Impact of cognitive impairment on the phenomenology of geriatric depression.

OBJECTIVE: Dementia and depressive syndromes demonstrate substantial symptom overlap. As a result, it is challenging to differentiate depression symptoms from nonspecific symptoms of an underlying dementia syndrome. The author addressed the impact of cognitive impairment on the phenomenology of depression symptoms by determining whether more impaired patients were more likely to endorse certain self-report depressive symptoms independent of their underlying level of depression severity. METHODS: Author used data from 576 geriatric rehabilitation inpatients for MIMIC model analyses examining the impact of cognitive impairment on both depression severity and endorsement of symptom clusters. Depressive symptoms were measured with the Geriatric Depression Scale, and cognitive impairment was measured with the Mattis Dementia Rating Scale total score. RESULTS: The reliability (internal consistency) of self-reported depressive symptoms did not change as a function of cognitive impairment. More severe cognitive impairment was associated with greater depression severity but was also associated with two depression symptom clusters after controlling for underlying levels of depression severity. Patients who were more impaired endorsed greater social withdrawal and less psychomotor agitation, independent of their underlying depression severity. Level of cognitive impairment alone did not affect the endorsement of depressed mood and positive affect. CONCLUSIONS: Certain symptoms on depression inventories may be endorsed at a greater level by cognitively impaired patients, independent of their level of underlying depression severity. These symptoms may be nonspecific features of the underlying dementia syndrome and may not be specific to depressive episodes, but instead may represent other syndromes, such as apathy.