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18-07-2013 | Neurology | Article

Subclinical depression causes cognitive self-doubt in Parkinson’s patients


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medwireNews: Patients with Parkinson’s disease (PD) and subclinical depression who complain of cognitive difficulties may not actually have impaired cognition, research suggests.

However, study author Luigi Trojano (Second University of Naples, Caserta, Italy) and team note that even subjective cognitive problems affect patients’ wellbeing.

The researchers identified 30 PD patients with subclinical depression who scored between 9 and 15 on the Beck Depression Inventory (BDI), subsequently confirmed in a clinical interview. This comprised 27.5% of 109 patients screened with the BDI, after excluding six with possible minor depressive disorder.

“Such a high prevalence rate of [subclinical depression] demonstrates its clinical relevance in PD, although identifying depression in PD is difficult due to overlap of its symptoms with core symptoms of PD,” say Trojano et al in the European Journal of Neurology.

Indeed, 10 patients who screened positive on the BDI were nondepressed according to the clinical interview, while six had only minor symptoms. A further 33 patients had confirmed clinical depression, and 36 were nondepressed.

The depressed patients had significantly lower scores on the Montreal Cognitive Assessment than patients with subclinical depression and nondepressed patients. For the total test, scores were 18.8 versus 21.1 and 22.4, respectively; for executive function, scores were 1.2 versus 2.0 and 2.2.

Objective cognitive function of patients with subclinical depression was no worse than that of nondepressed patients, yet they reported significantly more cognitive complaints on the PD Cognitive Questionnaire, with scores of 4.1 versus 2.1. This was not significantly different from the score in the depressed group of patients, of 5.3 points.

“Our findings might suggest that cognitive complaints reflect the effect of negative mood on subjective perception of cognitive impairments in PD and are not necessarily associated with actual cognitive disorders,” say the researchers.

However, they speculate that subclinical depression and subjective cognitive complaints could be harbingers of clinical depression and impaired cognition, which they say is “a hypothesis to be investigated in future longitudinal studies.”

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Eleanor McDermid, Senior medwireNews Reporter

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