumor Necrosis Factor Alpha (TNF-α) were included as inflammatory markers.
  
  
  RESULTS
  In depressed men and women, none of the cortisol indicators and inflammatory markers were (independently) associated with a (hypo)manic episode. However, effect modification was found of diurnal cortisol slope and CRP in relation to a (hypo)manic episode. Further analyses showed that depressed men with high levels of diurnal cortisol slope and CRP had an increased odds (OR=10.99, p=.001) of having a (hypo)manic episode. No significant differences were found in women.
  
  
  CONCLUSIONS
  Our findings suggest that the combination of high diurnal cortisol slope and high CRP may differentiate between UD and BD. This stresses the importance of considering HPA-axis and immunological activity simultaneously, but more research is needed to unravel their interrelatedness.
authors.affiliation: University of Groningen, University Medical Center Groningen, Interdisciplinary Center Psychopathology and Emotion regulation (ICPE) and University Center Psychiatry (UCP), Groningen, The Netherlands.
authors.forename: Karlijn
authors.initials: K
authors.lastname: Becking
authors.affiliation: PsyQ Rijnmond, Department of Mood Disorders, Rotterdam, The Netherlands.
authors.forename: Annet T
authors.initials: AT
authors.lastname: Spijker
authors.affiliation: PsyQ Rijnmond, Department of Mood Disorders, Rotterdam, The Netherlands; Leiden University, Institute of Psychology, Leiden, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Hoencamp
authors.affiliation: University of Groningen, University Medical Center Groningen, Interdisciplinary Center Psychopathology and Emotion regulation (ICPE) and University Center Psychiatry (UCP), Groningen, The Netherlands; VU University Medical Center, Department of Psychiatry and EMGO+ Institute for Health and Care Research, Amsterdam, The Netherlands; Leiden University Medical Center, Department of Psychiatry, Leiden, The Netherlands.
authors.forename: Brenda W J H
authors.initials: BW
authors.lastname: Penninx
authors.affiliation: University of Groningen, University Medical Center Groningen, Interdisciplinary Center Psychopathology and Emotion regulation (ICPE) and University Center Psychiatry (UCP), Groningen, The Netherlands.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Schoevers
authors.affiliation: University of Groningen, University Medical Center Groningen, Interdisciplinary Center Psychopathology and Emotion regulation (ICPE) and University Center Psychiatry (UCP), Groningen, The Netherlands.
authors.forename: Lynn
authors.initials: L
authors.lastname: Boschloo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001714:Bipolar Disorder / Q000097:blood*; D002097:C-Reactive Protein / Q000378:metabolism; D003863:Depression / Q000097:blood*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D010913:Pituitary-Adrenal System / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D002097:C-Reactive Protein; D006854:Hydrocortisone