Subthreshold depression and subjective cognitive complaints in Parkinson's disease

BACKGROUND AND PURPOSE: Subthreshold depression (SubD) is characterized by clinically relevant depressive symptoms not meeting criteria for major depression. The possible association of SubD with subjective cognitive complaints and/or objective cognitive impairments was investigated in a sample of consecutive, non-demented Parkinson's disease (PD) outpatients. METHODS: Amongst 115 patients, SubD was identified in 30 patients, major depression in 33; 36 patients were classified as non-depressed. Enrolled patients were administered tests and questionnaires validated in PD for assessing objective and subjective cognitive dysfunctions. RESULTS: On objective cognitive measures SubD patients did not differ from non-depressed patients, whereas depressed patients achieved significantly lower scores than the other two groups. SubD and depressed patients reported more cognitive complaints than non-depressed patients. CONCLUSIONS: SubD is a non-motor aspect of PD that is not related to objective cognitive deficits but is associated with subjective cognitive complaints, thus impacting on patients' well-being.