Recognition of cognitive deficits in old-age depression is especially important since they contribute to poor function outcome, have strong implications for coping abilities and treatment compliance. However, substantial variability in cognitive deficits among older depressed persons has been reported. Clinical and demographic characteristics are likely to have contributed to inconsistencies in previous findings.

To assess effects of unipolar depression on cognitive performance in a population-based sample of elderly persons (60+ years).

An extensive cognitive test battery was administered. Eighty-nine persons fulfilled ICD-10 criteria for unipolar depression (mild, n=48; moderate; n=38, severe; n=3) after thorough screening for dementia (DSM-IV criteria), psychiatric comorbidities, antidepressant pharmacotherapy, and lastly preclinical dementia.

Unipolar old-age depression was associated with deficits in processing speed, attention, executive function, verbal fluency, and episodic free recall. No depression-related deficits were observed in short-term memory, semantic memory, or spatial ability. Increasing age did not exacerbate the cognitive deficits in old-age depression. The cognitive deficits remained significant after exclusion of persons with preclinical dementia, except free recall, where performance differences were at trend level.

Cognitive deficits in unipolar old-age depression involve a number of cognitive domains, and are also present among persons with mild depression. Importantly, no statistically significant performance differences between mild and moderate/severe depression were observed. Given the prevalence of depression in older populations, the impact of this disorder on cognitive functioning may be relatively large at the population level.