OBJECTIVE: The objectives are twofold: 1- To review the impact of depression on cognition of patients with Parkinson's disease (DP) 2- To assess whether depression is a risk factor for PD and cognitive deficit in PD. METHODOLOGY: The bibliographical review considered the 1967-2003 period (Medline), using the keywords Parkinson's disease, depression and cognition. Only clinical cross-sectional, prospective and case control studies were included. RESULTS: Five articles showed a positive conclusion as to the impact of depression on cognition in PD, whereas four showed the opposite. Depression is a risk factor for PD as PD is a risk factor for depression. On the other hand, it was impossible to draw a conclusion about depression as a risk factor for cognitive disorders in patients with PD. Depression in patients with PD is associated with advancing disease severity, high Hoehn and Yahr, high Unified Parkinson's Disease Rating Scale (UPDRS), falls, low Mini-Mental State Examination (MMSE) and Schwab and England scores, impaired cognitive functions, axial bradykinesia, gait and balance impairment, advanced age, female gender and thought disorders. CONCLUSION: The interaction between depression and PD is complex and bi-directional. Therefore, depression is a risk factor for PD as PD is a risk factor for depression. There is a homogeneous profile of depression patients with DP at risk to develop cognitive disorders. On the other hand, it is not possible to establish depression as a risk factor for cognitive disorders in PD. Further studies with representative samples and defined diagnosis criteria are needed to provide more information on this subject.
Parkinson's disease; depression; cognition
