title: Random-mood interpretation of determinants for major depression.
abstract: BACKGROUND
  It has recently been proposed that major depression disorder (MDD) may, in a heterogeneous population-based cohort, be interpreted in terms of a random-mood model. Mood fluctuations are thought to result from stressors that occur randomly in time. We have investigated whether this concept also holds for more homogeneous groups, defined by known determinants for MDD, and whether the model's parameters, susceptibility (Z) and relaxation time (T), may be evaluated and used to differentiate between subcohorts.
  
  
  METHODS
  From a large epidemiological survey, the Netherlands Mental Health Survey and Incidence Study (NEMESIS), data on the duration of MDD were obtained for subcohorts, based on gender, severity of depression, recurrence and co-morbidity with dysthymia, anxiety and somatic disorder, and were compared with random-mood simulation calculations.
  
  
  RESULTS
  Susceptibility, Z, is empirically found to be proportional to incidence and may be identified with a risk ratio. A second scaling rule states the proportionality of mean duration with the product of Z and T. This Z-T classification proves to be more sensitive than conventional significance tests. Notably for men/women and for co-morbid anxiety, differences are seen that have previously gone unnoticed.
  
  
  CONCLUSIONS
  Depression may be conceptualized as a disorder resulting from random-mood fluctuations, the response to which is influenced by a large variety of determinants or risk factors. The model's parameters can be evaluated and may be used in differentiating between risk factor-defined subgroups.
authors.affiliation: Department of Psychiatry, University Medical Centre Groningen, University of Groningen, The Netherlands.
authors.forename: Kirsten I
authors.initials: KI
authors.lastname: Kaptein
authors.forename: Peter
authors.initials: P
authors.lastname: De Jonge
authors.forename: Jakob
authors.initials: J
authors.lastname: Korf
authors.forename: Jan
authors.initials: J
authors.lastname: Spijker
authors.forename: Ron
authors.initials: R
authors.lastname: De Graaf
authors.forename: Siebren Y
authors.initials: SY
authors.lastname: Van Der Werf
mesh_terms: D000223:Adaptation, Psychological; D000293:Adolescent; D000328:Adult; D000339:Affect; D001008:Anxiety Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D015331:Cohort Studies; D015897:Comorbidity; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology*; D019263:Dysthymic Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D009426:Netherlands; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D013001:Somatoform Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D013315:Stress, Psychological / Q000150:complications*