Validity of the Cornell scale for depression in dementia in Parkinson's disease with and without cognitive impairment

Depressive disturbances affect up to 50% of patients with Parkinson’s disease (PD) and negatively impact quality of life.1,2 Several studies have shown that depressive symptom rating scales are valid measures of depression in PD populations; however, depression rating scales have not been evaluated in patients with PD-dementia.3 Given that dementia develops in up to 80% of patients with PD, valid tools are needed to assess depression, irrespective of the patient’s cognitive status, over the course of the disease.4,5 The Cornell Scale for Depression in Dementia (CSDD), a rater-administered instrument, has potential for this purpose; it was developed specifically for assessment of depression in dementia and has been validated in both demented and non-demented geriatric patients.6,7 An important feature of the CSDD is that ratings are based on information obtained from clinical observation and interviews with the patient and an informant. As validation studies in PD have not been conducted, this study investigated the discriminant validity of the CSDD in a PD sample relative to a clinical assessment for depression.