Abstract
Background: Depression is now recognised as not only a disturbance of mood, but also of movement and cognition. In spite of this, cognitive deficits in depressed patients have been poorly differentiated and frequently seen as an epiphenomenon of the disorder.
Aims: To review the cognitive deficits reported in depression and the conceptual frameworks which have been utilised to further our understanding of these deficits in this disorder. Secondly, to review the assumption made in many studies that deficient neurocognitive function will reveal the nature of the defective neuroanatomical regions or pathways underlying psychiatric disorder in general and depression in particular.
Method: A review of the literature was performed using Medline and Psylit earches, focussing particularly on methodologically rigorous studies of cognitive function in depression.
Results: There is now mounting evidence to suggest that the cognitive deficits seen in depression occur independent of age; severity and subtype of depression; task difficulty and response bias and that, in some cases, they may persist upon recovery of the pathological mood, both in younger and older patients. While mnemonic deficits have been well documented, recent studies also suggest the presence of a selective frontal impairment in set-shifting tasks seen across the spectrum of depressive disorders.
Conclusions: Although cognitive deficits do not appear to be an epiphenomenon of depressive disorder, the impact of motivation and recovery upon the cognitive deficits seen in depression require further clarification. Future studies combining functional imaging with a rigorous neurocognitive approach may help elucidate the neuroanatomical basis for these deficits in depression.