The assessment of depression in Parkinson's disease

Motor symptoms form the hallmark of Parkinson's Disease (PD), although features like depression are often present. Depression rating scales [e.g. Montgomery-Asberg Depression Rating Scale (MADRS)] used in PD measure affective, cognitive and somatic symptoms. An important clinical question is which items of the MADRS are likely to be influenced by PD symptoms.

Depression was assessed in 43 PD patients who scored below the cut-off of the MADRS and who differed widely in motor severity.

Parkinson's Disease patients scored relatively highest on Concentration difficulties, Reduced sleep and Inner tension. Reduced sleep, Lassitude and Suicidal thoughts were associated with motor severity and specifically with Bradykinesia, Rigidity and Axial impairment, however not with Tremor. To avoid a possible influence on our results of coincidentally included PD patients with a depression, all associations between somatic MADRS items and motor severity were corrected for the influence of affective symptoms of depression. All associations remained significant.

In conclusion, the items Reduced sleep and Lassitude of the MADRS are likely to be influenced by motor symptoms. The high score on Concentration difficulties is suggested to be a reflection of cognitive dysfunction in PD. Thus, when assessing depression in PD, using a depression rating scale like the MADRS, adjusted cut-off scores are required.