The issue of the association between depression and neurocognitive functions is of special interest due to the strong relation between primary depressive symptoms and cognitive impairments, but this relationship in PD is far from clear at present.

To examine the influence of depression on cognitive and speech performance in various stages of PD.

Forty four patients with PD were recruited from the neurology department, University Hospital of Patras in Greece. All patients satisfied PDSBB criteria and dementia was ruled out (MMSE < 24) in all cases. Patients were then divided into six groups, based on severity of PD symptoms and presence of depression. Stage of disease severity was determined using the Hoehn - Yahr Rating Scale. Presence and severity of depression was established using the Beck Depression Inventory and DSM -IV-TR diagnostic criteria for major depressive disorder and dysthymia. Patients were further assessed with a detailed neuropsychological battery and the dysarthria examination battery. All patients were receiving standard medications for their PD symptoms.

Deficits in executive functions, prosody and speech intelligibility were most profound in the late stage depressed PD group. Phonetic impairments were most profound across all stages compared to articulatory and prosodic impairments.

Depressed mood may exacerbate cognitive and speech impairments and affective variables should be an integral part in the treatment of PD in all stages of the disease process, but especially in the later stages.