title: Illness severity and biomarkers in depression: Using a unidimensional rating scale to examine BDNF.
abstract: BACKGROUND
  Numerous studies have reported reduced peripheral brain-derived neurotrophic factor (BDNF) in major depression (MD). However, most of these studies used multidimensional depression rating scales, and failed to identify a relationship between BDNF levels and depression severity. Unidimensional scales are a more valid measure of syndrome severity. In these scales, items are ordered in increasing severity, so that as scores increase, syndrome severity increases; thus, each item adds unique information, and items can be totaled to a meaningful sum. The current study used the HAM-D6, a unidimensional measure of depression, to examine if it could identify a correlation between serum BDNF and depression severity.
  
  
  METHODS
  Serum BDNF levels and symptom severity were assessed in 163 depressed patients, including those with both unipolar (84.0%) and bipolar (16.0%) depression. The evaluation of depression severity included the total HAM-D17 and 3 subscales, including the HAM-D6.
  
  
  RESULTS
  On average, patients presented moderate to severe depression (HAM-D17=21.2±5.5). Overall BDNF levels were 60.4±22.6ng/mL. The correlation between serum BDNF and depression severity was modest and not different when assessed by the HAM-D6 subscale or the HAM-D17 as a whole (z=0.951; p=0.341), despite being statistically significant for the HAM-D6 (r=-0.185; p=0.019; 95% CI: -0.335 to -0.033), but not for the entire HAM-D17 (r=-0.127; p=0.108; 95% CI: -0.272 to 0.027).
  
  
  CONCLUSIONS
  We could not identify a strong relationship between serum BDNF levels and depression severity using the HAM-D6. This is in concordance with results of previous studies that reported no correlation between these variables, and indicates that the properties of the clinical measures used cannot explain the results these studies.
authors.affiliation: Hospital de Clínicas de Porto Alegre, Department of Psychiatry, Porto Alegre, Brazil; Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil. Electronic address: mcaldieraro@hcpa.edu.br.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Caldieraro
authors.affiliation: Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil.
authors.forename: Edgar A
authors.initials: EA
authors.lastname: Vares
authors.affiliation: Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil.
authors.forename: Lívia H
authors.initials: LH
authors.lastname: Souza
authors.affiliation: Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil; Hospital São Lucas da Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Department of Psychiatry, Porto Alegre, Brazil.
authors.forename: Lucas
authors.initials: L
authors.lastname: Spanemberg
authors.affiliation: Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil.
authors.forename: Tadeu A
authors.initials: TA
authors.lastname: Guerra
authors.affiliation: Universidade Federal do Rio Grande do Sul (UFRGS), Programa de Pós-Graduação em Ciências Biológicas: Bioquimica, Porto Alegre, RS, Brazil.
authors.forename: Bianca
authors.initials: B
authors.lastname: Wollenhaupt-Aguiar
authors.affiliation: Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil.
authors.forename: Pâmela
authors.initials: P
authors.lastname: Ferrari
authors.affiliation: Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Nierenberg
authors.affiliation: Hospital de Clínicas de Porto Alegre, Department of Psychiatry, Porto Alegre, Brazil; Universidade Federal do Rio Grande do Sul (UFRGS), Department of Psychiatry and Forensic Medicine, Programa de Pós-Graduação Ciências Médicas: Psiquiatria, Porto Alegre, Brazil.
authors.forename: Marcelo P
authors.initials: MP
authors.lastname: Fleck
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001714:Bipolar Disorder / Q000097:blood* / Q000523:psychology; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood*; D003865:Major Depressive Disorder / Q000097:blood* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; D019208:Brain-Derived Neurotrophic Factor; C579455:BDNF protein, human