title: A new chronobiological approach to discriminate between acute and chronic depression using peripheral temperature, rest-activity, and light exposure parameters.
abstract: BACKGROUND
  Circadian theories for major depressive disorder have suggested that the rhythm of the circadian pacemaker is misaligned. Stable phase relationships between internal rhythms, such as temperature and rest/activity, and the external day-night cycle, are considered to be crucial for adapting to life in the external environmental. Therefore, the relationship and possible alterations among (i) light exposure, (ii) activity rhythm, and (iii) temperature rhythm could be important factors in clinical depression. This study aimed to investigate the rhythmic alterations in depression and evaluate the ability of chronobiological parameters to discriminate between healthy subjects and depressed patients.
  
  
  METHODS
  Thirty female subjects, including healthy subjects, depressed patients in the first episode, and major recurrent depression patients. Symptoms were assessed using Hamilton Depression Scale, Beck Depression Inventory and Montgomery-Äsberg Scale. Motor activity, temperature, and light values were determined for 7 days by actigraph, and circadian rhythms were calculated.
  
  
  RESULTS
  Depressed groups showed a lower amplitude in the circadian rhythm of activity and light exposure, but a higher amplitude in the rhythm of peripheral temperature. The correlation between temperature and activity values was different in the day and night among the control and depressed groups. For the same level of activity, depressed patients had lowest temperature values during the day. The amplitudes of temperature and activity were the highest discriminant parameters.
  
  
  CONCLUSIONS
  These results indicate that the study of rhythms is useful for diagnosis and therapy for depressive mood disorders.
authors.affiliation: Laboratório de Cronobiologia do Hospital de Clínicas de Porto Alegre (HCPA), da Universidade Federal do Rio Grande do Sul (UFRGS), Ramiro Barcelos, 2350 sala 12107, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: Cláudia
authors.initials: C
authors.lastname: Ávila Moraes
authors.forename: Trinitat
authors.initials: T
authors.lastname: Cambras
authors.forename: Antoni
authors.initials: A
authors.lastname: Diez-Noguera
authors.forename: Regina
authors.initials: R
authors.lastname: Schimitt
authors.forename: Giovana
authors.initials: G
authors.lastname: Dantas
authors.forename: Rosa
authors.initials: R
authors.lastname: Levandovski
authors.forename: Maria Paz
authors.initials: MP
authors.lastname: Hidalgo
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D002908:Chronic Disease; D002940:Circadian Rhythm / Q000502:physiology; D003866:Depressive Disorder / Q000175:diagnosis / Q000503:physiopathology; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008027:Light; D009043:Motor Activity / Q000502:physiology*; D011569:Psychiatric Status Rating Scales