Can digit symbol-verbal fluency comparisons facilitate detection of pseudodementia?

Abstract

Depressive psychomotor retardation may impair performance on timed tests. By comparison word association measures of verbal fluency are reportedly unaffected by depression. Comparisons of a brief psychomotor test with a measure of verbal fluency may therefore prove useful when there is a concern that depression may be undermining adaptive functioning, assuming both measures display: (1) broad-spectrum sensitivity to brain impairment, (2) differential vulnerability to depression, and (3) moderate correlation in nondepressed persons. Digit Symbol (DS) and the “FAS” measure of verbal fluency are sensitive to genuine dementia, satisfying the first criterion. We found that depressed schizophrenics performed at significantly lower levels on DS, but not on FAS, than nondepressed schizophrenics. The two groups differed significantly on a discrepancy score derived by subtracting FAS from DS scores; normals obtained discrepancy scores highly similar to those of nondepressed schizophrenics. As the normals had higher DS and FAS scores, this discrepancy-score similarity suggests that this index may have wide application. The third criterion is satisfied by the findings of a 0.64 correlation between DS and FAS scores adjusted for age (DS and FAS) as well as gender and educational attainment (FAS) in nondepressed samples. Implications for further research and clinical applications are discussed.