title: Can discrete event simulation be of use in modelling major depression?
abstract: BACKGROUND
  Depression is among the major contributors to worldwide disease burden and adequate modelling requires a framework designed to depict real world disease progression as well as its economic implications as closely as possible.
  
  
  OBJECTIVE
  In light of the specific characteristics associated with depression (multiple episodes at varying intervals, impact of disease history on course of illness, sociodemographic factors), our aim was to clarify to what extent "Discrete Event Simulation" (DES) models provide methodological benefits in depicting disease evolution.
  
  
  METHODS
  We conducted a comprehensive review of published Markov models in depression and identified potential limits to their methodology. A model based on DES principles was developed to investigate the benefits and drawbacks of this simulation method compared with Markov modelling techniques.
  
  
  RESULTS
  The major drawback to Markov models is that they may not be suitable to tracking patients' disease history properly, unless the analyst defines multiple health states, which may lead to intractable situations. They are also too rigid to take into consideration multiple patient-specific sociodemographic characteristics in a single model. To do so would also require defining multiple health states which would render the analysis entirely too complex. We show that DES resolve these weaknesses and that its flexibility allow patients with differing attributes to move from one event to another in sequential order while simultaneously taking into account important risk factors such as age, gender, disease history and patients attitude towards treatment, together with any disease-related events (adverse events, suicide attempt etc.).
  
  
  CONCLUSIONS
  DES modelling appears to be an accurate, flexible and comprehensive means of depicting disease progression compared with conventional simulation methodologies. Its use in analysing recurrent and chronic diseases appears particularly useful compared with Markov processes.
authors.affiliation: Laboratoire d'Analyse des Systèmes de Santé, Université Claude Bernard, Lyon 1, France. agathelelay@gmail.com
authors.forename: Agathe
authors.initials: A
authors.lastname: Le Lay
authors.forename: Nicolas
authors.initials: N
authors.lastname: Despiegel
authors.forename: Clément
authors.initials: C
authors.lastname: François
authors.forename: Gérard
authors.initials: G
authors.lastname: Duru