Neuropsychological profiles in MCI and in depression: Differential cognitive dysfunction patterns or similar final common pathway disorder?

The concept of "mild cognitive impairment" (MCI) refers to alterations in cognition in the transition between normal aging and dementia. However, from a neuropsychological point of view the conventional diagnostic criteria appear not sufficiently valid. In particular, it is still difficult to differentiate between subjects with MCI and subjects with depression plus cognitive deficits on the basis of their neuropsychological profiles. The aim of this study is to compare cognitive deficit patterns of subjects with MCI and with depression. 24 subjects with MCI, 50 subjects with depression (DEP) and 20 healthy control subjects were included (age: 55-74years). The neuropsychological assessment consisted of standardized tests to assess attention, memory, and executive functions. Compared to healthy controls both subject groups showed significantly lower performance in all cognitive domains. However, we did not find significant differences in cognitive performance between MCI and DEP subjects, neither at baseline nor at follow-up. In addition, preliminary results of follow-up assessments after 2 (DEP) and 6months (MCI), respectively, revealed no significant changes in cognition in subjects with depression, regardless of whether depressive symptoms had improved. Subjects with MCI also showed no changes in cognition at follow-up. The comparable neuropsychological patterns identified in the two subject groups may be understood as a consequence of similar alterations in cognitive systems, supporting the idea of a final common pathway disorder. Thus, the cognitive deficits present in a subgroup of subjects with depression may possibly better be understood in the context of MCI.