Depressive symptoms commonly occur in Parkinson's disease (PD), affecting approximately 40% of patients in cross-sectional studies.1–3 Depressive symptoms have also been recognized to be a major determinant of health-related quality of life in PD, and can affect functional ability, cognitive function, and caregiver quality of life.4–6 It is, therefore, important to recognize and assess depressive symptoms in patients with PD adequately. The gold standard for the diagnosis of depressive disorder at present are the criteria of the Diagnostic and Statistical Manual, Fourth Edition (DSM-IV), of the American Psychiatric Association. However, in clinical practice and research studies, particularly in epidemiological studies, surveys, and treatment trials measuring severity of depressive symptoms, use of DSM-IV criteria often is not feasible or useful. Several rating scales for screening and/or assessment of severity of depression are available and have been used widely to assess depression in patients with and without PD. However, there are several methodological difficulties in assessing depressive symptoms in PD, and it is unclear which scales are suitable for the assessment of depression in this patient group. The Movement Disorder Society (MDS) Task Force on Rating Scales for Parkinson's Disease therefore commissioned a critique of existing scales as applied to Parkinson's disease and to place them in a clinical and clinimetric context, similar to MDS reviews of the Unified Parkinson's Disease Rating Scale (UPDRS)7 and Hoehn & Yahr staging system.8 The purpose of this effort was the evaluation of all commonly used or appropriate rating scales for depression in PD (dPD) and to make recommendations on the utilization of specific scales and their need for modifications or replacement in this population.
The DSM-IV criteria for depressive disorder are the current gold standard against which such scales are compared. However, the use of these criteria (or other criteria such as the those of the International Classification of Diseases [ICD-10]) in PD has shortfalls, and recommendations have been made to revise the DSM-IV criteria for depressive disorder when applied to PD to overcome these methodological difficulties.9 Although a discussion of the validity of these criteria for depression in patients with PD is not the subject of this manuscript, these problems and their impact on the use of scales to assess of presence and severity of depression in patients with PD are recognized and discussed.