Background: In patients with Parkinson's disease (PD), depressive symptom rating scales facilitate identification of depressive disorders, which are common and disabling. Anxiety disturbances in PD, which lack valid assessment scales, frequently co-occur with PD-depression, are under-recognized, and require different interventions than depressive disorders. Whether high anxiety rates in PD confound depression scale performance or if any depression scales also predict anxiety disturbances is not known.
Objective: To test the impact of co-occurring anxiety disorders on psychometric properties of depression rating scales in depressed PD patients and compare disability between PD patients with anxiety, depression, and comorbid anxiety and depressive disorders.
Methods: PD subjects (n = 229) completed self-report and clinician-administered depression scales. Receiver operating characteristic curves were developed to estimate psychometric properties of each scale in those with depression alone, anxiety alone, and comorbid depression and anxiety. Between-group differences on all measures were examined.
Results: Comorbid anxiety did not affect the psychometric properties of any scale when identifying depressive disorders, but is associated with greater symptom severity and disability. Depression-scale scores were not significantly different between subjects with anxiety disorders only and those without depressive or anxiety diagnoses.
Conclusions: Co-occurring anxiety disorders do not impact performance of depression rating scales in depressed PD patients. However, depression rating scales do not adequately identify anxiety disturbances alone or in patients with depression.
Keywords: Parkinson's disease; anxiety; depression; psychiatric disorder; rating scale.