What does the term "depression" mean in Parkinson's disease?

The overlap of the features of Parkinson's disease (PD) and affective disorder is likely to produce an increased rate of diagnosis for depressive disorders in PD patients. Although the literature alludes to these problems, no systematic investigation of the extent of this has yet been undertaken. A cross-sectional comparison of the Present State Examination (PSE) profiles and diagnoses between 52 PD subjects, 32 healthy control subjects and 30 depressed subjects was performed. The PSE profile of the PD group was very similar to that found by Brown and MacCarthy (1990), and consisted mostly of non-specific symptoms. The prevalence rate for depressive disorders in PD was 3.4%. The PSE profile of the PD subjects was similar to the profile of the control group rather than the depressed group. When the diagnostic cut-off values on the Beck depression inventory (BDI), Hamilton depression rating scale (HDRS), Montgomery Asberg depression rating scale (MADRS) and the Hospital anxiety and depression scale (HAD) were compared with the PSE diagnoses, the accepted cut-off values for the BDI, MADRS and HAD were found to be overinclusive producing a spuriously high prevalence rate. The accepted cut-off value for the HDRS may be acceptable. The excess was due to items on the rating scales contaminated by the features of Parkinson's disease. The DSM-III diagnostic criteria were also overinclusive. The validated cut-off for the MADRS was applied to longitudinal data. Survival analysis revealed the incidence of depressive disorders in PD to be 43 per 1000 person-years.