title: Is depression in Parkinson's disease (PD) a specific entity?
abstract: BACKGROUND
  Clinical lore and research have suggested for a long time that depression and PD are closely related. We examined the validity of depression associated with PD (dPD) as a specific subtype of depression according to face validity, descriptive validity, construct validity and predictive validity.
  
  
  METHODS
  The English literature was reviewed after searching the MEDLINE database up to June 2010.
  
  
  RESULTS
  There appears to be three possible subtypes of comorbid depression: 1) patients who would have been depressed even if they had no PD (nonspecific-casual comorbid dPD), 2) patients who would have been depressed if they had had another disabling medical illness (nonspecific-reactive comorbid dPD) 3) those for which depression is directly related to the underlying pathophysiology of PD (specific comorbid dPD). These latter patients may more often present with particular clinical characteristics (descriptive validity): absence of history of depression or only within 5 years prior to onset of PD, absence of guilty thoughts and self-blame, absence of suicidal behavior, right-sided onset. However, dPD is only partly responsive to dopamine replacement and cannot be solely explained by dopamine deficiency. Other neurotransmitter systems are affected in PD and are involved in the pathophysiology of dPD. Their relative involvement however may differ from that in idiopathic depression (i.e.: lesser involvement of serotonergic systems).
  
  
  CONCLUSIONS
  Therapeutic data are limited to few controlled trials.
  
  
  CONCLUSIONS
  Further research may allow differential diagnosis between dPD subtypes (i.e.: those who do and do not result from the underlying pathophysiological process of PD) and help inform treatment choice.
authors.affiliation: Clinique des Maladies Mentales et de l'Encéphale, Centre Hospitalier Sainte-Anne, Paris, France. c.even@ch-sainte-anne.fr
authors.forename: Christian
authors.initials: C
authors.lastname: Even
authors.forename: Daniel
authors.initials: D
authors.lastname: Weintraub
mesh_terms: D015897:Comorbidity; D003863:Depression / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics / Q000503:physiopathology; D004298:Dopamine / Q000502:physiology; D006801:Humans; D008297:Male; D018377:Neurotransmitter Agents / Q000502:physiology; D010300:Parkinson Disease / Q000150:complications / Q000453:epidemiology* / Q000235:genetics / Q000503:physiopathology; D014481:United States
chemical_list: D018377:Neurotransmitter Agents; D004298:Dopamine